Title: Florida Entomologist
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Title: Florida Entomologist
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Creator: Florida Entomological Society
Publisher: Florida Entomological Society
Place of Publication: Winter Haven, Fla.
Publication Date: 1993
Copyright Date: 1917
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Subject: Florida Entomological Society
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Insects -- Florida -- Periodicals
Insects -- Periodicals
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(ISSN 0015-4040)


FLORIDA ENTOMOLOGIST

(An International Journal for the Americas)

Volume 76, No. 2 June, 1993

TABLE OF CONTENTS


SYMPOSIUM: CARIBBEAN FRUIT FLY '91

GREANY, P. D., AND C. RIHERD-Preface: Caribbean Fruit Fly Status,
Economic Importance, and Control (Diptera:Tephritidae) .................... 209
SHARP, J. L.-Heat and Cold Treatments for Postharvest Quarantine Disinfesta-
tion of Fruit Flies (Diptera: Tephritidae) and Other Quarantine Pests .... 212
McDONALD, R. E., W. R. MILLER, AND E. J. MITCHAM-Temperature as a
Quarantine Treatment of Caribbean Fruit Flies (Diptera: Tephritidae) and
Its Effect on Product Condition and Quality ..................................... 218
SMITTLE, B. J.-Irradiation ofAnastrepha suspense (Diptera: Tephritidae): New
Irradation Facility ......................................................................... 224
SIMPSON, S. E.-Caribbean Fruit Fly-Free Zone Certification Protocol in
Florida (Diptera: Tephritidae) ....................................................... 228
HEATH, R. R., N. D. EPSKY, P. J. LANDOLT, AND J. SIVINSKI-Development of
Attractants for Monitoring Caribbean Fruit Flies (Diptera: Tephritidae) .... 233
BARANOWSKI, R., H. GLENN, AND J. SIVINSKI-Biological Control of the Carib-
bean Fruit Fly (Diptera: Tephritidae) ............................................... 245
HOLLER, T. C., AND D. L. HARRIS-Efficacy of Sterile Releases of Caribbean
Fruit Flies (Diptera: Tephritidae) Against Wild Populations in Urban
Hosts Adjacent to Commercial Citrus ............................................... 251
GREANY, P. D., AND J. P. SHAPIRO-Manipulating and Enhancing Citrus Fruit
Resistance to the Caribbean Fruit Fly (Diptera: Tephritidae) ................ 258
CALKINS, C. O.-Future Directions in Control of the Caribbean Fruit Fly (Dip-
tera: Tephritidae) ............................................................. 263

SYMPOSIUM: FALL ARMYWORM '92

ROGERS, C. E.- Preface ....................................................... ................. 270
SIMMONS, A. M., AND B. R. WISEMANJames Edward Smith Taxonomic
Author of the Fall Armyworm .......................................................... 271
ROBERTS, P. M., AND J. N. ALL-Hazard for Fall Armyworm (Lepidoptera:
Noctuidae) Infestation of Maize in Double-Cropping Systems Using Sus-
tainable Agricultural Practices ........................................................ 276
WISEMAN, B. R., AND D. J. ISENHOUR-Response of Four Commercial Corn
Hybrids to Infestations of Fall Armyworm and Corn Earworm (Lepidop-
tera: N octuidae) ............................................................................. 283
RIGGIN, T. M., K. E. ESPELIE, B. R. WISEMAN, AND D. J. ISENHOUR-Distri-
bution of Fall Armyworm (Lepidoptera: Noctuidae) Parasitoids on Five
Corn Genotypes in South Georgia ..................................................... 292
Continued on Back Cover


Published by The Florida Entomological Society








FLORIDA ENTOMOLOGICAL SOCIETY

OFFICERS FOR 1992-93
President ............................................. D. F. Williams
President-Elect .................. .................................... J. E. Pefia
Vice-President .............................. .................. E. M. Thorns
Secretary .................. ................. .................. D. G. Hall
Treasurer .............................................................. ................... A. C. Knapp
Other Members of the Executive Committee
J. L. Knapp D. P. Wojcik L. A. Wood J. Hogsette
C. S. Lofgren O. Liburd D. R. Suiter
PUBLICATIONS COMMITTEE
C. S. Lofgren, USDA/ARS (Retired), Gainesville, FL ............................... Editor
Associate Editors
Agricultural, Extension, & Regulatory Entomology
James R. Brown-Disease Vector Ecology & Control Center, NAS, Jacksonville, FL
Richard K. Jansson-Tropical Res. & Ed. Center, UF/IFAS, Homestead, FL
Michael F. Hennessey-Subtropical Horticulture Res. Lab., USDA/ARS, Miami, FL
Geoffrey Zehnder-Auburn University, Auburn, AL
Apiculture
Stephen B. Bambara-North Carolina State University, Raleigh, NC
Biological Control & Pathology
Ronald M. Weseloh-Connecticut Agricultural Experiment Sta., New Haven, CT
John M. Brower-Stored Products Insect Res. Lab., USDA/ARS, Savannah, GA
Book Reviews
J. Howard Frank-Dept. of Entomology, UF/IFAS, Gainesville
Chemical Ecology, Physiology, Biochemistry
Louis B. Bjostad-Colorado State University, Fort Collins, CO
Ecology & Behavior
Sanford D. Porter, Insects Affecting Man Res. Lab., USDA/ARS, Gainesville, FL
Gregory S. Wheeler-Ft. Lauderdale Res. & Ed. Cent. UF/IFAS, Ft. Lauderdale, FL
Forum & Symposia
Genetics & Molecular Biology
Sudhir K. Narang-Bioscience Research Laboratory, USDA/ARS, Fargo, ND
Medical & Veterinary Entomology
Arshad Ali-Central Florida Res. & Ed. Center, UF/IFAS, Sanford, FL
Resumen
J. E. Pefia-Tropical Res. & Ed. Center, UF/IFAS, Homestead, FL
Systematics, Morphology, and Evolution
Michael D. Hubbard-Florida A&M University, Tallahassee, FL
Gary J. Steck-Florida State Collection of Arthropods, Gainesville, FL
Willis W. Wirth-Florida State Collection of Arthropods, Gainesville, FL
Business M manager ....................................................................... A. C. Knapp
FLORIDA ENTOMOLOGIST is issued quarterly-March, June, September, and De-
cember. Subscription price to non-members is $30 per year in advance, $7.50 per copy;
institutional rate is $30 per year. Membership in the Florida Entomological Society,
including subscription to Florida Entomologist, is $25 per year for regular membership
and $10 per year for students.
Inquiries regarding membership and subscriptions should be addressed to the Busi-
ness Manager, P. O. Box 7326, Winter Haven, FL 33883-7326.
Florida Entomologist is entered as second class matter at the Post Office in DeLeon
Springs and in Winter Haven, FL.
Manuscripts from all areas of the discipline of entomology are accepted for consider-
ation. At least one author must be a member of the Florida Entomological Society.
Please consult "Instructions to Authors" on the inside back cover.
This issue mailed June 30, 1993










Caribbean fruit fly '91: Greany & Riherd


209


PREFACE

CARIBBEAN FRUIT FLY STATUS, ECONOMIC
IMPORTANCE, AND CONTROL (DIPTERA: TEPHRITIDAE)

P. D. GREANY1 AND C. RIHERD2
'Insect Attractants, Behavior, and Basic Biology Research Laboratory
Agricultural Research Service
U.S. Department of Agriculture
Gainesville, FL 32604

2Division of Plant Industry
Florida Department of Agriculture and Consumer Services
P.O. Box 147100
Gainesville, FL 32614-7100

ABSTRACT

The history of the Caribbean fruit fly (caribfly), Anastrepha suspense (Loew),in
Florida, its economic status, pre- and post-harvest control measures, and future control
strategies are briefly discussed to introduce a series of more detailed presentations by
authorities on these issues. The initiation and development of the Caribbean Fruit Fly
Protocol (fly-free zone concept) is emphasized





Anastrepha suspense (Loew), became established in Florida in 1965 and within a
few years had spread throughout its potential ecological range, occasionally infesting
more than 80 different fruit and vegetable hosts in the state (Swanson & Baranowski
1972, Von Windeguth et al. 1972). An eradication program was not initiated upon discov-
ery since the fly had been studied for some 30 years in Puerto Rico and had been
observed to cause little damage to citrus fruit, the primary concern in Florida (Anony-
mous 1966; Weems 1966). Also, no suitable attractant was available to delimit the
geographic range of the caribfly, reducing the likelihood of a successful eradication
effort.
We now know that citrus fruit, while not the preferred hosts, may be successfully
attacked by caribfly females, especially when the fruit are senescent (Greany et al.
1985). The primary economic impact of the caribfly has resulted from quarantine restric-
tions imposed on Florida by important domestic and foreign export markets, rather
than from direct yield losses from infested citrus fruit.
When this fly was found infesting commercial grapefruit on March 18, 1968, quaran-
tines were enacted by Arizona, California, Hawaii, and Texas, plus Bermuda and Japan.
Citrus fruit and certain other hosts must now be certified free of the caribfly to be
eligible for shipment to these destinations. Korea also is considering regulations against
the caribfly, causing concern in the citrus industry because this may restrict access to
the increasing market potential in that country. Official letters of protest from the
Florida Department of Agriculture and Consumer Services (FDACS) and the United
States Department of Agriculture (USDA) expressed the view that such an action









210 Florida Entomologist 76(2) June, 1993

would not be biologically justified considering that the Korean climate would be inhos-
pitable for reproduction by the caribfly.
Currently, shipments of grapefruit, orange, lemon, lime and other citrus, plus to-
mato, bell pepper, lychee, mango, avocado, guava, and carambola are affected by
quarantine restrictions. Until 1984, most commodities were disinfested by ethylene
dibromide fumigation, but this was banned at that time by the U. S. Environmental
Protection Agency (EPA). Substantial resources have since been committed by the
State of Florida, the USDA, and the fruit and vegetable industry to develop alternate
methods to certify commodities fly-free, including not only postharvest measures, but
also preharvest control strategies. The various options being pursued for control of the
caribfly are outlined in the papers that follow. These generally fall into either of two
categories: postharvest treatments or preharvest strategies.

POSTHARVEST TREATMENTS

Presently there are three postharvest treatment methods approved for certification
of specific fruits: methyl bromide fumigation, cold treatment and hot water treatment.
Methyl bromide fumigation is approved for citrus and mangos. Cold treatment is ap-
proved for citrus and carambola, and hot water treatment is approved for mangos. All
three postharvest methods present certain difficulties.
Methyl bromide fumigation, conducted in chambers operated by the FDACS, is
being used preferentially for most citrus fruit being shipped to California. However,
recent action by the EPA to abrogate damage to the ozone layer may result in methyl
bromide, like ethylene dibromide, being banned from continued use as a fumigant. Cold
treatment, normally done on board ship due to the time required (10-24 days), can
cosmetically damage early season grapefruit. While hot water treatment has been ap-
proved for certification of mangos, no such facility has been constructed in Florida
because of the limited market for mangos, and no hot water (or hot air) treatment has
been certified for citrus. Temperature management quarantine treatments and their
effect on product condition and quality are described in detail in the following papers
by Sharp and by McDonald et al., respectively.
Use of irradiation as a postharvest treatment to disinfest fruits from the caribfly
also is being explored by the FDACS. Construction of an irradiation facility for this
purpose is described in the paper by Smittle. There also is a private commercial facility
(Vindicator Inc., Mulberry, FL) interested in performing fruit irradiation.

PREHARVEST STRATEGIES THE FLY-FREE ZONE CONCEPT

Along with the approved postharvest treatments, the FDACS is certifying grape-
fruit and oranges from production areas if they are certified to be free of the caribfly.
Production areas can be certified based on combinations of the following approaches:
(1) geographic separation of the production area from infested areas, plus (2) use of
prophylactic malathion bait sprays, or (3) trapping systems that verify the absence of
fly infestation ("negative trapping"). Also, fruit from certified areas must be properly
labelled to prevent co-mingling with fruit from non-certified areas. Development of the
Caribfly Fly-Free Zone Certification Protocol is described in detail in the paper contri-
buted by S. Simpson. During the 1990-91 season, almost 9 million cartons of citrus
valued at over $110 million were certified from 111,020 acres (note added in proof: this
increased to over 151,000 acres certified during the 1992-1993 season). The annual cost
of this certification is approximately $1 million, which is fully supported through grower
participation fees of $3.00 per acre per month.










Caribbean fruit fly '91: Greany & Riherd


One of the criteria used in certifying a grove as being fly-free is the use of "negative
trapping" for fruit fly adults in the grove. Currently, McPhail traps baited with food
attractants are used for this purpose, but better attractants and traps are needed.
Heath et al. contributed a paper describing development of better attractants for
monitoring the caribfly in and around groves, as well as food, pheromone, visual, and
acoustical cues.
Research on biorational methods to reduce populations of the caribfly in citrus grow-
ing regions of Florida also is being performed as a complement to the fly-free approach.
This includes caribfly population reduction through use of augmentative releases of fruit
fly parasites and/or sterile fly releases, as described in the papers by Baranowski et al.,
and by Holler and Harris, respectively.
Research to enhance and extend the innate, early-season resistance of citrus fruit
to attack by the caribfly is described in a paper by Greany and Shapiro. Finally, future
directions likely to be taken for control of the caribfly are described in the paper by
Calkins. Overall, this set of papers encompasses many of the active research areas
directed toward improved control of or coexistence with the caribfly.
The caribfly has had considerable economic impact on the State of Florida, despite
its infrequent attack on commercial citrus fruit. However, the billions of dollars of
economic gain achieved from finding ways to manage the caribfly since its establishment
in Florida in 1965 offsets the millions of dollars that have already been spent in finding
ways to deal with this pest.

REFERENCES CITED

ANONYMOUS. 1966. Researchers seek key to caribfly. Division of Plant Industry News
Bulletin. 8: 1-4.
BENSCHOTER, C. A. 1984. Low-temperature storage as a quarantine treatment for the
Caribbean fruit fly (Diptera: Tephritidae) in Florida citrus. J. Econ. Entomol.
77: 1233-1235.
GREANY, P. D., P. E. SHAW, P. L. DAVIS, AND T. T. HATTON. 1985. Senescence-re-
lated susceptibility of Marsh grapefruit to laboratory infestation by Anastrepha
suspense (Diptera: Tephritidae). Florida Entomol. 68: 144-150.
GREANY, P. D., R. E. MCDONALD, W. J. SCHROEDER, AND P. E. SHAW. 1991.
Improvement in efficacy of gibberellic acid treatments in reducing susceptibility
of grapefruit to attack by the Caribbean fruit fly. Florida Entomol. 75: 570-580.
SWANSON, R. W., AND R. M. BARANOWSKI. 1972. Host range and infestation by the
Caribbean fruit fly, Anastrepha suspense (Diptera: Tephritidae) in South
Florida. Proc. Florida State Hort. Soc. 85: 271-274.
VON WINDEGUTH, D. L., PIERCE, W. H., AND L. F. STEINER. 1972. Infestations of
Anastrepha suspense in fruit on Key West, Florida, and adjacent islands. Florida
Entomol. 56: 127-131.
WEEMS, H. V., JR. 1966. The Caribbean fruit fly in Florida. Proc. Florida State Hort.
Soc. 79: 401-403.









Florida Entomologist 76(2)


HEAT AND COLD TREATMENTS FOR POSTHARVEST
QUARANTINE DISINFESTATION OF FRUIT FLIES (DIP-
TERA: TEPHRITIDAE) AND OTHER QUARANTINE PESTS

JENNIFER L. SHARP
Subtropical Horticulture Research Station
Agricultural Research Service
13601 Old Cutler Road
Miami, FL 33158


ABSTRACT

Heat and cold temperature treatments are used to eliminate pests of quarantine
significance associated with fruits and vegetables; however, the treatments must not
harm the condition or quality of the commodity. Temperature treatments used against
fruit fly pests such as Caribbean fruit fly, Anastrepha suspense (Loew), include expo-
sure to water or air >43C and exposure to cold (0-2.220C). Temperature treatments
used against other pests and plant pathogens are dry heat (>60C) and quick freezing
(-170C or below).


RESUME

Los tratamientos de calor y frio se utilizan para eliminar las plagas asociadas con
frutas y hortalizas y con importancia cuarentenaria. Estos tratamientos no deben dis-
minuir la calidad o condici6n de el material. Los tratamientos cuarentenarios usados
contra la mosca del Caribe, Anastrepha suspense (Loew) incluyen el exponer el material
a el agua o aire a una temperature mayor de 430C o exponerlos a el frio (0-2.220C). Los
tratamientos de temperature utilizados contra otras plagas y patogenos de plants in-
cluyen el calor seco (>600C) y un congelamiento rapido (-17C o menos).





Cold or heat treatments are used for postharvest quarantine to eliminate undesirable
pests, such as the Caribbean fruit fly (caribfly), Anastrepha suspense (Loew), without
injuring the host materials. Critical factors associated with postharvest temperature
treatments are exposure temperature and exposure time. These factors must be deter-
mined and applied precisely because a narrow margin exists between the high or low
temperature needed to kill the pest and the tolerance of the host commodity to the
treatment. Cold treatments include exposing commodities to low temperatures (0 -
2.220C) and quick freezing (-170C or below). Heat treatments include exposing com-
modities to >43C.
Regardless of whether heat or cold is used, all quarantine treatments must provide
probit 9 quarantine security (99.9968% mortality). This means that no more than 32
individuals will survive from a treated population of 1,000,000 at the 95% CL (Baker
1939).
The use of cold, quick freezing, dry heat, vapor heat, hot water, and hot air for
quarantine security is discussed. Quarantine treatments used against the caribfly are
emphasized.


June, 1993


212









Caribbean fruit fly '91: Sharp


Cold

Mason & McBride (1934) and Nel (1936) reported the use of sustained cold temper-
ature to kill Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in fruit. The first
large scale cold treatment of fruit in the United States was used during the Mediterra-
nean fruit fly infestation in Florida during 1927-1929 (Richardson 1952). Tests were
conducted during 1935-1939 in Puerto Rico by McAlister on mangoes and guavas in-
fested with West Indian fruit fly, Anastrepha obliqua (Macquart), and Caribbean fruit
fly at 0-2.2C (Burditt & McAlister 1982), but the fruit used in the tests was severely
damaged by cold exposure.
Hatton & Cubbedge (1982) reported significant chilling injury to Florida grapefruit
when the grapefruit was transferred from ambient room temperatures >21.1 C directly
into refrigeration at 1 1 C. They were able to reduce sensitivity to chilling injury by
conditioning the grapefruit at 10 210C for 7 days before storage at the lower temper-
ature. Benschoter (1984) applied the conditioning period to develop a cold storage
quarantine treatment against the caribfly by storing the grapefruit for 7 days at 10 or
15.60C, then reducing the temperature to 1.70C for 7 19 days. The total exposure time
required to provide probit 9 quarantine security was 30 days for grapefruit conditioned
at 10C and 18.6 days for grapefruit conditioned at 15.60C.
Cold treatment is less desirable for early season grapefruit because at this stage of
development the grapefruit is more sensitive to cold than grapefruit harvested later in
the season (Ismail & Grierson 1977). Strict procedures must be followed and precise
data must be maintained during in-transit cold storage treatment because careful atten-
tion is difficult to achieve for a treatment requiring several weeks (Ismail et al. 1986).
Industry requires faster, more reliable and user-friendly treatments, resulting in cur-
rent attempts by researchers to develop heat treatments to disinfest commodities such
as grapefruit.
Gould & Sharp (1990) developed a cold treatment for Florida carambolas against
Caribbean fruit fly eggs and larvae before shipment to California and Japan. Storage
of carambolas at 1.10C for 15 days provided probit 9 quarantine security.
Cold treatment was approved by the Animal and Plant Health Inspection Service,
Plant Protection and Quarantine (APHIS-PPQ), for Mediterranean fruit fly, Mexican
fruit fly, Anastrepha ludens (Loew), and Caribbean fruit fly in citrus; Queensland fruit
fly, Bactrocera tryoni (Froggatt), in apple, pear, and kiwifruit; and lepidopterous pests
such as false codling moth, Cryptophlebia leucotetra (Meyrick), in citrus and cotton bolls
(Anonymous 1992).
QUICK-FREEZING
Quick freezing, the rapid freezing of commodities to -17"C or below, is often used
for fruit and vegetable imports that are processed (Karpati et al. 1983). Quick-freezing
is not used to kill quarantine pests in fresh fruits and vegetables because the treatment
causes cryolysis of cells, which upon thawing, destroys the commodities. Quick freezing
is not approved for avocados with seeds from Mexico, Central America, and South
America, and for mangoes with seeds from Oceania, Hawaii, Southeast Asia, Philip-
pines, and the Republic of South Africa because of the possible presence of seed pests
(Anonymous 1992).

DRY HEAT
Dry heat treatments are usually done in ovens without humidity control and kill
pests by heating commodities at 100C for 1 hour (Karpati et al. 1983). Dry heat can be
used for commodities when the high temperatures needed to kill the pests are tolerated
by the commodity. Pests controlled with dry heat are primarily plant pathogens,


213









Florida Entomologist 76(2)


nematodes, and some insects. Dry heat was approved by APHIS-PPQ for ear corn
treated at 75.5C for 2 hours (Anonymous 1992); rice straws and hulls in groups of
-11.34 kg treated at 100C for 1 hour (Anonymous 1992); feeds and milled products
infested with khapra beetle, Trogoderma granarium Everts, treated at 82.20C during
any part of the processing procedure or at 65.5C for 7 min (Anonymous 1992), and
sweet potato treated at 39.4C for 30 hours to kill infestations of root knot nematode
(Karpati et al. 1983). Dry heat as a quarantine treatment is not applicable for fresh
fruits because the high temperatures would severely damage fruit before pest mortality
occurred.

VAPOR HEAT

Vapor heat treatments involve heating fruit with hot air saturated with water vapor.
Vapor heat was developed by A C. Mason (reported by Baker 1939) to kill Mediterra-
nean fruit fly eggs and larvae in citrus.
Seo et al. (1974) reported probit 9 security against oriental fruit fly, Bactrocera
dorsalis (Hendel), eggs and larvae in Hawaiian papayas using an average 11-hour ap-
proach time to raise the fruit temperatures from 23.3 to 44.4C, followed by maintaining
the fruit temperatures at 44.4C for 8.75 hours. Vapor heat was approved as a quaran-
tine treatment against Mexican fruit fly in grapefruit, orange, tangerine, and mango.
Research for mangoes was done by Balock & Starr (1945). Mexican fruit fly eggs and
larvae are controlled in these commodities by raising the fruit center temperature to
43.30C within 8 hours and maintaining the fruit center temperatures at 43.3C for 6
hours (Anonymous 1992). Vapor heat also was approved as a treatment against Mediter-
ranean fruit fly, oriental fruit fly, and melon fly, Bactrocera cucurbitae (Coquillett), in
bell pepper, eggplant, papayas, tomato, zucchini squash, and some pineapple cultivars
(Armstrong et al. 1979, Anonymous 1992). 'Marsh' grapefruit grown in Florida tolerated
a vapor heat treatment at 43.3 43.7C for 5 hours, although caribfly eggs and larvae
in grapefruit were killed when the grapefruit center pulp were kept at 43.3*C for 50
min (Hallman et al. 1990). Caribfly eggs and larvae in Florida-grown carambola were
killed when carambola was exposed to vapor heat at 46 46.3C for 90 min (Hallman
1990).

HOT AIR

Hot air treatments consist of heating fruit with air in a closed system similar to
vapor heat treatments. The difference is that relative humidity is controlled so that
condensation does not occur on the fruit surfaces (Gaffney & Armstrong 1990; Sharp et
al. 1991). To accomplish this, the dry-bulb temperature is maintained about 2C above
the dew-point temperature. Relative humidity inside the treatment area may vary from
ambient to >80%, thereby reducing desiccation of the commodities during treatment.
A hot air treatment has been developed against caribfly eggs and larvae in Florida
carambola using an air temperature of 47.2C for 1.5 2 hours until fruit center temper-
atures reach -45.50C (Sharp & Hallman 1992). Hot air treatment was approved by
APHIS-PPQ (Anonymous 1989) against Mediterranean fruit fly, oriental fruit fly, and
melon fly in Hawaiian-grown papayas by exposing fruit to 43-490C air temperatures
until the fruit center temperatures reach 47.20C (Armstrong et al. 1989). The treat-
ment was reported superior to a double hot water immersion treatment that caused
hard, unripened areas throughout the pulp (Chan 1986), and did not provide probit 9
quarantine security (Zee et al. 1989). Hot air is a new quarantine treatment that may
be suitable for other commodities, such as citrus, that do not tolerate exposure to hot
water immersion (Miller et al. 1988). Hot air treatment for citrus was shown superior


214


June, 1993










Caribbean fruit fly '91: Sharp 215

to cold treatment primarily because hot air treatment requires a few hours, whereas
cold exposure requires -12 days (Benschoter 1984).


HOT WATER IMMERSION

Hot water immersion treatment is done by immersing the infested commodities in
43 500C water for a time period sufficient to heat the commodity beyond the thermal
mortality limits of the pest. The treatment must provide probit 9 quarantine security
without damaging the commodity. Hot water immersion was used to disinfest Hawaiian
papaya (Couey & Hayes 1986) and banana (Armstrong 1982) of Mediterranean fruit fly,
oriental fruit fly, and melon fly. Couey & Hayes (1986) reported that papayas less than
one-quarter ripe immersed in 42C water for 30 min and then immediately transferred
to 49C water for 20 min caused unacceptable damage characterized by hard areas in
the pulp which would not ripen (Chan 1986). Armstrong (1982) developed a 15 min, 50C
hot-water dip treatment that disinfested 'Brazilian' bananas of Mediterranean fruit fly,
oriental fruit fly, and melon fly. Hot water immersion treatments were used successfully
against caribfly eggs and larvae in Florida mangoes immersed in 46.1C water for 90
min (Sharp et al. 1989a), West Indian fruit fly (Sharp et al. 1988, 1989b; Segarra-Car-
mona et al. 1990), Mexican fruit fly (Sharp et al. 1989b), and Mediterranean fruit fly
(Sharp et al. 1989c, Sharp & Picho-Martinez 1990). Heated water was tried as an immer-
sion quarantine treatment for stone fruits (Sharp 1990), grapefruit (Sharp 1985), and
carambola (Hallman & Sharp 1990), but was not recommended for these fruits because
they were damaged by the treatment temperatures and exposure times.

COMBINATION TREATMENT

Gould (1988) used hot water immersion followed by cold storage as a combination
treatment against caribfly eggs and larvae in grapefruit. Probit analysis of the data
estimated that immersion in 43.3C water for 100 min, followed by storage at 1.1C for
7 days, would provide quarantine security. Other combination treatments used against
caribfly infestations in host materials are cold storage and non-temperature manage-
ment methods such as gamma irradiation for grapefruit (von Windeguth & Gould 1990),
methyl bromide fumigation and cold storage for peaches, nectarines, and plums
(Benschoter 1988), and grapefruit (Benschoter 1982). Modified atmospheres, such as
altered concentrations of carbon dioxide and oxygen and cold storage, have been used
for eggs and larvae in laboratory diet (Benschoter 1987).


CONCLUSION

APHIS-PPQ has approved temperature management quarantine treatments that do
not damage the commodities and provide probit 9 quarantine security against many
different pest species. These treatments are published as schedules in the treatment
manual that was cited often in this paper (Anonymous 1992). Temperature treatments
are environmentally safe and no chemical or toxic residues are generated. Temperature
treatments include hot water immersion for mango, carambola, and banana; vapor heat
for papaya, mango, carambola, citrus, and some vegetables; hot air for papaya, caram-
bola, citrus, and mango; and cold storage for citrus, pome fruits, stone fruits, grape,
and persimmon. Because of increasing pressures by consumers who refuse to purchase
foods that have been treated with chemicals, especially methyl bromide, temperature
management will increase as a the preferred method to disinfest commodities of
quarantine pests.









216 Florida Entomologist 76(2) June, 1993

END NOTE

SMention of a commercial or proprietary product does not constitute endorsement
by the U.S. Department of Agriculture.

REFERENCES CITED

ANONYMOUS. 1989. Animal and Plant Health Inspection Service. Plant pest and
quarantine treatment manual. Incorporation by reference. Rules and regulations.
Federal Register 54: 12871-12873.
ANONYMOUS. 1992. Animal and Plant Health Inspection Service. Plant protection and
quarantine treatment manual. U.S. Govt. Printing Office. Washington, D.C.
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Caribbean fruit fly '91: Sharp


bolas infested with the Caribbean fruit fly (Diptera: Tephritidae). J. Econ. En-
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218 Florida Entomologist 76(2) June, 1993

SHARP, J. L., M. T. OUYE, S. J. INGLE, AND W. G. HART. 1989b. Hot-water quaran-
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SHARP, J. L., M. T. OUYE, S. J. INGLE, W. G. HART, W. R. ENKERLIN H., H.
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SHARP, J. L., M. T. OUYE, R. THALMAN, W. HART, S. INGLE, AND V. CHEW. 1988.
Submersion of 'Francis' mango in hot water as a quarantine treatment for the
West Indian fruit fly and the Caribbean fruit fly (Diptera: Tephritidae). J. Econ.
Entomol. 81: 1431-1436.
SHARP, J. L. AND H. PICHO-MARTINEZ. 1990. Hot-water quarantine treatment to
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VON WINDEGUTH, D. L. AND W. P. GOULD. 1990. Gamma irradiation followed by cold
storage as a quarantine treatment for Florida grapefruit infested with Caribbean
fruit fly. Fla. Entomol. 73: 242-247.
ZEE, F. T., M. S. NISHINA, H.T. CHAN, JR. AND K. A. NISHIJIMA. 1989. Blossom
end defects and fruit fly infestation in papaya following hot water quarantine
treatment. HortScience 24: 323-325.







TEMPERATURE AS A QUARANTINE TREATMENT OF
CARIBBEAN FRUIT FLIES (DIPTERA: TEPHRITIDAE) AND
ITS EFFECT ON PRODUCT CONDITION AND QUALITY

ROY E. MCDONALD, WILLIAM R. MILLER, AND ELIZABETH J. MITCHAM
U.S. Horticultural Research Laboratory
Agricultural Research Service
2120 Camden Road
Orlando, FL 32803

ABSTRACT

Temperature management treatments have been tested for disinfestation of com-
modities containing eggs and larvae of the Caribbean fruit fly, Anastrepha suspense
(Loew). Some of these treatments have reduced the quality of horticultural com-
modities, while others have had no deleterious effects. Hot water immersion, vapor
heat, hot air, and cold storage are reviewed with respect to their effect on the market
quality attributes of several fruits.

RESUME

Se ha experimentado con los tratamientos de manejo de temperature para la desin-
festaci6n de frutas con huevos y larvas de la mosca del Caribe, Anastrepha suspense
(Loew). Algunos de estos tratamientos han reducido la calidad de los products hor-









Caribbean fruit fly '91: McDonald et al. 219

ticolas, mientras que otros no han mostrado efectos nocivos. Se revisan los tratamientos
de imersi6n en agua caliente, vapor caliente, aire caliente, y almacenamiento en frio,
con respect a su efecto en la calidad y otros atributos de varias frutas.




Quarantine treatments for horticultural commodities must be efficacious and not
adversely affect the commodity's quality, condition, and susceptibility to decay. Con-
sumers may not be willing to pay as high a price for lower quality, and competition from
sources not requiring quarantine procedures may gain a marketing advantage. There-
fore, any treatment used to disinfest a commodity should have minimal deleterious
effects on the market quality attributes of that commodity.
Heat and cold treatments are being tested for insect disinfestation purposes primar-
ily because they are efficacious, nonresidual and noncarcinogenic and, therefore, have
a much greater chance of being approved for use by regulatory agencies as compared
with chemical treatments. The emphasis with tropical and subtropical commodities has
been on heat treatments instead of cold treatments because their sensitivity to temper-
atures less than 10C makes cold treatments inappropriate. However, cold treatments
have been used successfully on some commodities.
Several types of temperature treatments have been studied for the purpose of disin-
festation of commodities infested with the Caribbean fruit fly (caribfly), Anastrepha
suspense (Loew) (Table 1). We will first discuss the response of various fruits to heat
treatments with respect to compromising their condition and quality. The quality of a
horticultural commodity refers to many different things depending on the commodity.
Quality is best used with reference to palatability, or a pleasing combination of flavor
and texture. Condition refers to the presence of, or freedom from, disease, injury, or
physiological disorders.
Heat treatments can be applied as hot water immersion, vapor heat, or hot air.
Vapor heat is applied directly to the surface of fruits by condensation of water vapor
on the fruit.
Individual commodities respond differently to the stresses imposed by physical
quarantine treatments. Deleterious commodity responses may be conspicuous and ap-
pear immediately following treatment or only after a storage or marketing period.
Damage includes abnormal weight loss, pulp softening, peel discoloration, surface le-
sions, and increased decay. Some responses are physiological in nature occurring espe-
cially in those commodities that are mature at the time of treatment, but ripen after
treatment. Symptoms of this response in these climacteric fruits include atypical peel
or pulp color, nonuniform softening, abnormal texture, and off flavors. We will review
only those quarantine treatment studies that evaluate the resulting condition or quality
of the product as a result of a disinfestation treatment for the caribfly. It is important
to note that many factors affect the susceptibility of individual commodities to damage
from quarantine heat treatments. These factors include cultivar, fruit size, maturity,
lapsed time between harvest and treatment, and storage conditions after treatment.


HOT WATER IMMERSION

Immersing both tart and sweet carambolas in 46-46.4C water for 55-85 min ad-
versely affected their market quality (Hallman 1989, Hallman & Sharp 1990). A few
days after treatment, tart carambolas turned a dull yellow and became soft. Shelf life
of sweet carambolas was reduced 2-4 d by the treatment. Hallman (1991) reported that
water immersion at 49-49.3C for 25 or 35 min resulted in excessive damage to caram-









Florida Entomologist 76(2)


TABLE 1. RESPONSE OF HORTICULTURAL COMMODITIES TO TEMPERATURE MAN-
AGEMENT QUARANTINE TREATMENTS AGAINST THE CARIBBEAN FRUIT
FLY WITH RESPECT TO DAMAGE.

Commodity Treatment Damage Reference

Carambola Hot water Yes Hallman (1989)
Carambola Hot water Yes Hallman & Sharp (1990)
Carambola Hot water Yes Hallman (1991)
Carambola Hot air Yes Miller et al. (1990)
Carambola Vapor heat No Hallman (1990)
Carambola Vapor heat Yes Hallman (1991)
Carambola Cold No Gould & Sharp (1990)
Grapefruit Cold No Hatton & Cubbedge (1982)
Grapefruit Cold No Hatton & Cubbedge (1983)
Grapefruit Cold No Benschoter (1983)
Grapefruit Hot water Yes Sharp (1985)
Grapefruit Hot water Yes Miller et al. (1988)
Grapefruit Hot water Yes Miller et al. (1989)
Grapefruit Vapor heat Yes Miller et al. (1989)
Grapefruit Vapor heat No Hallman et al. (1990)
Grapefruit Vapor heat No Miller et al. (1991b)
Grapefruit Hot air No Sharp (1989)
Mango Hot water No Spalding et al. (1988)
Mango Hot water No Sharp (1986)
Mango Hot water No Sharp & Spalding (1984)
Mango Hot water No Sharp et al. (1988)
Mango Hot water No Sharp et al. (1989)
Mango Hot air No Miller et al. (1991a)
Nectarine Hot water Yes Sharp (1990)
Peach Hot water Yes Sharp (1990)
Plum Hot water Yes Sharp (1990)



bolas, but there was no difference in marketability of fruit treated at 43.3-43.60C for 55
or 70 min or at 46-46.30C for 35 or 45 min compared with controls.
Sharp (1990) found that immersing California nectarines, plums, and peaches in
49.4-50C water for 5-25 min resulted in unacceptable market quality. Regardless of
cultivar, the treated stone fruits displayed unacceptable amounts of pitting, shriveling,
surface scald, and bland flavor compared with control fruits.
Sharp (1985) reported that 'Marsh' grapefruit immersed in 48.90C water for 20 min
or longer exhibited severe scalding and pitting and produced off-flavors compared with
control fruit. Miller et al. (1988, 1989) found that immersing 'Marsh' grapefruit in 43.5C
water for 4.5 h caused peel discoloration, puffiness, and decreased resistance of peel to
penicillium infection.
Immersion of'Tommy Atkins' and 'Keitt' mangos in 46. 1C water for 65 min reduced
the incidence of mango stem-end rot and anthracnose without significantly affecting
fruit quality (Sharp & Spalding 1984). Lenticels were darker on 'Tommy Atkins' im-
mersed in 46C water for 120 min, on 'Keitt' immersed in 46C water for 90 min, and
on both cultivars immersed in 49C water for 60 min (Spalding et al. 1988). However,
immersion of mangos in water at 460C for 60-90 min did not reduce market quality
(Spalding et al. 1988). In subsequent tests, Sharp (1986) reported immersion in water


220


June, 1993










Caribbean fruit fly '91: McDonald et al. 221

at 46.1-46.7C for 45-65 min produced no visible injury to 'Tommy Atkins' or 'Keitt'
mangos. However, the percentage of acceptable 'Francis' mangos decreased as the
length of immersion time at 46.1-46.70C increased beyond 75 min (Sharp et al. 1988).
Immersion of 'Tommy Atkins' and 'Keitt' mangos in water at 46.1-46.7C for 90 min was
shown by Sharp et al. (1989) to be an effective quarantine treatment that did not cause
a reduction in fruit quality.


VAPOR HEAT

Hallman (1990) reported that carambolas treated at 49-49.3C for 3.75 h showed
extensive scalding after 2-3 d and were unmarketable. Carambolas treated with vapor
heat at 43.3-43.60C for 90 or 120 min and 46-46.3C for 60 or 90 min appeared slightly
darker and duller, and rib margins were darker than on control fruit but were still
considered marketable (Hallman 1990). Vapor heat at 49-49.30C for 45 or 60 min caused
considerable brown spotting and scalding of carambolas after treatment and the fruit
were considered unmarketable (Hallman 1991).
Hallman et al. (1990) reported that vapor heat at 46-46.4C for 3.75 h resulted in
darkening of the oil glands of 'Marsh' grapefruit peel and increased the susceptibility
of the fruit to storage decay compared with control fruit. However, in a nonreplicated
test, Hallman et al. (1990) reported vapor heat at 43.3-43.70C for 5 h caused no damage
to freshly harvested grapefruit. Miller et al. (1989) reported development of scald on
vapor heat-treated fruit at 43.50C for 4.25 h in a preliminary, nonreplicated test. How-
ever, in later replicated tests, Miller et al. (1991b) reported that similar vapor heat
conditions actually reduced peel pitting 5-fold compared with control fruit after 5 weeks
of storage and did not cause peel discoloration or rind breakdown.


HOT AIR

Sharp (1989) found that the quality of 'Marsh' grapefruit treated at 46C for 3 h was
not reduced, and no differences were observed between treated and control fruit. The
hot air treatment appliance is described by Gaffney & Armstrong (1990).
To establish the threshold boundary for stress tolerance of carambolas to hot air,
Miller et al. (1990) treated fruit at 47, 48 and 490C for 90, 120 or 150 min. They found
that treated carambolas deteriorated more rapidly, lost more weight, had more stem-
end breakdown and rib-browning, and generally had a more undesirable flavor than
nontreated fruit. They found treatment temperatures above 470C were not acceptable
at the treatment durations of 90, 120 or 150 min. Generally, treatment at 470C for 90
to 120 min is probably near the threshold for stress that carambolas can tolerate.
Miller et al. (1991a) reported that mangos treated with forced air at 51.50C for 125
min lost 1.0% more fresh weight than nontreated fruit and developed trace amounts of
peel pitting. Total soluble solids concentrations were similar for treated and nontreated
fruit, as was peel color at the soft-ripe stage (Miller et al. 1991a). Treated fruit generally
reached the soft-ripe stage about 1 d earlier than nontreated fruit and had a lower
incidence and severity of stem-end rot and anthracnose. The authors felt that the trace
of pitting on treated fruit probably would not influence consumer acceptance.
Mitcham & McDonald (unpublished data) found that similar treatment of 'Keitt' and
'Tommy Atkins' mangos with hot air at 51.5C for 125 min reduced the rate of respiration
of the fruit; however, the respiratory climacteric occurred at the same time as control
fruit. Heated fruit also softened at a reduced rate as compared to controls and had a
much lower incidence of antracnose decay. These effects may be beneficial to the post-
harvest shelf life of mango.









222 Florida Entomologist 76(2) June, 1993


COLD STORAGE

Hatton & Cubbedge (1982) established that 'Marsh' and 'Ruby Red' grapefruit could
be stored at 1C for 21 d without suffering chilling injury if the fruit were first temper-
ature-conditioned for 7 d at 10, 16 or 21C. Further research showed that conditioning
grapefruit at 21 or 27C for 7 d was significantly less effective than conditioning for a
similar period of time at 16C (Hatton & Cubbedge 1983). Based on this research,
Benschoter (1983) reported that storage of grapefruit infested with caribfly and stored
for 14 d at 1.7C resulted in 100% fly mortality.
Gould & Sharp (1990) developed a cold storage quarantine treatment for 'Arkin'
carambolas in which probit 9 was estimated to occur in 13.6 d at 1.1C and in 21.1 d at
5C. They found that storage of carambolas at 1.1C up to 15 d caused little or no
damage to the fruit.


CONCLUSION

The use of temperature management as a quarantine treatment has been proved to
be effective against the caribfly. Temperature management quarantine treatments
which do not reduce product condition or quality and are approved for use by the Animal
and Plant Health Inspection Service of the U.S. Department of Agriculture are: cold
treatment for carambola; cold treatment and vapor heat for grapefruit; and hot water
for mango (Table 2). In addition, our experimental testing indicates hot air is effective
as a quarantine treatment for 'Tommy Atkins' mangos, and vapor heat is effective for
Florida grapefruit. Because nonchemical treatments do not leave chemical residues,
they can be quickly approved and adopted by the industry.
However, even with approved treatments, injury does occur at times under commer-
cial conditions. Investigations are continuing to determine the influence of fruit matur-


TABLE 2. TEMPERATURE MANAGEMENT QUARANTINE TREATMENTS THAT PRO-
VIDE QUARANTINE SECURITY AGAINST THE CARIBBEAN FRUIT FLY AND
DO NOT REDUCE THE CONDITION OR QUALITY OF COMMODITIES.

Approved
Commodity/cultivar Treatment' by APHIS2

Carambola,'Arkin' VH 43.3-43.6C, 90 or 120 min; No
VH 46-46.3C, 60 or 90 min No
Carambola, 'Arkin' C 1.1C, 15 d Yes3
Grapefruit, 'Ruby Red' 'Marsh' C 16C, 7 d + 1.7C, 14 d Yes
Grapefruit, 'Marsh' VH 43.3-43.7C, 5 h; Yes
VH 43.50C, 4.25 h Yes
Grapefruit, 'Marsh' HA 46C, 3 h No
Mango, 'Tommy Atkins' 'Keitt' HW 46C, 60-90 min; Yes
HW 46.1-46.7C, 75 min Yes
Mango, 'Francis' HW 46.1-46.70C, 1.25-2 h Yes
Mango, 'Tommy Atkins' 'Keitt' HW 46.1-46.7C, 90 min Yes
Mango, 'Tommy Atkins' HA 51.5C, 125 min No

'VH = vapor heat, C = cold, HA = hot air, and HW = hot water.
'Animal and Plant Health Inspection Service of the U.S. Department of Agriculture. 1976. (revised 1985). Plant
Protection and Quarantine Treatment Manual, Section VI-T100. Animal and Plant Health Inspection Service, U.S.
Department of Agriculture, Washington, D.C.
'For domestic shipments only.









Caribbean fruit fly '91: McDonald et al.


ity, time after harvest and post-treatment storage conditions on susceptibility to injury.
Continued research seeks to further refine the currently approved treatments and to
develop alternative treatments for these and other commodities. For example, prelim-
inary data (Miller & McDonald) indicate that preharvest application of gibberellic acid
will abrogate damage that may be due to vapor heat treatment of grapefruit. It is
important that treatments developed under experimental conditions be feasible in a
commercial setting. The treatment protocol must tolerate the increased variability in
commodity condition and treatment temperature and time which occur under commer-
cial conditions without leading to commodity injury or fruit fly survival.

REFERENCES CITED

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fruit fly in grapefruit. Proc. Fla. State Hort. Soc. 96: 318-319.
GAFFNEY, J. S., AND J. W. ARMSTRONG. 1990. High-temperature forced-air research
facility for heating fruits for insect quarantine purposes. J. Econ. Entomol. 83:
1959-1964.
GOULD, W. P., AND J. L. SHARP. 1990. Cold-storage quarantine treatment for caram-
bolas infested with the Caribbean fruit fly (Diptera: Tephritidae). J. Econ. En-
tomol. 83: 458-460.
HALLMAN, G. J. 1989. Quality of carambolas subjected to hot-water immersion quaran-
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fruit fly (Diptera: Tephritidae). J. Econ. Entomol. 83: 2340-2342.
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Entomol. 83: 1475-1478.
HALLMAN, G. J., AND J. L. SHARP. 1990. Hot-water immersion quarantine treatment
for carambolas infested with Caribbean fruit fly (Diptera: Tephritidae). J. Econ.
Entomol. 83: 1471-1474.
HATTON, T. T., AND R. H. CUBBEDGE. 1982. Conditioning Florida grapefruit to reduce
chilling injury during low-temperature storage. J. Amer. Soc. Hort. Sci. 107:
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HATTON, T. T., AND R. H. CUBBEDGE. 1983. Preferred temperature for prestorage
conditioning of 'Marsh' grapefruit to prevent chilling injury at low temperatures.
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MILLER, W. R., R. E. MCDONALD, T. T. HATTON, AND M. ISMAIL. 1988. Phytotoxic-
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MILLER, W. R., R. E. MCDONALD, G. L. HALLMAN, AND M. ISMAIL. 1989.
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224 Florida Entomologist 76(2) June, 1993

of Florida grapefruit after exposure to vapor-heat quarantine treatment.
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West Indian fruit fly and the Caribbean fruit fly (Diptera: Tephritidae). J. Econ.
Entomol. 81: 1431-1436.-
SHARP, J. L, M. T. OUYE, W. HART, S. INGLE, G. HALLMAN, W. GOULD, AND V.
CHEW. 1989. Immersion of Florida mangos in hot water as a quarantine treat-
ment for Caribbean fruit fly (Diptera: Tephritidae). J. Econ. Entomol. 82: 186-
188.
SHARP, J. L., AND D. H. SPALDING. 1984. Hot water as a quarantine treatment for
Florida mangos infested with Caribbean fruit fly. Proc. Fla. State Hort. Soc. 97:
355-357.
SPALDING, D. H., J. R. KING, AND J .L. SHARP. 1988. Quality and decay of mangos
treated with hot water for quarantine control of fruit fly. Trop. Sci. 28: 95-101.








IRRADIATION OF ANASTREPHA SUSPENSE (DIPTERA:
TEPHRITIDAE): NEW IRRADIATION FACILITY

BURRELL J. SMITTLE
Florida Department of Agriculture and Consumer Services
Division of Plant Industry
P.O. Box 147100
Gainesville, FL 32614

ABSTRACT

An irradiation facility financed by a Cooperative Agreement with the U.S. Dept. of
Energy, is near completion in Gainesville, FL. It utilizes a GE-CGR linear accelerator
as the irradiation source in a two level design. The lower level has a one meter horn
for 10 MeV electrons to irradiate shallow layers of commodities. The upper level has a
2.5 meter horn equipped to produce 5 MeV X-rays to irradiate loads up to pallet size.
Automated conveyors transport materials to be irradiated. The facility is divided for
irradiated and unirradiated commodities with freezer and refrigerated storage on both
sides. The facility is designed for both research and demonstration purposes and has
the capacity to irradiate over 10 million Caribbean fruit fly larvae or pupae per minute.









Caribbean fruit fly '91: Smittle


RESUME

Se va a inaugurar proximamente en Gainesville, Florida una plant de irradiaci6n
financiada por el Pacto Cooperativo con el depto de Energia del USDA. Esta plant
utiliza un acelerador linear GE-CGR como la fuente de irradiaci6n en 2 niveles de
disefio. El nivel bajo tiene un cuerno de 1 m con 10 Mev de electrones para irradiar la
parte externa del product a tratar. El nivel superior tiene un cuerno de 2.5 m el que
produce 5 Mev rayos X para irradiar cargamentos del tamafo de una paleta. Transpor-
tadores automaticos transportan los materials para ser irradiados. Esta plant esta
dividida en varias areas: almacenamiento de products irradiados y no irradiados con
su respective congelador y refrigerator en ambos lados. Esta plant ha sido designada
para investigaciones y demostraciones y tiene la capacidad de irradiar mas de 10 millones
de larvas o pupas de la mosca del Caribe por minute.





The reappearance of the Caribbean fruit fly (caribfly), Anastrepha suspense (Loew),
in Florida in 1965 came at a time when the use of irradiated males was proving to be
successful in the control of other fruit flies. Therefore, in addition to chemical control
studies, research on the use of the sterile insect technique to control this fly was started
within a short time after its reappearance.
In 1970, Lopez reported on preliminary tests with irradiation that indicated 100%
male sterility at 8 kR. In Key West, Florida, beginning in 1970, a sterile caribfly release
test was conducted cooperatively by the U. S. Department of Agriculture (USDA),
University of Florida Agricultural Research and Education Center at Homestead, and
the Florida Department of Agriculture and Consumer Services, Division of Plant Indus-
try (FDACS/DPI). During the 16-month test, 61 million irradiated flies were released.
Declines in the trap catches and fruit infestations indicated that the sterile male insect
release method should be applicable for suppression or eradication of the caribfly as it
had been with other fruit flies (Burditt et al. 1974). Since this release study, many other
studies have been conducted in Florida relating to the use of sterile males for control
of the caribfly by the three groups involved.
In 1980, the U. S. Environmental Protection Agency (EPA) notified the citrus indus-
try and agencies involved with the use of ethylene dibromide (EDB) for fumigation of
citrus fruit that continued registration of EDB was not assured and that alternative
certification procedures must be examined prior to extension of registration. The EPA
named several alternatives and specifically stated that irradiation should be considered.
This action prompted federal, state, and private industry scientists to initiate research
to find alternative methods to certify that Florida citrus and other commodities met
requirements for absence of insect pests and disease.
In addition to research on fly-free zones and cold treatment techniques, investiga-
tions of the use of irradiation for disinfestation of fruit were initiated. Grapefruit was
the primary focus of this research due to its importance in U.S. trade with Japanese
markets. One of the first problems encountered in this cooperative effort was finding a
facility to irradiate grapefruit. The units used by the USDA in Miami and in Gainesville
could irradiate only 2 grapefruit at a time. Tests were conducted with grapefruit in-
fested in Miami, trucked to New Mexico for irradiation, and shipped back to Florida
for evaluation. Hatton et al. (1982) and von Windeguth (1982) reported promising re-
sults, even though only 8 grapefruit could be irradiated at a time. Later, Ismail et al.
(Florida Dept. of Citrus, Lake Alfred, FL; personal communication) shipped grapefruit
to New Jersey and conducted dosimetry studies on irradiating a box of fruit at a time.
They followed up with studies in The Netherlands where 2 pallets of grapefruit at a


225









226 Florida Entomologist 76(2) June, 1993

time were irradiated with a max/min ratio of approximately 2 (maximum dose twice
minimum dose).
Based on promising results, the USDA and the United States Department of Energy
(DOE) planned an irradiation facility in Miami, Florida. In 1984, after the USDA with-
drew from this program, FDACS/DPI filed an official request with DOE to be consid-
ered for an irradiator to be built next to a proposed caribfly mass rearing facility. After
the U. S. Congress provided funds to establish regional demonstration irradiators,
negotiations between DOE and FDACS/DPI led to a 1987 cooperative agreement to
build an irradiation facility in Gainesville, Florida. The conceptual design utilized
cesium-137 as the irradiator source, with DOE supplying the cesium. However, after
General Electric purchased a French company that produced linear accelerators, the
design was changed to utilize a linear accelerator to provide both electrons and X-rays
for irradiation. The total federal funding for the project through the DOE was $5.4
million with additional contributions in funds, personnel, management costs, and land
through the State of Florida. Smittle et al. (1991) reported on the progress and planned
uses of this facility.
The linear accelerator was manufactured by CGR MeV in France. CGR MeV became
a subsidiary of GE-CGR in 1988 and now is part of MeV Industries, Ltd., a joint venture
of Sumitomo Heavy Industries, Ltd. and GE-CGR. The Florida model of the CIRCE
accelerator is equipped with scanning horns on two levels (Figure 1). The lower level
has a one meter horn producing electrons up to 10 MeV at 10 kW to treat shallow layers
of commodities. The upper level has a 2.5 meter horn producing X-rays up to 5 MeV at
20 kW to treat large cartons or pallet loads of commodities. A switching magnet is used
to control the use of either scanning horn, and large electromagnets weighing up to 8000
Ibs are used to direct the electrons to the target. Automated conveying systems were
installed to transport commodities on both levels. The upper conveyor uses a tow-chain
system to transport carts holding 4 x 4 x 6-ft pallets into the irradiation chamber and
past the X-ray beam. An automated system rotates the carts 180 after the first pass
and the carts pass through the irradiation chamber again to provide irradiation from 2
sides. The lower conveyor uses belts, rollers, and a stainless steel chain system to move
cartons under the electron beam. This system allows cartons up to 18 in high and 36 in
wide to be irradiated. All components of the accelerator have been assembled and
following modification of the switching magnet, the power-up sequence will be com-
pleted.
The facility has over 13,000 ft2 including the lower irradiation area and a mezzanine
equipment area. The shield area utilized over 1,000,000 lbs of concrete and over 50,000
lbs of steel. The wall separating the linear accelerator from the operations area is almost
10 ft thick. The outside walls of the shield are 2 ft thick and the roof is 3 ft thick. The
entire shield area is covered with 15 ft of soil to provide adequate shielding for the


0 10 2 X W RE
. . . . . 'In


Fig. 1. Longitudinal Section of Florida Agricultural Commodities Irradiator









Caribbean fruit fly '91: Smittle


X-rays. A 70 x 102 ft metal building provides space for the equipment and operations
area. The majority of the area is open to provide space to store and handle pallet loads
of commodities. The area has an 8 ft high chain-link fence down the center, dividing the
space into areas for irradiated and nonirradiated commodities. Both areas contain
freezer and refrigerator space. This area also contains the control room, dosimetry
laboratory, manager's office, shipping office, and rest rooms. The versatile design allows
application to a host of agricultural commodities and meets processing requirements for
foods as well as non-food items. A loading dock is accessible through large overhead
doors. This design allows large transport trucks to unload commodities on the nonir-
radiated side; the commodities are then loaded onto the conveyor system and trans-
ported through the shielded labyrinth for irradiation. Irradiated products exit into a
separate product section where additional freezer, refrigeration, and docks are pro-
vided.
The facility is almost complete and should be ready for operation by November,
1992. It is located next to the FDACS/DPI caribfly mass rearing facility in Gainesville,
FL.
Recent research with irradiated caribflies includes cooperative studies by FDACS
and the USDA Animal & Plant Health Inspection Service (APHIS) in the LaBelle area
for 3 seasons. The release of approximately 35 million sterile flies produced a population
reduction of up to 99% (Holler and Harris, 1983). Beginning in January, 1991, releases
of sterile caribflies in combination with a parasite, Diachasmimorpha longicaudata
(Ashmead), were initiated by FDACS, USDA, and the University of Florida. In the
first 6 months of 1991 about 40 million sterile caribflies were released on Key Biscayne.
As a part of the parasite rearing program, about 4 million caribfly larvae per week are
being irradiated to prevent the emergence of adults from nonparasitized larvae. The
new irradiation facility will have the capacity to irradiate over 10 million larvae or pupae
per minute. In the future any sterile insect program will not be limited due to lack of
irradiation facilities. All researchers interested in cooperative irradiation studies on the
caribfly are invited to contact the Florida Commodity Irradiation Facility.

REFERENCES CITED

BURDITT, A. K., JR., F. LOPEZ-D., L. F. STEINER, D. L. VON WINDEGUTH, R.
BARANOWSKI, AND M. ANWAR. 1974. Applications of sterilization techniques
to Anastrepha suspense (Loew) in Florida, USA. FAO/IAEA Symposium on the
sterility principle for insect control. IAEA, SM-186, 42: 93-101.
HATTON, T. T., R. H. CUBBEDGE, L. A. RISSE, P. W. HALE, D. H. SPALDING, AND
W. F. REEDER. 1982. Phytotoxicity of gamma irradiation on Florida grapefruit.
Proc. Florida State Hort. Soc. 95: 232-234.
HOLLER, T. C., AND D. L. HARRIS. 1983. Efficacy of sterile releases of Caribbean
fruit fly, Anastrepha suspense, (Diptera: Tephritidae), against wild populations
in urban hosts adjacent to commercial citrus. Florida Entomol. 76: 251-258.
LOPEZ-D., F. 1970. Sterile-male technique for eradication of the Mexican and Caribbean
fruit flies: Review of current status. In Sterile-male technique for control of fruit
flies. IAEA, Vienna. STI 276: 111-117.
SMITTLE, B. J., R. E. BROWN, AND M. E. RHODES. 1991. A new linear facility for
the treatment of agricultural commodities. Nuclear Instruments and Methods in
Physics Research, B56/57: 1229-1231.
VON WINDEGUTH, D. L. 1982. Effects of gamma irradiation on the mortality of the
Caribbean fruit fly in grapefruit. Proc. Florida State Hort. Soc. 95: 235-237.


227










Florida Entomologist 76(2)


CARIBBEAN FRUIT FLY-FREE ZONE CERTIFICATION
PROTOCOL IN FLORIDA (DIPTERA: TEPHRITIDAE)

S. E. SIMPSON
Division of Plant Industry
Florida Department of Agriculture and Consumer Services
Winter Haven, FL 33881

ABSTRACT

The Caribbean Fruit Fly Protocol is a body of regulations under which fresh Florida
citrus fruit may be certified free of Anastrepha suspense (Loew) and shipped to citrus
producing areas of the world. Presently, Japan, Bermuda, and the states of California,
Hawaii, and Texas have accepted this method of certification. The certification is based
on the fruit coming from specific A. suspense controlled areas ("designated areas"). For
the 1990-91 growing season, 8.8 million boxes of citrus were certified fly-free from
groves totalling 114,200 acres.


RESUME

El protocolo de la mosca de las frutas del Caribe es una series de reglamentos bajo
los cuales los frutas de citricos de Florida pueden ser certificados como libres de infes-
taci6n de la mosca de las frutas del Caribe Anastrepha suspense (Loew) y pueden ser
enviados a las areas productoras de citricos. Actualmente, Jap6n, Bermuda y los estados
de California, Hawaii y Texas han aceptado este metodo de certification. La certification
se basa en que la fruta que viene de areas con un control especifico de la mosca del
Caribe ("areas designadas"). Para la cosecha de 1990-1991, se certificaron 8.8 millones
de cajas de citricos como libre de mosca de la frutas, las cuales provenian de huerto
libres de mosca, representando un total de 114,200 acres.





The Caribbean fruit fly (caribfly), Anastrepha suspense (Loew), is a serious pest of
many tropical and subtropical fruits of central and south Florida. Since their 1965 intro-
duction into the Miami area (Weems 1965), to the present, this pest has caused concern
for many Florida growers and consumers throughout the world. Due to the limitation
of available national and international markets and the need to protect other fruit-pro-
ducing areas of the world against this pest, rigid agricultural quarantines have been
established to prevent the movement of contaminated material.
Quarantine treatment procedures utilizing ethylene dibromide fumigation
safeguards required very harsh and expensive post-harvest handling (Riherd 1990).
This added to the market cost and increased the difficulty of marketing treated fruit in
national and international markets. In 1983, the U.S. Environmental Protection Agency
(EPA) cancelled the use of ethylene dibromide (EDB) for domestic regulatory treat-
ments of citrus. Prior to this date, EDB was the approved and accepted treatment
procedure for certifying citrus free of the caribfly. However, the EPA extended the
use through the 1987-88 fruit production season for citrus destined for Japan. Because
of the loss of EDB, alternative treatments were limited to the fumigant methyl bromide
(MB), which damages certain varieties of citrus, and cold storage treatment, which is
costly and time consuming.


228


June, 1993









Caribbean fruit fly '91: Simpson


229


In the early 1980s, studies were conducted to develop alternative measures that
would comply with quarantines established by other citrus-producing areas of the world.
Based upon these initial studies and a better understanding of the caribfly as it relates
to citrus, an acceptable quarantine procedure was established (Riherd 1990). This pro-
cedure is referred to as the "Fly-Free Zone Certification Protocol". Presently, Ber-
muda, Japan, and the states of California, Hawaii, and Texas have accepted the fly-free
quarantine procedure (Japan-U.S. Caribfly Protocol on Fresh Florida Citrus, 1990).
The current procedures for certifying citrus with the fly-free zone concept require
that the fruit come from specific caribfly controlled, or designated areas in 16 citrus-pro-
ducing counties in Florida approved for shipment of fruit.
There are two basic provisions of the fly-free concept: first, the designated area and
a buffer zone must be maintained free of preferred caribfly hosts: loquat, Eriobotrya
japonica (Thumb). Lindl., rose apple, Syzygium jambos (L.) Alst., Cattley quava,
Psidium cattleianum Sabine, common guava, Psidium guajava L., and Surinam
cherry, Eugenia uniflora L. Second, trap surveys must be routinely conducted to
monitor any caribfly movement into the area, the monitoring zone.
Additional provisions emphasize preferred host plant survey and removal, monitor-
ing and inspection of packinghouses shipping certified fruit, and maintaining identity of
certified fruit. Each governmental agency has provisions for acceptance based upon
review or inspection. Currently there are two basic procedures for certifying citrus
from areas maintained free of caribfly. The first procedure is based on negative trap-
ping. The designated area must be located 3 miles (4.8 km) from areas where preferred
host plants are distributed, must be at least 300 acres (120 ha) in size, and must be
surrounded by a 1.5 mile wide (2.4 km) host-free buffer zone (see Table 1).
The second certification procedure is referred to as "bait spray". To qualify for this
procedure, the following requirements must be met: 1) minimum size must be 40 acres
(16 ha) surrounded by a 300-foot (91.2 m) wide buffer zone, 2) buffer zone must be free
of preferred host plants, 3) the designated area must be at least 1/2 mile (0.8 km) from
areas where numerous host plants are present, and 4) application of an aerial bait spray
consisting of a mixture of 2.4 oz. (71.04 ml) 91% malathion and 9.6 oz. (284.2 ml) protein
hydrolysate bait per acre which must be applied at 7 to 10 day intervals beginning 7
days before harvest and continuing until the end of harvest (Table 1).
Additional, and less restrictive, certification criteria have been established for early
season grapefruit which are shipped during August 1 to December 20. These procedures
are based on the resistance of early season citrus fruit to caribfly infestation (Greany
et al. 1983, 1985).
As can be seen in Table 2, the total acreage certified has significantly increased over
the last five years. The 1990-91 citrus fruit season had 114,240 acres certified in 15
eligible citrus producing counties (see Table 3). With the Caribbean Fruit Fly Protocol,
a safe and effective procedure has been established allowing export of citrus fruit to
areas requiring quarantine safeguards. The largest importer of fresh Florida citrus is
Japan. Since the beginning of the 1990-91 shipping season, there have been 11,511,936
4/5 bushel cartons of citrus fruit shipped to Japan; 10,564,673 cartons of white seedless
grapefruit, 619,493 cartons of colored seedless grapefruit, 327,750 cartons of oranges,
and 20 cartons of tangerines (see Table 4). Of this total, 1.6 million 4/5 bushel cartons
were short term cold-treated, 1 million were long term cold-treated, and 8.8 million
cartons were exported using the Caribbean Fruit Fly Protocol. The fly-free certification
method has become an increasingly popular and accepted procedure and represents 52%
of the total Japanese fresh fruit export market over a five-year period (see Table 5).
The Caribbean Fruit Fly Protocol is administered by the Florida Department of
Agriculture and Consumer Services, Division of Plant Industry and United States De-
partment of Agriculture, Animal and Plant Health Inspection Service, Plant Protection










Florida Entomologist 76(2)


June, 1993


TABLE 1. REQUIREMENTS FOR EARLY SEASON AND STANDARD CARIBBEAN FRUIT
FLY-FREE ZONE CERTIFICATION.

Early Season Standard
Certification Certification

Description Negative Bait Negative Bait
Trapping Spray Trapping Spray

Start Date August 1 August 1 August 1 August 1
Ending Date Dec. 20 Dec. 20 End of Season End of Season
Type Fruit Grapefruit Grapefruit Grapefruit Grapefruit
only only and Oranges and Oranges
Distance from
Concentration 3 miles 300 feet 3 miles 0.5 mile
of Hosts
Monitoring 300 feet 300 feet 1.5 mile 300 feet
Distance
Trapping weekly weekly weekly weekly
Bait Sprayed no 10 days no 7-10 days
before prior to
harvest harvest
No. Traps 2/sq. mi. 15/sq.mi. 15 traps/ 15 traps/
5/sq.mi. (min. of 4 sq.mi. sq.mi.
traps)
Size (min.) 300 acres 40 acres 300 acres 40 acres
Buffer size 1.5 miles 300 feet 1.5 mile 0.5 mile
Minimum 7 days 10 days 30 days 30 days
Trapping before before
Period harvest harvest


and Quarantine. Program funding is provided by the citrus industry through grower
assessments. Several citrus marketing economists have recently stated that this
cooperative governmental program for the shipment of fresh Florida citrus using the
fly-free zone concept has been a great success story. Using the fly-free zone concept,
the Florida grower has realized added revenue through this program and the negative
balance of trade has been reduced in excess of 75 million dollars for the 1990-91 season.
To date, caribfly infested fruit has not been detected in shipments of fresh Florida
citrus.

TABLE 2. TOTAL FLORIDA CITRUS ACRES CERTIFIED USING THE CARIBBEAN
FRUIT FLY-FREE ZONE CERTIFICATION METHOD FROM 1986 TO 1991.

Fruit Designated Total Number Number
Season Areas Acres of Counties Acres Certified

1986/87 162 48,600 2 16,500
1987/88 322 96,600 4 32,000
1988/89 744 223,200 7 62,020
1989/90 902 270,600 13 77,300
1990/91 1,095 328,500 15 114,240


230









Caribbean fruit fly '91: Simpson


TABLE 3. FLORIDA COUNTIES CITRUS ACRES CERTIFIED USING THE CARIBBEAN
FRUIT FLY-FREE ZONE CERTIFICATION METHOD, EARLY SEASON, AND
STANDARD DURING THE 1990-91 SEASON.

Early Season Standard
Certification Certification

Bait Negative Bait Negative
County Spray Trapping Spray Trapping Total

Brevard 200 0 0 0 200
Charlotte 0 300 0 300 600
Collier 240 0 560 0 800
DeSoto 80 0 0 0 80
Glades 80 0 240 0 320
Hardee 0 0 0 0 0
Hendry 2,120 1.200 920 1,200 5,440
Highlands 80 300 120 2,400 2,900
Indian River 8,200 14,700 6,120 15,900 44,920
Lee 240 0 160 0 400
Martin 240 0 3,440 0 7,080
Okeechobee 0 600 80 600 2,320
Polk 0 0 160 0 160
St. Lucie 4,480 16,500 4,560 22,200 47,740

Total Acres 20,680 33,600 17,360 42,600 114,240





TABLE 4. MONTHLY 1990-91 JAPANESE EXPORT OF 4/5 BUSHEL BOXES OF FRESH
FLORIDA CITRUS USING DIFFERENT CARIBBEAN FRUIT FLY CERTIFICA-
TION METHODS.

Certification Method

Cold Cold Fly
Treatment Treatment Control
Month Short Term Long Term Zone Total

08/90 -0- -0- 5,670 5,670
09/90 -0- -0- 456,272 456,272
10/90 -0- -0- 584.985 584,985
11/90 -0- -0- 649,008 649,008
12/90 -0- -0- 658,452 679,446
01/91 253,679 20,994 658,452 1,891,850
02/91 330,342 262,602 1,733,642 2,326,586
03/91 399,551 287,513 1,750,425 2,437,489
04/91 350,476 23,521 1,377,550 1,961,547
05/91 292,817 166,883 59,383 529,093

Total 1,626,865 1,071,805 8,813,266 11,511,936












232


June, 1993


Florida Entomologist 76(2)


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Caribbean fruit fly '91: Heath et al.


REFERENCES CITED

GREANY, P. D., S. C. SYTER, P. L. DAVIS, P. E. SHAW, AND D. L. CHAMBERS.
1983. Biochemical resistance of citrus to fruit flies. Demonstration and elucidation
of resistance to the Caribbean fruit fly, Anastrepha suspense. Entomol. Exp.
Appl. 34: 40-50.
GREANY, P. D., P. E. SHAW, P. L. DAVIS, AND T. T. HATTON. 1985. Senescence-re-
lated susceptibility of Marsh grapefruit to laboratory infestation by Anastrepha
suspense (Diptera: Tephritidae). Florida Entomol. 68: 144-150.
RIHERD, C. C. 1990. Citrus production areas maintained free of Caribbean fruit fly for
export certification. Proc. Intl. Fruit Fly Symposium, Antiqua, Guatemala, Oct.
1990. (In press).
WEEMS, H. V., JR. 1965. Anastrepha suspense (Loew) Diptera: Tephritidae. Florida
Dept. Agr. Cons. Serv., Div. Plant Ind., Ent. Circ. No. 38. 4 pp.
















DEVELOPMENT OF ATTRACTANTS FOR
MONITORING CARIBBEAN FRUIT FLIES
(DIPTERA: TEPHRITIDAE)

R. R. HEATH, N. D. EPSKY, P. J. LANDOLT, AND J. SIVINSKI
Insect Attractants, Behavior, and Basic Biology Research Laboratory,
Agricultural Research Service
U.S. Department of Agriculture,
Gainesville, FL 32604

ABSTRACT

Methods for monitoring Caribbean fruit flies, Anastrepha suspense, are reviewed
and areas of essential research required are suggested. Types of attractants discussed
include food, pheromone, visual, and acoustical cues. Additionally, current information
regarding the chemistry of male-produced pheromones and analytical methods for their
detection and elucidation are reported. The predominant monitoring methods used are
either cumbersome to deploy or ineffective. However, attempts to develop improved
traps are often hindered by the lack of an understanding of the underlying fly response.
The linking of currently available analytical techniques with an understanding of A.
suspense behavior should allow optimization of attractants and traps, and provide pow-
erful methods for population monitoring.










234 Florida Entomologist 76(2) June, 1993



RESUME

Se revisan metodos de monitoreo de la mosca del Caribe Anastrepha suspense y se
sugieren areas esenciales para investigaci6n. Los tipos de atrayentes discutidos incluyen
alimentos, feromonas, trampas visuales y acusticas. Adicionalmente se report informa-
ci6n sobre la quimica de feromonas producidas por el macho y los metodos analiticos
para su detecci6n y determinaci6n. Los metodos actuales de monitoreo son impracticos
o poco efectivos. Sinembargo, los esfuerzos de mejoramiento de estas trampas se ven
retrazados por la falta de entendimiento de la respuesta de la mosca. Las tecnicas
analiticas unidas a los conocimientos sobre comportamiento de la mosca del caribe,
facilitarfan unos metodos mas poderosos de monitoreo.




The threat of the Caribbean fruit fly (caribfly), Anastrepha suspense (Loew) (Dip-
tera: Tephritidae), in citrus-growing regions of south Florida is of considerable economic
importance. Even a small infestation of flies makes all fruit grown in the area suspect
and thus unsalable to many potential domestic and foreign markets without costly post-
harvest treatments or establishment of fly-free zones (Riherd 1993, Simpson 1993).
Because of this threat and the potential for introduction of the caribfly into other citrus-
growing states, much emphasis has been placed on detection of this species.
Several approaches have been used to develop detection methods to monitor popula-
tions of pest fruit flies (Economopoulos 1989). The traps currently used for caribflies
are either cumbersome to deploy or ineffective, and research in this area is often ham-
pered by a lack of understanding of the fly attraction behavior. It is beyond the scope
of this article to provide an in-depth review of all systems tested for caribfly detection.
It is, however, germane to the discussion of caribfly attractants to provide a brief
explanatory review of the various attractants. We present in this discourse an overview
of several attraction methods with discussions regarding research pitfalls and oppor-
tunities involved in developing improved lures for caribfly detection.

FOOD ATTRACTANTS

Review

Adult fruit flies require sugar to survive (Christenson & Foote 1960), and honeydew
is recognized as an important food source for adult tephritids (Hagen 1958). Females
also require protein to ensure fecundity, and the protein requirement is the primary
basis for traps for detection of Anastrepha spp. (Anonymous 1989). A number of hydro-
lyzed proteins have been used as baits to attract fruit flies, but comparisons of several
proteins indicated that hydrolyzed torula yeast (HTY) was superior for attracting
caribflies (Lopez et al. 1971, Burditt 1982). Addition of sodium borate (borax) to the
HTY reduced bait decomposition without affecting catch (Lopez & Becerral 1967), and
a pelleted formulation of HTY and borax was developed to facilitate field placement of
baits (Lopez et al. 1968). McPhail traps, bell-shaped glass traps with a water reservoir
(Newell 1936), baited with 5-6 HTY-borax pellets are currently used for monitoring
caribfly populations in Florida (Anonymous 1989). Other baits and/or trap types have
been tested for caribfly detection. Non-baited yellow disks were inferior to HTY-borax-
baited McPhail traps (Witherell 1982), but yellow sticky board traps with ammonium
acetate or 3-phenylpropyl-2-methylpropanoate were as effective as HTY-borax baited









Caribbean fruit fly '91: Heath et al. 235

McPhail traps (Burditt et al. 1983). Davis et al. (1984) compared baited and non-baited
triangular cardboard traps (Jackson traps) to HTY-borax baited McPhail traps. Addi-
tion of bait (cotton wicks soaked in aqueous yeast hydrolysate) to Jackson traps in-
creased capture of females, but not males. However, a greater number of flies and a
higher proportion of immature female flies were caught by the baited McPhail traps.
In studies in a guava grove in Homestead, FL, yeast hydrolysate-baited Jackson traps
and HTY-borax-baited McPhail traps were equally effective when population densities
were high (in the fall), but the baited McPhail traps were superior in the spring when
caribfly population densities were low (Mason and Baranowski 1989).
Bacteria on plant surfaces may serve as a protein source for adult tephritids in
nature (Drew et al. 1983). Addition of actively growing bacteria to protein suspensions
increased attraction of the Queensland fruit fly, Dacus tryoni Froggatt, over protein
suspensions without bacteria (Drew & Lloyd 1989). Bacterial by-products may similarly
attract caribflies. McPhail traps baited with a fermenting mixture of citrus juice and
brown sugar were successfully used to trap caribflies in early studies in Florida (Newell
1936). Davis et al. (1984) speculated that the increased attraction by HTY-borax in
McPhail traps versus aqueous yeast hydrolysate-soaked cotton wicks in Jackson traps
was due to volatiles from breakdown products of the HTY in solution.

Research Opportunities

Although a number of protein-rich materials have been screened for attractant activ-
ity, there is little information on the chemicals responsible for caribfly attraction. Chem-
ical constituents of various protein attractants used for fruit flies have been investigated
(Morton & Bateman 1981, Buttery et al. 1983), but the attractiveness of individual
constituents was not examined. The development of a protocol for interfacing the be-
havioral response with food chemical isolates is necessary to determine the specific
volatiles responsible for caribfly attraction. This should lead to the development of less
cumbersome traps baited with the attractant in a controlled-release formulation. The
results of this research would circumvent difficulties involved in use of currently avail-
able food-based traps.

VISUAL ATTRACTANTS

Review

Fruit flies may use a number of visual cues to locate hosts, and visual cues alone or
in conjunction with chemical cues have been used successfully in developing traps for
fruit flies (Prokopy 1975, Landolt et al. 1988). Greany et al. (1977, 1978) found that
caribflies were strongly attracted to, and could be trapped by fluorescent orange sticky
traps that reflected maximally at 590 nm (Arc Yellow, Day-Glo Color Corp., Cleveland,
Ohio). The trap catch was predominantly female, and most of the trapped females were
sexually mature. Thus, the observed attraction was the result of fruit-seeking rather
than foliage-seeking behavior (Greany et al. 1978). Davis et al. (1984) explored a number
of trap designs and found that Jackson traps with orange stripes captured more
caribflies than solid orange or white traps. Sivinski (1990) found that 20-cm diam. orange
spheres were significantly more effective at catching male caribflies than smaller or
differently colored spheres, but female caribflies were trapped equally on 20-cm green
spheres.










Florida Entomologist 76(2)


Research Opportunities

Caribflies are responsive to visual cues and considerable research has focused on
shapes and colors attractive to caribflies in hopes of developing an effective dry trap
alternative to liquid-baited McPhail traps. However, dry trap use is currently restricted
because of the need for sticky material on the trap surface. In addition, significant
numbers of other insects are attracted to these traps and considerable effort is required
to sort unwanted insects from the captured caribflies. Incorporation of chemical attrac-
tants that attract only caribflies may enhance the utility of these traps if the number
of non-target insects could be reduced. Research related to the development of better
sticky material that could be regenerated in the field is also needed.

ACOUSTICAL ATTRACTANTS

Review

In concert with the release of pheromone vide infra, males produce an audible signal,
i.e. call. Production of male-specific sounds in caribflies was documented by Webb et
al. (1976). Calling males produced a pulsed and audible signal but fell silent as a female
approached. If the female was receptive and made contact with the male, the male
produced a precopulatory song. If the female was unreceptive, the male resumed calling.
Females may use these sounds to assess male size and vigor. Larger males called earlier
in the sexual activity period and their calls had shorter pulse-train intervals (Burk &
Webb 1983). Male calling increased flight activity of virgin but not mature females
(Webb et al. 1983). Attraction of virgin females to male calling sounds has been demon-
strated in field-cage tests. Significantly more females were attracted to tape-recorded
male sounds than to silent control traps (Webb et al. 1983).

Research Opportunities

The general utility of using acoustical attractants at this time is unknown. Methods
for providing these signals in the field at a reasonable cost would be needed. Considering
current technology, however, there may be some future role for caribfly acoustical
attractants.

PHEROMONE ATTRACTANTS

Review

Potentially the most powerful attractant, and seemingly the most difficult to study,
is the male-produced pheromone. Research that began in 1972 and continues to date
has not yet resulted in a pheromone-based trap for the caribfly. Early work described
courtship and mating behavior of caribflies and documented pheromone production by
puffing males (Nation 1972). Female flies were attracted (in laboratory bioassays) to
live males, to whole body extracts of males, and to papers that had been placed in cages
with puffing males. Subsequent studies by Perdomo (1974) showed that both females
and males were attracted to live males, and that male-baited traps caught five to ten
times more flies than food-baited traps in field trials using laboratory-reared, virgin
flies.


June, 1993









Caribbean fruit fly '91: Heath et al. 237

Initial studies on the chemical nature of the pheromone extracted from abdomens of
sexually-mature male caribflies resulted in the identification of (Z)-3-nonenol and (Z,Z)-
3,6-nonadienol (Nation 1975, 1977, 1983). Subsequent investigations of abdominal ex-
tracts of male flies performed by Battiste et al. (1983) resulted in the identification of
two additional components, the lactones, anastrephin (trans-hexahydro-trans-4,7a-di-
methyl-4-vinyl-2-(3H)-benzofuranone) and epi-anastrephin (trans-hexahydro-cis-4,7a-
dimethyl-4-vinyl-2-(3H)-benzofuranone). Laboratory bioassays of these compounds
showed that all were individually attractive to females, but a blend of all four compo-
nents was the most attractive to females (Nation 1975). A synthetic mix of the four
components, however, failed to attract flies in field trials (Nation 1989). A fifth compo-
nent, a macrolide (E,E)-4,8-dimethyl-3,8-decadien-10-olide) was identified and synthe-
sized by Chuman et al. (1988) and has been named suspensolide. Additionally,
P-bisabolene and ocimene have been reported as volatiles emitted by the caribfly (Tum-
linson 1988, Nation 1991, Rocca et al 1992). More recently, E,E-a-farnesene has been
reported (Rocca et al. 1992).
Although significant research efforts have gone into the identification and synthesis
of the putative pheromone chemicals released by male caribflies, one is left with the
question "So what?" Admittedly, the chemistry of the male caribfly pheromone is com-
plex. A typical chromatogram of volatiles collected from "calling" males contains numer-
ous compounds (Figure 1). Analysis of some of the pheromonal components is further
complicated by their thermal liability. For example, the identification of suspensolide
was not completed until 1988 and the identification of E,E-a-farnesene not until 1992.
Elucidation of these components in earlier research was hampered by the lack of appro-
priate analytical methodologies now available to researchers. Careful consideration
must be given to the analyses of compounds such as suspensolide. From studies con-
ducted in our laboratory using synthetic material we have determined two factors that
may result in the loss of suspensolide. A loss of approximately 25% of suspensolide
occurs when Tenax is used as the adsorbent material (Figure 2). More importantly, the
elevated injector temperatures commonly used with split-splitless injectors can result
in an additional loss of approximately 75% of suspensolide (Figure 3). Thus, prior to
1988, the method of collection coupled with method of injection resulted in the inability
to detect suspensolide as a major volatile of the male produced caribfly pheromone.
To illustrate the various aspects of the analytical protocol currently used in our
laboratory for the analyses of male produced pheromone from caribflies, we provide the
following brief review of the methods. Although the analytical methods described are
used for caribfly research, these techniques, which have been developed over a period
of several years, are applicable to identification of other pheromonal systems.

Collection of Volatiles.

A complete description of the system used to in our laboratory to collect volatiles
has been recently published (Heath and Manukian 1992). The system (Figure 4) consists
of three parts: 1) a plastic coupler used to press charcoal filters against the glass flange
of the insect holding chamber, thus purifying inlet air; 2) a glass insect holding chamber
constructed of Pyrex glass with a flange and 50/55 male ground-glass joint outlet; and
3) a multiport collector base. Manual switching for collection of volatiles on one of the
three collector traps or purge is accomplished using a four-way, multiport valve. A
flowmeter controls the amount of air pulled by a vacuum pump through the system. An
aluminum screen, placed upwind of the collector traps in the insect holding section,
keeps the insects upwind of the collectors. Volatiles are collected on traps using Super-










Florida Entomologist 76(2)


250 -


Z ,




I-


0-


5 9 20 30
MINUTES


Fig. 1. Gas chromatogram of pheromonal components collected from male caribflies.
Column used was 50 m x 0.25 mm ID BP-1 (apolar phase).


10




0




-10




-20




-30


zA 8USPEN8OUDE


A ANASTREPHIN


/_ EPI-ANASTREPHIN


Fig. 2. Average percent loss of suspensolide and rearrangement products that occur
with different type of adsorbents used in caribfly pheromone collection (n = 3). Error
bars indicate standard deviation.


June, 1993


238









Caribbean fruit fly '91: Heath et al. 239


C 4

< 20
ILU
C1
z 0
I-
o -20
UJ
-40
CO
O -60
I-
z
w -80

S-100
IL- -100


180 200 230 250 275
INJECTOR TEMPERATURE (C)
ZZ 8 SUSPENSOLIDE / ANASTREPHIN / EPI-ANASTREPHIN
Fig. 3. Average percent loss of suspensolide and rearrangement products that occur
with different injector temperatures when split-splitless injection is used in caribfly
pheromone analyses (n = 3). Error bars indicate standard deviation.

Q (Alltech Assoc. Inc., Deerfield, IL) as the adsorbent and then eluted with methylene
chloride. An internal standard is added for subsequent analyses.

Analysis of Volatiles.

Capillary gas chromatography is conducted using a retention gap column prior to
the analytical capillary column. This system permits the injection of 5-100 pl of solvent
and collected volatiles without concentration and without loss of performance of the
analytical column. A combination of three fused silica columns connected in series using
GlasSeal connectors (Supelco, Inc. Bellefonte, PA) is used. The primary fused silica
column (8 cm x 0.5 mm ID) is connected to the injector and the retention gap column.
This primary column permits the use of 0.4 mm O.D. stainless steel needles with a
septum injector. Selection of retention gap columns for use with the analytical column
is determined by the phase ratio of both columns (Grob 1982; Murphy 1989). For the
purpose of caribfly pheromone analyses, the retention gap columns used are 10m x 0.25
mm ID trimethyl silane deactivated fused silica (Quadrex, New Haven, CT). The analyt-
ical column typically employed for analyses is a 50 m x 0.25 mm ID BP-1 (apolar
phase).
Gas chromatographic analyses are conducted using a Hewlett-Packard Model 5890
gas chromatograph, equipped with a cool-on column capillary injector (septum injector)
which is held at ambient room temperature during injection of the extracted pheromone
sample. Detection of the compounds is performed by a flame ionization detector. Helium
is used as the carrier gas at a linear flow of 18 cm/sec. The following temperature
program is used the column is held isothermal at 600C for 2 min and subsequently
the oven is temperature programmed at 200/min to 1600C. Chromatographic data is
stored and analyzed in a Nelson 4000 data system.


m. ~ ~~ ~~ _m l/ 3_ l -l
/T
, lZI I





-L










Florida Entomologist 76(2)


VACUUM




1 ---
2^' -^


Fig. 4. Illustration of collection system used to collect pheromone emitted by Carib-
bean fruit flies.


Confirmation of known pheromonal compounds and identity of new compounds is
performed using a combination of spectroscopic methods. Initial structure identification
is attempted using mass spectrometry. In our laboratory, a gas chromatograph with a
cool-on column capillary injector is coupled to a Finnigan Ion Trap mass spectrometer.
We obtain both electron impact (EI-ITDMS) and chemical ionization (CI-ITDMS)
spectra of the compounds(s). Typically the reagent gas used for CI-ITDS is isobutane.
Occasionally, when additional information is desired, CI-ITDS is obtained using am-
monia or methane as the reagent gas. Often the identity of new structures require
additional spectroscopic information for their delineation. Infrared spectra of compounds
can be obtained using vapor phase and solution infrared spectra and are obtained in our
laboratory using a Nicolet 20SXC GC-FTIR spectrometer. Samples for vapor phase
spectra are introduced to the FTIR spectrometer via a gas chromatograph equipped
with cool-on column capillary injector. If the structure is still uncertain, proton nuclear
magnetic resonance spectra are obtained ['H] with a Bruker AC300 (Belrica, MA) 300
MHz Fourier transform spectrometer using either CDC1, or C6D6 as the solvent and
tetramethyl silane as an internal reference. Additional information (although somewhat
dated) regarding the spectroscopic methods can be obtained in a review article by Heath
and Tumlinson (1984).

Research Opportunities

Analytical methods for the detection and elucidation of the pheromonal components
of the caribfly are available and have been extensively researched. Although some
bioassay systems have been reported for determining female caribfly response to male-
produced pheromone, there is a general lack of knowledge of the behavior associated
with the response. What is required is a discriminating attraction bioassay that could
be used to provide information relating to relevant response criteria of the pheromonal
components. Subsequent to the development of a rigorous bioassay, the evaluation of
a pheromone-based trapping system for caribfly could be undertaken using synthetic
pheromone compounds which have been formulated to release the chemicals at a rate
and ratio used in nature. Further optimization may provide a powerful attractant for
female caribflies. Such a system would have a significant impact not only for use as a
monitoring tool, but also have potential as a female caribfly annihilation system.


240


June, 1993









Caribbean fruit fly '91: Heath et al.


TRAP EFFICIENCY
Trap efficiency is influenced by fruit fly behavior and reflects the physiological state
of the fly. Food-baited traps tend to catch more females than males due to the greater
food demands of reproductive females as well as the tendency for males to feed in the
territory they are defending (Dodson 1982). On guava, females use immature green
fruit for oviposition and mature pale yellow fruit for feeding (Burk 1983). Thus, female
attraction to green versus orange substrates should reflect physiological condition. Pref-
erential male attraction to orange versus green spheres (Sivinski 1990) may reflect
either food-seeking or mate-seeking behavior. Dodson (1982) found that laboratory-
reared females spent more time on fruit, either engaged in feeding or oviposition activ-
ity, while males spent little time on fruit and obtained most of their food from the leaf
surface. In contrast, Burk (1983) observed wild flies, and frequently found males on
fruit, either feeding or courting females. When not on fruit, males spent most of their
time on leaves either defending territory from other males or advertising for females
(Dodson 1982).
Traps combining several attractant cues have had mixed success. Painting all or part
of an HTY-borax-baited McPhail trap orange color failed to increase catch (Burditt
1982). Male-baited 20-cm diam orange spheres, however, caught significantly more
males and females than food-baited spheres or McPhail traps (Sivinski 1990). The com-
bination of sound and pheromone (whole body extract) did not increase catch over
pheromone alone, and traps with sound and/or pheromone were not as attractive as
traps with live males (Webb et al. 1983).
Calkins et al. (1984) determined the probability of detecting various populations of
caribflies with HTY-borax-baited McPhail traps. Recovery rates were low, with 11-15%
of flies recovered from field-released populations of 90-999 laboratory-reared flies per
0.4 ha. They projected that > 33 traps per 0.4 ha were needed to detect low populations
of 9 flies per 0.4 ha (detection probability = 90%). Fewer traps, however, were needed
to detect or monitor higher populations. An intense trapping program, used to delineate
new fruit fly infestations, places 80-40-20-10-5 traps per square mile in a grid covering
81 square miles (Anonymous 1989). Monitoring known populations requires a lower
density of 5-10 traps per square mile (C. O. Calkins, personal communication).

Research Opportunities

It is apparent from the review of food-based attractants that a greater understanding
of the physiology of the caribfly as it relates to attraction to various cues would facilitate
the use of such attractants. Further research is needed to understand the relationships
that exist between nutrients needed by adult flies and the volatile cues produced from
natural sources. This should lead to development of efficient trapping systems to capture
flies attracted to these lures.


SUMMARY

The success in developing better attractants for the caribfly may require significant
changes in the directions that are currently being used to achieve this goal. Considerable
effort must be placed in obtaining a better interface between the understanding of the
biology of the insect and the attractiveness of the semiochemical being investigated.
Continued isolation and identification of chemicals at a rapid pace without determining
their potential usefulness in the field will most likely provide only marginal improvement










242 Florida Entomologist 76(2) June, 1993

in caribfly attractants. An integrated approach in which the insect response to the
semiochemical is demonstrated and understood should provide a significant series of
excellent lures for detection and perhaps even control of caribflies.

ACKNOWLEDGEMENTS

We wish to thank A. Manukian and B. Dueben for technical assistance and discus-
sions.



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DAVIS, J. C., H. R. AGEE, AND D. L. CHAMBERS. 1984. Trap features that promote
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279-284.
DREW, R. A. I., AND A. C. LLOYD. 1989. Bacteria associated with fruit flies and their
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DODSON, G. 1982. Mating and territoriality in wild Anastrepha suspense (Diptera:
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June, 1993









Caribbean fruit fly '91: Baranowski et al.


BIOLOGICAL CONTROL OF THE CARIBBEAN FRUIT FLY
(DIPTERA: TEPHRITIDAE)

RICHARD BARANOWSKI', HOLLY GLENN1, AND JOHN SIVINSKI2
'University of Florida
Tropical Research and Education Center
Institute of Food and Agricultural Science
University of Florida
Homestead, FL 33031

2Insect Attractants, Behavior, and Basic Biology Research Laboratory,
Agricultural Research Service
U.S. Department of Agriculture,
Gainesville, Florida 32604

ABSTRACT

Parasitic Hymenoptera were introduced into Florida in an attempt to bring the
Caribbean fruit fly (caribfly) under biological control. A total of 15 species of parasites
from 4 families were imported. Twelve species were released, 9 have been recovered
in the field, and 5 are considered established. These coexist with both endemic fruit fly
parasites and generalist species, which serendipitously attack caribfly. Inundative re-
leases of the braconid Diachasmimorpha longicaudata (Ashmead) to control caribfly
are presently being tested by USDA/ARS, the University of Florida, and the Florida
Division of Plant Industry. It is hypothesized that releases of parasites will augment
numbers of natural enemies during periods when wasps are relatively uncommon due
to difficulties in host finding. The lower numbers of flies that may result could be
important in creating and maintaining fly-free zones. A renewed interest in the biolog-
ical control of fruit flies promises future explorations for new natural enemies and novel
means of employing them.

RESUME

Especies de hymenopteros parasiticos fueron introducidos en Florida con el fin de
mantener la mosca del Caribe bajo control biol6gico. Se importaron un total de 15
species de parAsitos los cuales pertenecian a 4 families. Estos coexisten con los
parAsitos endemicos y species generalistas, las cuales atacan la mosca del Caribe.
Liberaciones masivas de el braconido Diachasmimorpha longicaudata (Ashmead) estan
siendo realizadas por el USDA/ARS, la Universidad de Florida y la Florida Division of
Plant Industry. La hipotesis es que las liberaciones de parasites aumentarAn los
ndmeros de enemigos naturales durante periods en que las avispas son poco comunes
dada la cantidad menor de hospederos. Las pocas moscas que se encuentren pueden ser
importantes en el mantenimiento de zonas libres de moscas. El interns renovado del
control de la mosca de la fruta promete que se realizaran mas exploraciones de enemigos
naturales y nuevos metodos seran tambien utilizados.




The Caribbean fruit fly (caribfly), Anastrepha suspense (Loew), has been introduced
and established in Florida on at least two occasions. It was first reported from Florida


245










246 Florida Entomologist 76(2) June, 1993

based on adults collected at Key West in 1931. In early 1932, a quarantine was set up
to prohibit the removal of host fruits from Key West and adjacent islands, and in 1933
an eradication campaign was initiated by the Florida Department of Agriculture, Divi-
sion of Plant Industry (formerly the State Plant Board). This campaign ended in 1936
when it was decided that eradication was not practical because A. suspense had also
been found on the upper Keys and on the mainland. Apparently the population could
not sustain itself as no additional specimens were collected between 1936 and 1959 when
two adults were trapped at Key West. No further finds were noted until April 23, 1965,
when larvae were found in Surinam cherries (Eugenia uniflora L.) in Miami Springs.
Four days later, adults were trapped in the same area, and by the end of June,
thousands had been trapped. Since 1965, A. suspense has spread into 30 counties
throughout the southern and central portions of Florida, extending as far north on the
east coast as St. Johns County and on the west to Hernando County. More than 90
kinds of fruit have been recorded as hosts, those preferred being guava (Psidium
guajava L.), peach (Prunus persicae Batsch), Surnam cherry, tropical almond (Ter-
minalia catappa L.), and loquat (Eriobotrya japonica Lindl). Other fruits that are
attacked include mango (Mangifera indica L.) and grapefruit (Citrus X paradisi) as
well as other kinds of citrus (Norrbom 1988).
Early investigations showed that several species of hymenopterous parasitoids were
already using the caribfly as a host, although the number parasitized was low. Those
already present were Spalangia cameroni Perk., S. endius Walker, Pachycrepoideus
vindemiae (Rond) (Pteromalidae), a Cothonaspis species (Eucoilidae), and a Trichopria
species (Diapriidae). These parasitoids are not specific and attack other kinds of flies
such as house flies. In addition, two braconid parasitoids Bracanastrepha (=Opius)
anastrephae (Vier.) and Doryctobracon anastrephilum (Marsh) were recovered. Both
of these parasitoids are specific to fruit fly larvae and undoubtedly existed in Florida
as parasitoids of another species of fruit fly Anastrepha interrupta Stone which is only
known to attack the fruit of an uncommon native plant Schoepfia chrysophylloides (A.
Rich.).
Since fewer than 1% of Caribbean fruit fly pupae that were collected were
parasitized, it was decided to introduce additional species of parasitoids in an attempt
to reduce Caribbean Fruit fly populations (see Table 1). Introductions began late in 1967
with the cooperation of several scientists and agencies: Dr. F. D. Bennett, Common-
wealth Institute of Biological Control, Trinidad; Drs. L. Steiner, T. T. Wong, D. L.
Chambers, USDA Pacific Basin Area Tropical Fruit and Vegetable Research Labora-
tory, Hawaii; Mr. Robert Rhode, Organismo International Regional de Sanidad Ag-
ropecuaria (OIRSA), Costa Rica; Ings. D. L. Arrieta, Elezer Jimenez Jimenez, Direc-
cion General de Sanidad Vegetal, Mexico, and Dr. R. Pralavorio (INRA), Antibes,
France.
The first parasitoid released was Doryctobracon areolatus (Szepligeti) obtained from
the Commonwealth Institute of Biological Control, Trinidad. The original stock con-
sisted of 7 males and 17 females. It was carried through six to seven generations in the
laboratory and in July, 1969, 45 males and 26 females were released. From fruit samples
taken one week after the initial release, 578 A. suspense pupae were recovered, 22 of
which were parasitized by D. aureolatus showing that the laboratory reared wasps
were successful in seeking out infested fruit. Recoveries were made through September,
1969, with levels of parasitization ranging from 3.4% to 43%, averaging 13%. Parasitiza-
tion rates during July and August. of the following year averaged 49%. D. aureolatus
populations have declined in the southern portion of the caribflies' range, apparently
because of competition with other parasites. It remains abundant to the north in the
Lake Okeechobee area (Sivinski, Calkins, Baranowski, unpublished data).











Caribbean fruit fly '91: Baranowski et al.


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248 Florida Entomologist 76(2) June, 1993

Diachasmimorpha (=Biosteres) longicaudatus (Ash.), obtained from Mexico and
Hawaii, was established in the laboratory in 1972. Laboratory studies indicated that
this species was more successful than D. aureolatus in searching for and parasitizing
larvae of A. suspense. It was released at the Tropical Research and Education Center
during November, 1972, and monitoring of fruit samples after the release indicated that
it was established. Because this species easily became established with the release of
only 20 to 30 individuals at a site, it was decided to disseminate it as widely as possible
within the caribfly range. A novel approach was used. With the cooperation of the IFAS
Extension Service, newspaper, radio and TV coverage, and support from Chapters of
the Rare Fruit Council, Inc., "brown bags" of parasitoids were distributed to homeown-
ers having infested fruit in their yards. Within the distribution period, several thousand
homeowners picked up parasites to release in their yards. In the five year period after
these releases in 21 counties, annual adult caribfly catches averaged about 40% lower
than during the years before the parasitoid releases (trapping records of the USDA/
Plant Protection & Quarantine, and the Florida Department of Agriculture and Con-
sumer Services, Division of Plant Industry).
In addition to D. aureolatus and B. longicaudatus, several other parasitoids have
been studied in the laboratory, and some released. Biosteres arisanus (Sonan) (= Bios-
teres oophilus) is a parasitoid that attacks the egg of certain fruit fly species in Hawaii.
Several thousand individuals were released in cooperation with Dr. P. Greany, USDA
Insect Attractants, and Basic Biology Research Laboratory, Gainesville, Florida, dur-
ing 1974 and 1975, but B. arisanus did not become established. Opius bellus, a larval
parasitoid of Anastrepha species was introduced in small numbers from Trinidad, but
it was not colonized in the laboratory and was not field released. Dirhinus giffardii
Silvestri, a pupal parasitoid, Psyttalia concolor (Silvestri) and Trybliographa daci
Weld, larval parasitoids, were obtained from the Institut National de la Recherche
Agronomique (INRA) laboratory in France during 1977-1979. Each species was col-
onized in the laboratory using A. suspense as a host, and 30-90 thousand of each were
released in the field during the same period. Both T. daci and P. concolor have been
recovered in small numbers, which indicates that they are established, but at very low
numbers. D. giffardii has not been recovered in the field.
More recently, we have introduced Doryctobracon trinidadensis (Gahan), a large
species from Trinidad that also attacks Anastrepha larvae. It has been successfully
colonized in the laboratory and small-scale field releases were made during the summer
and fall of 1985. Limited recoveries were made after releases, but it is not considered
established.
Biosteres (=Opius) vandenboschi (Fullaway), Psytallia incisi (Silvestri) and
Diachasmimorpha tryoni (Cameron), all larval parasitoids, also have been'recently
introduced from Hawaii. B. vandenboschi and D. tryoni were successfully colonized in
the laboratory on caribfly larvae. All three were released in limited numbers, and all
have been recovered in small numbers.
Even with the establishment of this battery of "biological weapons", the caribfly
remains abundant and a serious pest. In fact, the classical biological control of any fruit
fly to levels below economic threshold is often considered difficult or unfeasible (Debussy
1989, Wharton 1989). There are several generalizations that perpetuate this impression.
(1) Most tephritids of economic importance can be found, at least periodically, in rela-
tively large fruit. Fly larvae may safely live inside these larger fruits where their
parasites' ovipositors cannot reach. For example, parasitism of the apple maggot,
Rhagoletis pomonella (Walsh), by the opiine braconid Biosteres melleus (Gahan) is
greater in hawthorn (Crataegus sp.) than in apple, presumably because of the latter's
greater size (Porter 1928). In a similar instance, larvae of the olive fly, Dacus oleae,
are sheltered in large host fruit from attack by Psyttalis (-Opius) concolor (Manikas &








Caribbean fruit fly '91: Baranowski et al.


Tsiroyannis 1982). However, in a year-long survey of 6 fruit species, a fruit's size was
only weakly correlated to caribfly parasitism by Diachasmimorpha longicaudata
(Sivinski 1991). This may be due to the parasite's extensive foraging over fallen fruit,
which could allow it to attack larvae as they leave even the largest fruit to pupate, and
a propensity for mature larvae to feed relatively close to the surface of many fruits. (2)
Host discrimination (avoidance by foraging females of fruit previously marked by
ovipositing parasites, Lawrence et al. 1978) may restrict the number of parasites pro-
duced per fruit. There is little evidence as yet that host discrimination by D. long-
icaudata plays an important role in restricting fly mortality in the field (JS & RB unpub.
data). This may be due to the weaker response of female D. longicaudata to host-mark-
ing pheromones deposited after oviposition when parasites are at high density levels
(Lawrence et al. 1978, JS & RB unpub. data). As host markers age, the reaction of
parasites to them changes. After 5 days in the laboratory, such markers actually become
attractive (JS & RB unpub. data). (3) There are pronounced time lags between the
growth of host and parasite populations. For example, peak parasitism of the Mediter-
ranean fruit fly (Ceratitis capitata (Wied.)) occurs after the fly has reached high levels
(Wong et al. 1984). Regular seasonal fluctuations in fruit give fruit flies frequent oppor-
tunities to escape their natural enemies. (4) Fruit flies have greater fecundity and
dispersal abilities than their parasites, so that even high parasitism levels (>90%) of a
first generation of flies are insufficient to prevent the growth of a host population
(Debussy 1989). (5) Finally, the economic threshold for control is very high for cultural
and quarantine reasons. Fruit in the United States is often considered spoiled if a single
maggot is present. The substantial reduction of caribfly larvae in guava from a mean
of 50 to a mean of 5 is still of little commercial interest, although such a degree of control
might be of practical importance in areas where fruit is grown for local consumption
and is traditionally eaten flies and all, as in guava paste.
These arguments should not discourage biological control programs. There are cer-
tain conditions under which fruit fly natural enemies have been useful to American
agriculture (Baranowski 1987; Bess & Haramoto 1958; T. Wong et al. 1991). A particu-
larly favorable set of circumstances may presently exist for biological attack on the
caribfly. The first positive factor is the low infestation rates in grapefruit, the host of
principle economic importance in Florida. The second is the increasing application of
the "fly-free zone" concept, where an absence of trapped flies captured during certain
periods allows a grapefruit grower to export his crop without postharvest treatment on
the presumption that the fruit are not infested. It has been suggested that fly-free zones
could be created and maintained by simple suppression of fly numbers with parasites.
This could be accomplished by increasing fly mortality in preferred hosts such as
Surinam cherry, loquat, guava and tropical almond, which in turn might reduce the
migration of flies into adjacent citrus. Lower migration, in theory, could result from
there being both fewer flies to disperse as well as less motivation for the remaining flies
to leave preferred hosts when competition for ovipositional sites is low. It was noted,
for instance, that the host range of the Oriental fruit fly, Bactrocera (Dacus) dorsalis,
shrank after the introduction of parasites into Hawaii (Bess & Haramoto 1958).
A major biological barrier to suppression, the lag between fly and parasite population
growth, could be overcome by the establishment of new parasites that forage more
effectively at low host densities or by inundative release of presently established para-
sites while fly numbers are at cyclical low points. Inundative releases ofD. longicaudata
and combinations of sterile male flies and parasites are presently being cooperatively
tested by the USDA/ARS, University of Florida and Florida Division of Plant Industry.
It should be noted that parasite mass releases have 2 potential advantages over sterile
male releases. First, the parasites do not scar fruit as might happen when female flies
are released along with sterile males. Second, there is no potential for the error, confu-


249









Florida Entomologist 76(2)


sion, and delay that growers in fly-free areas might face when their traps capture flies
which then must be examined and determined to be part of a sterile release.
Should inundatively released parasites prove to be a useful control for the caribfly,
another barrier to their use still exists, the expense of production. This may be miti-
gated by the ability to separate laboratory-reared male and female fruit fly larvae by
their different development rates. Female caribfly larvae develop more quickly than
males and can be segregated when they leave the rearing medium to pupate (Sivinski
& Calkins 1990). A perennial problem in fruit fly rearing facilities that provide insects
for sterile releases is large numbers of unwanted females. These females are not thought
to contribute significantly to the sterile control but do consume half the resources of
the rearing program. If female caribfly larvae could be set aside as parasite hosts, what
had been an expensive liability to a control program, could become an asset.
Most of the parasites released in Florida were originally obtained during explora-
tions of the old world tropics soon after the second world war. The search at the time
was for natural enemies of Bactrocera species. These parasites proved to have a broad
host range that included Anastrepha spp. There is a growing interest within the USDA/
ARS and universities for initiating a new generation of explorations, this time in Latin
America. It is hoped that new parasites with specialized abilities may be found preying
upon the 185 species of Anastrepha living in the American tropics. Parasites that attack
the shallowly placed eggs of the caribfly or that have unusually long ovipositors, or that
forage effectively at low host densities, would all be welcome candidates for classical or
augmented releases.

REFERENCES CITED

BARANOWSKI, R. 1987. Caribbean fruit fly feels sting of biocontrol. Univ. of Florida
Research 87: 12-13.
BESS, H. A., AND F. H. HARAMOTO. 1958. Biological control of the oriental fruit fly
in Hawaii. Proc. Tenth Intern. Cong. Entomol. 4: 835-840.
DEBOUZIE, D. 1989. Biotic mortality factors in tephritid populations, p. 221-227 in A.
S. Robinson and G. Hooper [eds.], Fruit flies: their biology, natural enemies and
control. Elsevier, Amsterdam.
LAWRENCE, P. 0., P. D. GREANY, J. L. NATION, AND R. M. BARANOWSKI. 1978.
Oviposition behavior of Biosteres longicaudatus, a parasite of the Caribbean
fruit fly, Anastrepha suspense. Ann. Entomol. Soc. Am. 71: 253-256.
MANIKAS, G., AND V. TSIROYANNIS. 1982. Biological control ofDacus oleae in Greece
using the parasite Opius concolor Szepl. Etal d'advancement des travaux et
exchange d'information sur les problems poses par la lutte integre en oleiculture.
Comm. Commun. Europe. INRA, Paris, pp. 105-113.
NORRBOM, A. L., AND K. C. KIM. 1988. A list of reported host plants of the species
of Anastrepha (Diptera: Tephritidae). USDA APHIS publication 81.
PORTER, B. A. 1928. The apple maggot. U. S. Dept. of Agriculture Technical Bulletin
66: 1-48.
SIVINSKI, J. M. 1991. The influence of host fruit morphology on parasitism in the
Caribbean fruit fly (Anastrepha suspense). Entomophaga 36: 447 454.
SIVINSKI, J. M., AND C. O. CALKINS. 1990. Sexually dimorphic developmental rates
in the Caribbean fruit fly (Diptera: Tephritidae). Environ. Entomol. 19: 1491-
1495.
WHARTON, R. 1989. Classical biological control of fruit infesting Tephritidae, p. 303-313
In A. S. Robinson and G. Hooper [eds.]. Fruit flies: their biology, natural
enemies, and control. Elsevier, Amsterdam.
WONG, T. T. Y., N. MOCHEZUKI, AND J. S. NISHIMOTO. 1984. Seasonal abundance of


June, 1993









Caribbean fruit fly '91: Holler & Harris


parasitoids of the Mediterranean and Oriental fruit flies (Diptera: Tephritidae)
in the Kula area of Maui, Hawaii. Environ. Entomol. 13: 140-145.
WONG, T. T. Y., M. M. RAMADAN, D. O. MCINNIS, N. MOCHIGUKI, J. I.
NISHIMOTOM AND J. C. HERR. 1991. Augmentative releases of Diachas-
mimorpha tryoni (Hymenoptera: Braconidae) to suppress a Mediterranean fruit
fly (Diptera: Tephritidae) population in Kula, Maui, Hawaii. Biol. Control. 1: 2-7.









EFFICACY OF STERILE RELEASES OF CARIBBEAN FRUIT
FLIES (DIPTERA: TEPHRITIDAE) AGAINST WILD
POPULATIONS IN URBAN HOSTS ADJACENT TO
COMMERCIAL CITRUS

T. C. HOLLER' AND D. L. HARRIS2
1USDA, APHIS, Science & Technology
Caribbean Fruit Fly Station
P.O. Box 147100
Gainesville, FL 32614-7100

2Florida Department of Agriculture & Consumer Services
Division of Plant Industry
P.O. Box 147100
Gainesville, FL 32614-7100

ABSTRACT

The sterile male release technique was tested either as an alternative to fumigation
or as a supplement to a fly-free management program in 1988 for control of the Carib-
bean fruit fly, Anastrepha suspense (Loew). The test area consisted of 19-28 sq.
kilometers with a corresponding non-sterile fly release area. Releases began in January,
1988, and continued generally through June 1990. Efficacy was measured by determin-
ing the presence or absence of flies using an aggressive trapping program. Suppression
of wild A. suspense in the first year could not be measured easily but, by the end of
the third year, measurable reduction was evident.

RESUME

La tecnica de machos esteriles fue probada como una alternative a la fumigaci6n o
como un suplemento a el program de manejo de zonas libres de moscas para el control
de la mosca de la fruta del Caribe, Anastrepha suspense (Loew). El area experimental
consisti6 de 19-28 kilometros cuadrados. Las liberaciones comenzaron en Enero, 1988 y
continuaron hasta Junio 1990. Se midi6 la eficacia de las liberaciones por medio de un
trampeo intensive. La supresi6n de A. suspense no pudo ser media facilmente durante
el primer afio, pero al final del tercer afio, la reducci6n fue evidence.









Florida Entomologist 76(2)


June, 1993


Citrus from various counties in south Florida is quarantined against the Caribbean
fruit fly (caribfly), Anastrepha suspense (Loew), by the states of Arizona, California,
Hawaii and Texas. Additionally, some foreign countries regulate the entry of Florida
citrus. Approximately 0.93 to 8.8 million boxes of Florida grapefruit have been shipped
to Japan each year since 1988. The potential exists for 11 million boxes by the end of
the 1991-92 production season.
Prior to 1984, fumigation with ethylene dibromide (EDB) was the approved regulat-
ory treatment for certifying Florida citrus free of the caribfly. EDB treated fruit was
routinely shipped to foreign and domestic markets. Export problems arose after the
U.S. Environmental Protection Agency issued a notice of intent to cancel registrations
of pesticides containing EDB for post harvest fumigation of citrus (Anonymous 1983).
Since 1984, EDB treatments of citrus for domestic consumption have been rescinded,
but the U.S. Environmental Protection Agency extended its use on citrus destined for
Japan through the 1987-88 fruit production season (Anonymous 1984).
Because of the loss of EDB, treatment alternatives for citrus fruit are limited to the
use of the fumigant methyl bromide, which damages certain varieties of citrus, and cold
storage, which is costly and time consuming. Presently, under a bilateral agreement
with the Ministry of Agriculture, Forestry & Fisheries, Japan has approved shipment
of citrus from designated counties in Florida. Guidelines under which grapefruit and
oranges from production areas can be certified are stated in the Japan-US Caribfly
Protocol on fresh Florida fruit.
As an alternative to fumigation and to supplement the fly-free management pro-
gram, inundative releases of sterile caribflies was proposed. The use of the Sterile
Insect Technique (SIT) to eradicate insect pests has been well documented (Burditt et
al. 1974, Cheikh et al. 1975, Knipling 1960, Steiner et al. 1962, Rhode et al. 1971).
Therefore, the Florida Department of Agriculture & Consumer Services, Division of
Plant Industry (DPI), in cooperation with USDA-APHIS-S&T, conducted a three-year
pilot release project between 1988-90 in an urban area of southwest Florida. The objec-
tive of the test was to measure the efficacy of sterile fly releases as they relate to
suppression of wild populations in high host density residential areas adjacent to com-
mercial citrus groves.



MATERIAL AND METHODS

Tests were conducted during a three year period: January through August, 1988;
February through June, 1989; and September 1989 thru May 1990. Procedures de-
veloped to test the feasibility of utilizing sterile Mexican fruit flies, Anastrepha ludens
(Loew), as a "regulatory treatment" for citrus in south Texas were generally adapted
for this study (Holler et al. 1984).
The La Belle area of Hendry county, an isolated urban area in southwest Florida,
was selected for the test. The sterile fly release area was selected based on host distri-
bution/density/caribfly population surveys. The area varied year to year from 19 to 28
square kilometers (7.6-11.2 sq miles) of residential neighborhoods with a corresponding
non-release area. Primary hosts occurring in numbers were loquat (Eriobotryajaponica
Lindl), surinam cherry (Eugenia uniflora L.), and common guava (Psidium guajava
L.) (Swanson & Baranowski 1972). Cattley guava (Psidium cattleianum Sabine),
calamondin (Citrus mitis Blanco), and kumquat (Fortunella crassifolia Swingle) were
less abundant.









Caribbean fruit fly '91: Holler & Harris


Prior to the initiation of trapping for the SIT project, the La Belle urban area was
trapped for approximately a one-year period (October 1986-87). A total of 26 traps were
serviced on a 10-day, 2-week schedule. Caribfly buildup began in March and decreased
by September with highly significant numbers of flies being trapped in May. With
caribfly population densities determined as adequate to meet test objectives, and realiz-
ing that the release of sterile flies in this area was more acceptable to the citrus industry
than releases of steriles in counties participating in the fly-free protocol program, tests
were initiated with trap placement beginning the first week of January 1988.
Caribfly pupae were produced at the Florida Department of Agriculture Caribbean
Fruit Fly Mass-Rearing Facility in Gainesville (Minno and Holler 1991). Twelve-day-old
pupae were irradiated with a 7 krad dosage from cobalt-60 at the USDA-ARS
laboratories in Gainesville, packaged in plastic bags at the mass rearing facility, and
sent in cooled shipping containers to the release site by a commercial carrier. Upon
arrival, pupae were removed and portioned into six number-12 paper bags and set in
the eclosion units (20-25,000 per unit). The eclosion unit was derived from a plastic tote
box 23.5 x 19.5 x 13 in (60 x 50 x 33 cm) by cutting a section 11.5 x 14 in (29 x 37 cm)
out of the top and a section 4.5 x 10.5 in (11 x 27 cm) out of each side. A 22-mesh
stainless steel screen was welded into the openings. Pupae were either rolled in a
Day-GloR fire-orange fluorescent pigment using a clear plastic bag and then placed in
the paper bags, or placed in bags under vermiculite which had been mixed with the
pigment previously. Prior to adult eclosion, sugar and protein (cubes) and water (agar
block) were placed on the top screened portion of the lid. The completed units were
transferred to a 60 x 12 ft (18 x 3.6 m) laboratory trailer and held at 24-270C for one
week.
Sterile flies were released weekly. Releases were conducted in the early hours of
daylight to avoid excessive fly mortality during transportation and release from the
eclosion units. Contents of the eclosion units were distributed by a person seated on a
chair mounted in a truck-bed as the truck moved through the release area. The number
of sterile flies released per week over a designated area varied from 150,000 to
3,250,000, according to laboratory production availability.
Following the initial trap/host surveys, an aggressive adult trapping program was
implemented to monitor the wild population to determine the effect of sterile flies
released during the test period. Clear glass McPhail traps with five torula yeast-borax
tablets in 500 ml of water were used to monitor sterile/wild fly ratios (Burditt 1982).
Traps were placed in trees consistent with procedures specified in the DPI Fruit Fly
Survey Manual. All servicing of traps was conducted by DPI personnel. Sixteen traps,
dependent upon host availability, were located per square mile in both the release and
non-release test areas.
McPhail traps were checked weekly. Initial determination of the status of the trap-
ped flies, either wild or sterile, was made at the field station. The fly was determined
to be sterile if the fluorescent dye on the ptilinum was evident when observed under a
blacklight. If little or no evidence of dye appeared in the ptilinum, flies were sent to
the DPI laboratory in Gainesville where the ptilinum was extracted and checked for the
presence of dye. If no dye was present, the specimen was dissected to observe the
reproductive system for possible radiation damage.
Reduction of the wild caribfly population was determined by comparing the change
in the population in the non-release area with the corresponding change in the wild
population in the release area (Weidhaas et al. 1974). The formula used to measure the
changes was as follows: 100 [(100xRC)/(RBxOI)], where RC = release area density in
current month; RB = release area density in baseline month; OI = observed increase
or decrease in non-release areas from baseline month through the current month, where
a stable population OI is 1.0 (0% increase or decrease).


253










Florida Entomologist 76(2)


RESULTS AND CONCLUSIONS

The reduction of the Caribbean fruit fly in the urban area, as measured by trapping
for the three test periods, is illustrated in Tables 1-3 and Figures 1-3. Overall, as
sterile-to-wild fly ratios improved from test period to test period, the caribfly popula-
tions decreased substantially. Results for the period of January 1988 through May 1990
are summarized as three individual periods: January thru August, 1988; February thru
June, 1989; and September 1989 thru May 1990.


TABLE 1. RELEASE, RECOVERY, AND STERILE-TO-WILD RATIO OF CARIBBEAN
FRUIT FLIES IN LA BELLE, FLORIDA, 1988.

Number of Flies % Ratio Trapped:
1988 Released (Million) Recovery Sterile-to-Wild

JAN 0.39 0.09 N/A
FEB 0.84 0.18 118
MAR 0.81 0.39 286
APR 0.39 1.00 48
MAY 0.79 0.15 17
JUN 0.15 0.74 27



TABLE 2. RELEASE, RECOVERY, AND STERILE-TO-WILD RATIO OF CARIBBEAN
FRUIT FLIES IN LA BELLE, FLORIDA, 1989.

Number of Flies % Ratio Trapped:
1989 Released (Million) Recovery Sterile-to-Wild

FEB 1.25 0.11 18
MAR 1.25 0.24 172
APR 2.26 0.15 524
MAY 1.53 0.08 234
JUN 2.26 0.07 1,327



TABLE 3. RELEASE, RECOVERY, AND STERILE-TO-WILD RATIO OF CARIBBEAN
FRUIT FLIES IN LA BELLE, FLORIDA, SEPTEMBER 1989-MAY 1990.

Number of Flies % Ratio Trapped:
1989-1990 Released (Million) Recovery Sterile-to-Wild

SEP 2.82 0.02 N/A
OCT 1.38 0.40 185
NOV 1.84 0.12 580
DEC 2.18 0.12 542
JAN 1.97 0.27 2,334
FEB 1.50 0.29 1,117
MAR 3.64 0.12 2,725
APR 3.25 0.36 1,893
MAY 3.26 0.20 680


254


June, 1993










Caribbean fruit fly '91: Holler & Harris


255


Fig. 1. Mean monthly wild fly trap catches in release and non-release area, La Belle,
Florida, 1988.

January-August 1988 Releases

Initially in 1988, sterile-to-wild fly ratios (100:1 expected) for February and March
exceeded the ratio required and some suppression of the wild population was evident


5


0.4

C3






01


O ,
FEB MAR APR MAY JUN



Fig. 2. Mean monthly wild fly trap catches in release and non-release areas, La Belle,
Florida, 1989.


5


04
t-




0o 2




0
Fo


MAR APR MAY JUN JUL AUG









256


Florida Entomologist 76(2)


Fig. 3. Mean monthly wild fly trap catches in release
Belle, Florida, 1989-90.


June, 1993


and non-release areas, La


by the end of March (56%). From April through June, the sterile-to-wild ratio dropped
below the target threshold of 100:1. Finally, the non-release population was reduced by
a combination of high temperatures, lack of oviposition hosts, and reduced adult food
sources, thus making comparisons impossible.

February-June, 1989 Releases

The sterile-to-wild fly ratio in March 1989 almost doubled (172:1) the expected level
and this ratio generally improved steadily throughout the test period (February through
June). When the population in the control area soared in April, the population in the
treated area had declined. The estimated monthly suppression from March through
June was 52, 95, 98.5 and 99.6% respectively.

September, 1989-May, 1990 Releases

During December 1989, the two areas (treated and control) experienced a severe
freeze which reduced host availability and wild fly densities. However, by March 1990,
the wild population had recovered to measurable levels and was increasing in the non-re-
lease area at the end of May. The sterile-to-wild fly ratio during this period significantly
exceeded 100:1 in the release area. The estimated suppression in the release area for
April and May was 76% and 78%, respectively.
Fly quality, sex ratio, mating competitiveness and the number of flies released
weekly varied significantly throughout the three test periods. Host densities and distri-
bution varied as modifications in size of the release/non-release areas occurred between
test periods. The impact of these factors, individually or as a whole, may have directly
impacted the level of reduction in the wild population from month to month during each
test period and/or between the three tests.










Caribbean fruit fly '91: Holler & Harris


Despite these factors, the results suggest that inundative releases of sterile flies can
be effective in reducing wild populations of caribfly under these conditions. These re-
sults compare favorably with the apparent high degree of control of wild populations of
the Mexican fruit fly in urban, rural, and commercial citrus using SIT in the Lower Rio
Grande Valley of Texas (Holler et al. 1984). Whether or not this reduction in an urban
area directly reduces population pressures on adjacent commercial groves remains to
be investigated. Potentially, the release of sterile caribflies in commercial citrus groves
in conjunction with a fly-free management program could supplement present regulat-
ory requirements. The use of sterile males with parasites of the caribfly could as well
play an important role in wild fly suppression. Long range objectives could incorporate
area wide/state wide suppression/eradication of wild populations which ultimately would
open tropical fruit markets other than for just citrus.

ACKNOWLEDGMENTS

The authors would like to thank Ms. Gina Posey and Dr. Carrol Calkins, USDA-
ARS, Insect Attractants, Behavior and Basic Biology Laboratory, Gainesville, Florida,
for the tabular and graphic presentation of data. Data base preparation and sterile
release impact statements were provided by Dr. David A. Dame, Consultant, Division
of Plant Industry.

LITERATURE CITED

ANONYMOUS. 1983. Environmental Protection Agency Federal Register 48:46234-
46243.
ANONYMOUS. 1984. Environmental Protection Agency Federal Register 49:14182-
14186.
BURDITT, A. K. JR., F. LOPEZ-D., L. F. STEINER, D. L. VON WINDEGUTH, R.
BARANOWSKI AND M. ANWAR. 1974. Application of sterilization techniques to
Anastrepha suspense (Loew) in Florida, USA. Sterility Principles for Insect
Control. IAEA-SM-186/4Z, pp. 93-101.
BURDITT, A. K., JR. 1982. Anastrepha suspense (Loew) (Diptera: Tephritidae) McPhail
traps for survey and detection. Florida Entomol. 65: 367-373.
CHEIKH, M., J. F. HOWELL, E. J. HARRIS, H. BEN-SALAH AND F. SORIA. 1975.
Suppression of the Mediterranean fruit fly in Tunisia with released sterile insects.
J. Econ. Entomol. 68: 237-243.
HOLLER, T. C., J. L. DAVIDSON, A. SUAREZ AND R. GARCIA. 1984. Release of sterile
Mexican fruit flies for control of feral populations in the Rio Grande Valley of
Texas and Mexico. J. Rio Grande Hort. Soc. 37: 113-122.
KNIPLING, E. F. 1960. The eradication of the screwworm fly. Sci. Am. 203: 54-61.
MINNO, M. C., AND T. C. HOLLER. 1991. Procedures Manual for Mass-Rearing the
Caribbean Fruit Fly Anastrepha suspense (Loew) (Diptera: Tephritidae).
Florida Dept. Agriculture & Consumer Services, Division of Plant Industry.
RHODE, R. H., J. SIMON, A. PERDOMO, J. GUTIERREZ, C. F. DOWLING, JR., AND
D. A. LINDQUIST. 1971. Application of the sterile insect release technique in
Mediterranean fruit fly suppression. J. Econ. Entomol. 64: 708-713.
STEINER, L. F., W. C. MITCHELL AND A. H. BAUMHOVER. 1962. Progress of the
fruit fly control by irradiation sterilization in Hawaii and Marianas Islands. Int.
J. Appl. Radiat. Isot. 13: 427-434.
SWANSON, R. W., AND R. M. BARANOWSKI. 1972. Host range of the Caribbean fruit
fly, Anastrepha suspense (Diptera: Tephritidae) in south Florida. Proc. Fla.
State Hort. Soc. 85: 271-274.


257









Florida Entomologist 76(2)


June, 1993


WEIDHAAS, D. E., S. G. BREELAND, C. S. LOFGREN, D. A. DAME, AND P. KAISER.
1974. Release of chemosterilized males for the control of Anopheles albimanus
in El Salvador. IV. Dynamics of the test population. Am. J. Trop. Med. Hyg.
23: 298-308.




eL e e- e- eC e- e e- e--




MANIPULATING AND ENHANCING CITRUS FRUIT
RESISTANCE TO THE CARIBBEAN FRUIT FLY
(DIPTERA: TEPHRITIDAE)

P. D. GREANY' AND J. P. SHAPIRO2
'Insect Attractants, Behavior, and Basic
Biology Research Laboratory
Agricultural Research Service
U.S. Department of Agriculture
Gainesville, FL 32604

2U.S. Horticulture Research Laboratory
USDA, ARS
Orlando, FL 32803

ABSTRACT

The natural resistance of citrus fruit to attack by the Caribbean fruit fly (caribfly)
varies according to fruit senescence and cultivar. Lemons are virtually immune, oranges
are highly resistant, and grapefruit are initially somewhat resistant, at least before
becoming senescent. A method allowing an extension of the innate early-season resist-
ance of grapefruit to fruit flies is described. Elucidation of lemon immunity factors is
needed so that the responsible factors can be incorporated into less resistant cultivars,
perhaps through use of genetic engineering techniques. By extending and/or increasing
resistance of grapefruit, it may be possible to achieve adequate prevention of caribfly
infestation throughout most of the season without the need to use expensive and trouble-
some postharvest disinfestation treatments in order to ship the fruit to quarantine-sen-
sitive states and countries.

RESUME

La resistencia natural de las frutas de citricos al ataque de la mosca de la fruta del
caribe (Caribfly) varia de acuerdo a la edad de la fruta y a el tipo de cultivar. Los
limones son practicamente immunes, las naranjas son muy resistentes, las toronjas son
mas resistentes al ser recien cosechadas, pero luego se veuelven menos resistentes. Se
describe un metodo para alargar el period de resistencia a la mosca en estas toronjas
recien cosechadas. Se necesita identificar los factors que confieren imunidad a el lim6n,
para asi incorporar estos factors en los cultivares poco resistentes, talvez mediante el
uso de ingenieria gen6tica. Al extender o al incrementar la resistencia a la toronja,
puede ser possible el alcanzar una prevenci6n contra la infestaci6n de la mosca de la fruta


258










Caribbean fruit fly '91: Greany & Shapiro


a lo largo de todo el period de cosecha, lo cual disminuiria la necesidad de los tratamien-
tos postcosecha, y ayudaria a facilitar el envio de fruta a paises o estados con reglamen-
tos cuarentenarios para este problema.




Many changes have occurred in the procedures used to assure the absence of the
Caribbean fruit fly (caribfly), Anastrepha suspense (Loew), from Florida grapefuit
since the 1984 Environmental Protection Agency ban on use of ethylene dibromide
(EDB) for postharvest fumigation (Greany & Riherd 1993). Formerly, most grapefruit
destined for shipment to Japan, California, Arizona, and Texas were disinfested after
harvest; now, the emphasis is instead on developing biorational, cost-effective methods
to prevent field infestation of grapefruit by the caribfly. A variety of methods are being
employed to reduce the likelihood of infestation, including removal of alternate host
plants, use of malathion bait sprays, and reliance on early season resistance of grapefruit
to attack (Simpson 1993).
We believe it may be possible to take further advantage of the inherent resistance
of citrus fruit to caribfly attack early in the season (Greany 1989, Greany et al. 1983,
1985) by delaying fruit senescence. Ultimately, by identifying factors in lemons that
confer immunity to fruit flies (Greany 1993), it might be possible to incorporate these
into other less resistant cultivars through plant breeding or by genetic engineering.

EXTENDING EARLY SEASON RESISTANCE

One possibility for manipulation of fruit fly susceptibility is to use the naturally-
occurring plant growth regulator gibberellic acid (GA3) to extend the early season resist-
ance routinely exhibited by grapefruit. Research has shown that GA3 can serve as a
"status quo" hormone, delaying senescence of citrus fruit peel. The traditional use of
GA3 is to allow treated fruit to be kept longer after harvest without suffering the usual
amount of postharvest decay (Coggins 1973, Ali Dinar et al. 1976, Ferguson et al. 1982,
Lima & Davies 1984, McDonald et al. 1987, El-Otmani & Coggins 1991). Subsequent
research has shown that GA3 treatment also reduces susceptibility of citrus fruit to fruit
flies (Greany et al. 1987, McDonald et al. 1988, R6ssler & Greany 1990, Greany et al.
1991). To achieve this, citrus growers must treat the fruit while still on the tree and
still externally green (i.e., prior to "colorbreak"). This causes the fruit peel to remain
green and tough, but it does not interfere with internal fruit ripening. If desired,
treated fruit can be "degreened" prior to sale by use of another natural plant hormone,
ethylene, which causes the chlorophyll to be broken down, revealing the orange or
yellow color normally associated with ripe oranges or grapefruit (McDonald et al. 1987).
In nearly 30 years of use (Coggins & Lewis 1965), no harm to humans has ever been
found due to exogenous application of GA3 to citrus fruit to delay senescence and prolong
the harvest season. Studies of metabolism of GA3 in the fruit revealed that GA3 is
absorbed as, and remains primarily in, the applied form (Ferguson et al. 1986).
Our goal is to use GA3 treatments to reduce the need to use conventional insecticides
to assure the absence of caribfly from grapefruit. Because of increasing concern for the
environment, there is a possibility that malathion bait sprays may be banned, as was
the use of EDB fumigation in 1984. This could jeopardize the annual shipment of $100-
200 million worth of grapefruit from Florida to Japan, California, Arizona, and Texas
where the caribfly could pose a threat if introduced and established (Riherd 1993,
Greany & Riherd 1993, Simpson 1993). Postharvest treatments based on chilling or
heating are available or are being developed (Sharp 1993, McDonald et al. 1993), but


259









Florida Entomologist 76(2)


are not preferred by growers and shippers as compared to field control strategies.
Methyl bromide fumigation is routinely used as a postharvest treatment of citrus fruit
being shipped to California, Arizona and Texas, but its continued use is threatened due
to concern for its potential harm to the ozone layer.
By using GA3, it may be possible to delay application of malathion bait sprays.
Research has shown that GA3-treated fruit are less attractive to caribfly and are less
susceptible even if attacked (Greany et al. 1987). Results of field studies in Florida in
1991 and 1992 showed an 80% reduction of caribfly attack on grapefruit as a result of
GA3 treatment (Greany et al. unpub. data). In addition to protecting the fruit, use of
GA3 treatments instead of conventional insecticides should protect natural enemies
important to biological control of other citrus pests such as scale insects (Rdssler &
Greany 1990).
Our current research is intended to prove the efficacy of GAs treatments in the field
and to reduce the cost of the GAs treatments through optimization of treatment timing
and formulation of the active agent and the associated surfactant needed to facilitate
penetration of the hormone into the fruit peel. In addition, we are developing quantita-
tive indices of fruit fly susceptibility upon which objective judgements could be made
whether to allow shipment of grapefruit without postharvest treatment. In this regard,
we have correlated fruit susceptibility with 4 senescence features: peel color, resistance
to puncture, oil content, and limonin content (Greany et al. in preparation, Shaw et al.
1991, Wilson et al. 1990). Finally, we are evaluating the relative susceptibility of GAs-
treated vs. untreated grapefruit to harm associated with the use of postharvest hot air
treatments (McDonald et al. 1993). Preliminary studies by R. McDonald and Wm. Miller
(USDA ARS, Orlando, FL, unpub. data) suggest that GA3-treated grapefruit are less
easily damaged by heat treatment.


GENETIC TRANSFER OF RESISTANCE FACTORS

A more enduring (and more distant) approach to the control of tephritids would be
to mobilize natural resistance of closely related plants through either conventional
breeding or genetic engineering. The latter possibility is rapidly approaching fruition
through advances in tissue culture and molecular biology. Besides advances in these
areas, however, genetic engineering requires fundamental knowledge of the biochemis-
try behind resistance mechanisms. Since mechanisms involving more than a single pri-
mary gene product (i.e. the enzyme directly responsible for resistance, or responsible
for synthesis of a compound which confers resistance) are presently too complex to
consider, we are searching for sources of single-gene resistance.
A potential source of single-gene resistance in lemons and limes has been suggested
to us (T. Waiss, USDA ARS, Albany, CA, pers. comm.). These fruits have demon-
strated a virtual immunity to attack by the caribfly (Nguyen & Fraser, 1989, Hennessey
et al. 1991). This resistance in lemons and limes strongly correlates with content of a
specific flavonoid, the flavanone eriodictyol, and its glycosides eriocitrin and neoeriocit-
rin (Horowitz & Gentili, 1960, Albach and Redman 1969, Kamiya et al. 1979). Further-
more, eriodictyol itself has shown strong growth inhibition toward Heliocoverpa zea,
while its precursor, naringenin (present in peel of most citrus fruits), showed no activity
(Elliger et al. 1980). If the same holds true for the caribfly, we may have a unique
opportunity to genetically engineer natural resistance into citrus through transfer of a
single gene.
Flavonoids undergo numerous metabolic conversions, many of them enzymatically
mediated by cytochrome P-450 monooxygenases found in the endoplasmic reticulum
microsomess) of plant cells (Heller & Forkmann 1988). The advantages of P-450-
mediated single-step hydroxylation of naringenin to eriodictyol are apparent. Only one


260


June, 1993










Caribbean fruit fly '91: Greany & Shapiro


enzyme is involved, and that enzyme, microsomal flavanone 3'-hydroxylase, has been
prepared and characterized from several plant species (Heller & Forkmann 1988). All
described citrus cultivars contain appreciable pools of naringenin and one of its
glycosides, naringen. Recently, we demonstrated naringenin hydroxylase activity in
undifferentiated callus tissue from oranges (JS, T. Burke, & R. Mayer, USDA ARS,
Orlando, FL, unpub. data). Further characterization of the enzyme, especially by isola-
tion, partial amino acid sequencing, and immunochemical comparison with other plant
cytochrome P-450s, will allow us to identify and isolate the gene that codes for it. The
close phylogenetic relationships of citrus cultivars within the Rutaceae may enhance the
probability of successful genetic transfer, gene expression, and enzymatic activity.

CONCLUSIONS

Clearly, the future of crop plant development lies in our ability to alter selected
physiological and biochemical characteristics of a crop. Since the advent of agricultural
biotechnology, whether we attempt to produce a plant with improved defense
mechanisms, enhanced food quality, or increased productivity, our capabilities are lim-
ited only by the depth of our understanding of underlying physiological mechanisms.
We have presented a brief overview of two distinct and progressive approaches to
increasing the defenses of citrus fruit against tephritid fruit flies, one near term, the
other long term. Both approaches derive from an increased understanding of physiolo-
gical processes in the fruit and their influence on fruit fly attack and development.
Continuing emphasis on gaining and applying basic knowledge should enable ever more
targeted and successful instances of biorational pest management through host plant
resistance.

REFERENCES CITED

ALBACH, R. F., AND G. H. REDMAN. 1969. Composition and inheritance of flavanones
in citrus fruit. Phytochem. 8: 127-143.
ALI DINAR, H. M., A. H. KREZDORN, AND A. J. ROSE. 1976. Extending the grapefruit
harvest season with growth regulators. Proc. Florida State Hort. Soc. 89: 4-6.
COGGINS, C. W., JR. 1973. Use of growth regulators to delay maturity and prolong
shelf life of Citrus. Acta. Hort. 34: 469-472.
COGGINS, C. W., JR., AND L. N. LEWIS. 1965. Some physical properties of the navel
orange rind as related to ripening and to gibberellic acid treatments. Proc. Am.
Soc. Hort. Sci. 86: 272-279.
EL-OTMANI, M., AND C. W. COGGINS, JR. 1991. Growth regulator effects on retention
of quality of stored citrus fruits. Scientia Horticulturae 45: 261-272.
ELLIGER, C. A., B. C. CHAN, AND A. C. WAISS, JR. 1980. Flavonoids as larval growth
inhibitors. Naturwissenschaften 67: 338-339.
FERGUSON, L., M. A. ISMAIL, F. S. DAVIES, AND T. A. WHEATON. 1982. Pre- and
postharvest gibberellic acid and 2,4-dichloro-phenoxyacetic acid applications for
increasing storage life of grapefruit. Proc. Florida State Hort. Soc. 95: 242-245.
FERGUSON, L., T. A. WHEATON, F. S. DAVIES, AND M. A. ISMAIL. 1986. 4C-Gib-
berellic acid uptake, translocation, persistence, and metabolism in grapefruit. J.
Amer. Soc. Hort. Sci. 111: 926-932.
GREANY, P. D. 1989. Host plant resistance to tephritids: an underexploited control
strategy, pp. 353-362 in World Crop Pests: Fruit Flies-Biology, Natural
Enemies and Control, A. S. Robinson & G.H.S. Hooper [eds.]. Elsevier, Amster-
dam.
GREANY, P. D. 1993. Elucidating the biochemical bases for host plant selection and










262 Florida Entomologist 76(2) June, 1993


manipulating resistance to tephritids, pp. 339-340 in Fruit Flies: Biology and
Management, M. Aluja & P. Liedo, [eds.]. Springer-Verlag, New York.
GREANY, P. D., S. C. STYER, P. L. DAVIS, P. E. SHAW, AND D. L. CHAMBERS.
1983. Biochemical resistance of citrus to fruit flies. Demonstration and elucidation
of resistance to the Caribbean fruit fly, Anastrepha suspense. Entomol. exp. &
appl. 34: 40-50.
GREANY, P. D., P. E. SHAW, P. L. DAVIS, AND T. T. HATTON. 1985. Senescence-re-
lated susceptibility of Marsh grapefruit to laboratory infestation by Anastrepha
suspense (Diptera: Tephritidae). Florida Entomol. 68: 144-150.
GREANY, P. D., R. E. MCDONALD, P. E. SHAW, W. J. SCHROEDER, D. F. HOWARD,
T. T. HATTON, P. L. DAVIS, AND G. K. RASMUSSEN. 1987. Use of gibberellic
acid to reduce grapefruit susceptibility to attack by the Caribbean fruit fly Anas-
trepha suspense (Diptera: Tephritidae). Trop. Sci. 27: 261-270.
GREANY, P. D., MCDONALD, R. E., SCHROEDER, W. J., AND P. E. SHAW. 1991.
Improvement in the efficacy of gibberellic acid treatments in reducing susceptibil-
ity of grapefruit to attack by the Caribbean fruit fly, Anastrepha suspense.
Florida Entomol. 74: 570-578.
GREANY, P. D., AND C. RIHERD. 1993. Caribbean fruit fly status, economic impor-
tance, and control. Florida Entomol. 76: 209-211.
HELLER, W., AND G. FORKMANN. 1988. Biosynthesis, pp. 399-425 in The flavonoids:
advances in research since 1980, J. B. Harborne [ed.]. Chapman & Hall, New
York.
HENNESSEY, M. K., R. M. BARANOWSKI, ANDJ. L. SHARP. 1992. Absence of natural
infestation of Caribbean fruit fly (Diptera: Tephritidae) in commercial Florida
'Tahiti' lime fruits. J. Econ. Entomol. 85: 1843-1845.
HOROWITZ, R. M. 1961. The citrus flavonoids, pp. 343-372 in The Orange, its
Biochemistry and Physiology. W. B. Sinclair [ed.]. Univ. Calif. Press, Berkeley.
KAMIYA, S., S. ESAKI, AND F. KONISHI. 1979. Flavonoids in citrus hybrids. Agric.
Biol. Chem. 43: 1529-1536.
LIMA, J. E. 0., AND F. S. DAVIES. 1984. Growth regulators, fruit drop, yield, and
quality of navel orange in Florida. J. Amer. Soc. Hort. Sci. 109: 81-84.
MCDONALD, R. E., P. E. SHAW, P. D. GREANY, T. T. HATTON, AND C. W. WILSON.
1987. Effect of gibberellic acid on certain physical and chemical properties of
grapefruit. Trop. Sci. 27: 17-22.
MCDONALD, R. E., P. D. GREANY, P. E. SHAW, W. J. SCHROEDER, T. T. HATTON,
AND C. W. WILSON. 1988. Use of gibberellic acid for Caribbean fruit fly (Anas-
trepha suspense) control in grapefruit, pp. 37-43 in R. Goren & K. Mendel [eds.],
Proc. Sixth Intl. Citrus Congr., Tel Aviv, Margraf Sci. Books, Weiker-sheim.
MCDONALD, R. E., W. R. MILLER, AND E. J. MITCHAM. 1993. Temperature as a
quarantine treatment and its effect on product condition and quality. Florida
Entomol. 76: 218-224.
NGUYEN, R., AND S. FRASER. 1989. Lack of suitability of commercial limes and lemons
as hosts of Anastrepha suspense (Diptera: Tephritidae). Florida Entomol. 72:
718-720.
RIHERD, C. 1993. Citrus production areas maintained free of Caribbean fruit fly for
export certification, pp. 407-413 in Fruit Flies: Biology and Management, M.
Aluja & P. Liedo, [eds.]. Springer-Verlag, New York.
ROSSLER, Y., AND P. D. GREANY. 1990. Enhancement of citrus resistance to the
Mediterranean fruit fly. Entomol. exp. & appl. 54: 89-96.
SHARP, J. L. 1993. Temperature management quarantine treatments for postharvest
disinfestation of fruit and plant pests including the Caribbean fruit fly (Diptera:
Tephritidae). Florida Entomol. 76:212-218.









Caribbean fruit fly '91: Calkins


263


SHAW, P. E., CALKINS, C. 0., MCDONALD, R. E., GREANY, P. D., WEBB, J. C.,
NISPEROS-CARRIEDO, M. 0., AND S. M. BARROS. 1991. Limonin and naringin
level variations in grapefruit albedo with maturity. Phytochemistry 30: 3215-
3219.
SIMPSON, S. E. 1993. Development of the Caribbean fruit fly-free zone certification
protocol in Florida. Florida Entomol. 76: 228-233.
WILSON, C. W., III, P. E. SHAW, R. E. MCDONALD, P. D. GREANY, AND H.
YOKOYAMA. 1990. Effect of gibberellic acid and 2-(3,4- dichlorophenoxy)
triethylamine on nootkatone in grapefruit peel oil and total peel oil content. J.
Ag. Food Chem. 1990: 656-659.







FUTURE DIRECTIONS IN CONTROL OF THE CARIBBEAN
FRUIT FLY (DIPTERA: TEPHRITIDAE)

C. O. CALKINS
Insect Attractants, Behavior, and Basic Biology
Research Laboratory, Agricultural Research Service
U.S. Department of Agriculture, Gainesville, FL 32604

ABSTRACT

The Caribbean fruit fly (caribfly), Anastrepha suspense, was introduced into Florida
in 1965 and has spread throughout the southern portion of the state, infesting species
of tropical and subtropical fruits. Although it does not present a threat to citrus produc-
tion, it has become a quarantine pest of citrus fruits. Several novel methods of control
are presented that fall under the 3 categories: detection, exclusion, and control/eradica-
tion. Research directed toward better lures and traps are underway. Exclusivity is
being addressed by making the fruit unattractive for oviposition or by adding antibiotic
factors to the host fruit. The concept of the fly-free zone is supported by control/eradi-
cation technology. Bait sprays that contain malathion may be phased out in the future.
Replacement for this and other chemicals must be considered for future control and in
support of the sterile male release method.

RESUME

La mosca de la fruta del Caribe (Caribfly), fue introducida en Florida en 1965 y se
ha expandido en la porci6n sur del estado infestando species de frutas tropicales y
subtropicales. Aunque no represent una amenaza a la producci6n de citricos, se ha
convertido en una plaga cuarentenaria de citricos. Los metodos de control se pueden
agrupar en tres categories: detecci6n, exclusion y control/erradicaci6n. La investigation
dirigida hacia mejores atrayentes y trampas se esta realizando. Se efectua exclusion al
hacer esta fruta menos atractiva para oviposici6n o al agregar antibiotics a la fruta
hospedera. El concept de una zona libre de moscas se basa en una tecnologia de control/
erradicaci6n. Las asperciones con cebos que contengan malathion pueden dejar de
utilizarse en un future. El reemplazo de estos y otros quimicos puede ser considerado
para un control future y en favor del uso de liberaciones de machos esteriles.









264 Florida Entomologist 76(2) June, 1993




The Agricultural Research Service (ARS) launched a detailed National Action Plan
for fruit fly research in San Francisco, CA during the summer of 1991. This plan was
developed in cooperation with fruit growers and shippers, local, state, other federal
agencies and university scientists. It took into consideration the needs expressed by
these cooperators. The primary aim of this program is to provide the necessary re-
search, through a cohesive team effort, that will lead to environmentally and publicly
acceptable, safe technologies for a) detection and delimitation, b) exclusion, c) control
and eradication, and d) fundamental biology. These problems concern species that are
residents or potential threats to the United States. This includes the Caribbean fruit
fly (caribfly), Anastrepha suspense (Loew).
ARS is a problem solving organization dedicated to serving the needs of action and
regulatory agencies and the agricultural industry. Future control opportunities are
divided into 3 areas: detection, exclusion and control/eradication.
Future directions in control technology usually refers to results that are expected
from ongoing or planned research; that is, things that are in the pipeline or that appear
to be feasible. In this paper, I focus on problems identified by the workshop mentioned
above involving the caribfly and projects that are planned or underway at those ARS
laboratories that work directly on this species in Florida. These ARS laboratories are
the Insect Attractants, Behavior and Basic Biology Research Laboratory in Gainesville,
the U. S. Horticultural Research Laboratory in Orlando, the Subtropical Horticulture
Research Laboratory in Miami and the Quality Improvement in Citrus and Subtropical
Products Laboratory in Winter Haven. I don't presume to speak for other agencies that
may be working on these and similar problems.

DETECTION

One of the most frequently mentioned needs for caribfly control in the workshop is
a better trap and lure, preferably a dry trap. The McPhail trap is a glass-invaginated
globe with a liquid reservoir. Flies enter the trap through an opening in the bottom and
drown in the solution. The liquid is composed of a food bait, usually torula yeast or
yeast hydrolyzate, and water (Anonymous 1986). It is the best trap available for detect-
ing all Anastrepha species. Until a better trap is produced, it is the basis for comparison
for all new models. Although new lures that have been proposed for use in the trap,
the basic design has remained the same. Some of the disadvantages of the McPhail trap
are that the specimens are retained in liquid, and in hot weather they decay. In the
process, the fluorescent pigment marker used to identify sterile flies is sometimes lost,
and the specimens are often so badly decomposed that dissections to verify sterility are
not feasible. The trap is very difficult to service and several unwanted species may be
included. The traps are relatively expensive and fragile, and they are frequently broken
or vandalized.
Several studies are under way in Gainesville to produce an efficient trap without the
liquid component. A radical design combined with a new lure that can be easily dis-
pensed will be required. Landolt et al. (1988) reported that the papaya fruit fly trap
must have the attractant and visual cues combined in the trap in order to catch flies.
Sivinski (1990) has noted that visual cues are extremely important factors in the use of
a dry trap. The food baits that are being investigated are the components of torula
yeast, Nu-lure (a derivative of molasses), bird feces, etc. If the attractive component
can be isolated and identified, it, or closely associated chemicals, can be synthesized
and formulated to increase the attractiveness, prolong the activity of the compounds,
and make them easier to handle.










Caribbean fruit fly '91: Calkins


The major components of the pheromone of A. suspense have been identified and
most have been synthesized (Chuman et al. 1988, Nation 1975). These components must
now be tested in various arrays to determine the most effective mixture. This will be
combined with the proper visual cues to produce a trap that, hopefully, will be more
efficient than the McPhail trap and will attract flies from a greater distance.

EXCLUSION

Commodity treatments have been the backbone of quarantine programs. These
treatments have received much attention recently due to the withdrawal of ethylene
dibromide (EDB) by the Environmental Protection Agency (EPA). However, most of
the commodity treatments, such as hot water dips, hot air and vapor heat, are well
known and are only being recertified for major commodities and adapted to new tropical
fruits. What was once a an area of research, is now technology that is being fine-tuned
for various fruit types. One must be careful that improvement of technology is not
identified as research so that resources are not redirected away from discovering new
technology.
If a major breakthrough in exclusion is to be achieved, in terms of exclusion, we
must think of attacking the cause of the problem and not restrict ourselves to addressing
the technology that treats the symptoms. These methods would include the elimination
of the insect or the exclusion of the insect from the fruit. One way this is being addressed
is by development of fly-free zones in areas where widespread eradication of the pest
is not feasible (Anonymous 1990). The Florida Department of Agriculture, Division of
Plant Industry (FDACS-DPI) has been the leader in this program. The fly-free zone
concept consists of maintaining localized fruit growing areas free of caribflies to allow
shipment of fruit from these areas without quarantine treatment. Bait sprays and detec-
tion trapping, developed for control and eradication of fruit flies, have been applied to
this problem to develop a protocol that has now been accepted by Japan, California,
Arizona, Texas and Bermuda. The concept is being adopted by several countries that
may ship fruit to the U.S. These are Ecuador, Brazil, Belize, Spain, Israel and Au-
stralia.
Another way of addressing the problem is to make the fruit unattractive or resistant
to ovipositing females. The use of a known plant hormone, gibberellic acid applied to
the fruit on the tree at the appropriate time, causes the peel of citrus fruit to remain
in an immature state while the interior of the fruit matures normally (Greany et al.
1991). This immature appearing peel inhibits flies from laying eggs in the treated fruit.
Of the few eggs that are inserted, many are killed by substances in the oil glands prior
to or soon after hatch (Greany et al. 1983, Styer and Greany 1983). The first proposal
for the use of gibberellic acid was not well received by the citrus industry. They per-
ceived it as an added expense to production with insufficient benefit. However, as the
fly-free zone concept developed, Japan agreed that immature grapefruit picked before
December 20 is immune from fly attack and those fruits could be shipped without
certification or treatment. When it was explained that this so-called "immune window"
might be widened by the use of gibberellic acid, the industry saw the value for its future
use.
An important spinoff of this work is the renewed interest in developing citrus vari-
eties resistant to attack from fruit flies. There are now tools available to incorporate
desired traits into acceptable varieties in a short time. Genetic engineering is the tool
that can make rapid changes feasible in perennial fruit crop plants. Physiologists and
biochemists may now search for chemicals or enzymes that are responsible for certain
fruits being non-hosts of fruit flies, such as in the case of lemons and limes. The genes
responsible for this resistance could be isolated and inserted into fruit hosts. Dr. Jeffrey


265









Florida Entomologist 76(2)


Shapiro, ARS, Orlando, is interested in isolating certain flavonoids that have insect
antibiotic properties. If the genes responsible can be inserted into the genome of the
target citrus variety, it could result in a variety that is immune to fruit fly attack.
The possibility of enhancing or inserting genes for the enzyme, chitinase, in certain
citrus varieties would create another type of antibiosis and could become a reality. Dr.
Richard Mayer, USDA, ARS, Orlando, FL, is investigating a type of enzyme that
attacks chitin, the building block of fungi, the cuticle of the insect exoskeleton and the
peritrophic membrane in the fore and hind gut of insects. Ingestion of food containing
this enzyme could result in the death of fly larvae.
The limonin content is found in high concentrations in the albedo (the white portion
of the peel) of grapefruit. Levels of this chemical decrease, by an order of magnitude,
during the maturation stage of the fruit. At the same time, these fruits become suscep-
tible to fruit fly attack (Calkins and Webb 1988, Shaw et al. 1991). There are strong
indications that these events are related. This phenomenon has provided the incentive
to determine if limonin is actually a feeding inhibitor. If this is true, and the limonin
content of the peel could remain high during maturation without changing the normal
ripening process of the pulp, either through plant breeding or genetic engineering, the
fruit might remain resistant to attack by fruit flies throughout most of the fruiting
season.
In conclusion, the fly-free zones allows shipment of untreated fruit during the mean-
time. However, a more permanent form of exclusion would be to change a susceptible
fruit into that which is either resistant or immune to fruit fly attack.


CONTROL/ERADICATION

Bait sprays containing malathion are a part of the protocol of fly-free zones and are
also used extensively when exotic fruit flies, such as the Mediterranean fruit fly (medfly)
Ceratitis capitata, invade the state. There are strong indications that malathion concen-
trations in bait sprays could be reduced to 10% of the present recommended dose
without affecting the toxic effectiveness. Larger droplet is the key (J. R. Brazzel,
USDA APHIS, Mission, TX, pers. commun.). This would cause less damage to non-
target organisms and would significantly reduce residues in run-off areas. Replacement
of malathion in bait sprays is of high priority on the list of research needs of both
industry and regulatory agencies because of the environmental and political concerns
posed by its use. There is a possibility that registration of this chemical for this use
may be withdrawn in the near future. Therefore, a search for other agents to kill
feeding adult flies is a high priority of ARS.
Entomogenous nematodes have been known to kill A. suspense adults when confined
in petri dishes (Beavers and Calkins 1984). However, when the nematodes are incorpo-
rated into a bait, the flies are able to imbibe the solution without ingesting the
nematodes. Dr. James Lindegren, USDA, ARS, Fresno, CA, (pers. commun.) has been
able to freeze-dry nematodes and feed them in a bait solution to medflies successfully.
Dr. William Schroeder, ARS Orlando and I are cooperating with Dr. Lindgren in a
project to adapt this technique for use against the Caribbean fruit fly.
The cost of eradicating the caribfly from Florida would be prohibitively expensive
and it would be unfeasible at this time. If the program was initiated, the eradication
efforts would probably begin in the northern part of the fly's range after a particularly
cold winter and proceed southward to the Keys. This program would have to be con-
ducted from start to finish in one year because quarantine boundaries could not be
maintained easily for more than one year because of the difficulty in preventing infested
fruit from being carried northward. This program could cost at least $400 million. This
estimate is based on the cost of the medfly eradication program in California in 1981-


June, 1993


266










Caribbean fruit fly '91: Calkins 267

1982. The fly also exists in the Bahamas Islands, and, because of the large amount of
traffic from there to Florida, the fly would have to be eliminated there first if the State
were to be protected from reinvasion. Under these circumstances, Floridians and the
fruit industry will have to either live with the pest or control it to the point that it does
not interfere with production or marketing. This can be done, but new or improved
methods of control must be employed against it.
The sterile insect technique (SIT) is used extensively against invading species of
fruit flies in California and would be useful here as well. It was used against caribfly in
a limited study in La Belle by FDACS-DPI in 1989 and 1990. The effectiveness of the
sterile insect technique must be improved, however, to make it a more effective tool
for eradicating caribfly populations from localized areas during establishment of fly-free
zones. For this technique to be effective, the flies released must be vigorous and be
able to compete with wild males for wild females. Although the FDACS-DPI Caribbean
fruit fly rearing facility in Gainesville has a stable production of healthy flies, improve-
ment in rearing efficiency might be achieved by a better understanding of the nutritional
requirements of the fly.
A method to select against one gender of a population of insects being reared is
termed genetic sexing. The technique consists of a genetically inherited factor being
identified that can be manipulated, such as resistance or unusual susceptibility to a
chemical. The gene(s) responsible are transformed to the sex chromosome, in the case
of a resistant factor, to the Y-chromosome. When the toxic chemical is induced, one of
the sexes is eliminated. Development of such a genetic sexing technique would permit
the rearing of males only. If induced early in the rearing process, it would reduce
rearing costs by half. It would also ensure that only sterile males would be released
against the wild populations. This would increase the pressure on the unmated wild
females. Early applications of sterile male only releases have shown that this technique
has increased the effectiveness of the SIT on medflies tremendously in Hawaii (W.
Klassen, IAEA, Vienna, Austria, pers. commun.). Efforts in this direction with
caribflies are being pursued by Dr, Handler and colleagues in Gainesville.
A quality control system has been developed for mass-reared fruit flies (Boller et
al. 1981, Calkins et al. 1982), particularly medflies, as a laboratory bioassay to monitor
the rearing procedure. It is also used to gain insight into how effective the flies may be
when released into the field (Chambers et al. 1983). We have adapted the techniques
developed for medfly to the caribfly situation. There is a strong correlation between
flight ability tests and longevity tests in the laboratory with dispersal rates and survival
in the field (COC & Wm. Schroeder, unpub. data). The bottom line is, however, the
actual mating and sperm transfer from sterile males to fertile females. Mating propen-
sity test results for sterile and fertile flies in laboratory and field cages are similar.
However, there is no easy way to evaluate the mating success in the field. Development
of a sperm marker that could be used to determine if a wild female was inseminated by
a sterile male would solve this problem. This would have positive ramifications in
evaluating the effectiveness of the SIT but could also affect the protocol of the fly-free
zones. Discovery of a wild female in the zone now causes the loss of certification for a
period of time. However, if the female were proven to have been inseminated by a
sterile male, certification would probably not be removed.
Development of a system to determine the age of adults trapped in the field would
be another way of evaluating the effect of an autocidal eradication program. This would
determine the age structure of the population and assist in the development of a demo-
graphic model. Such a model would indicate whether the population is increasing or
decreasing, thus indicating whether long-term control measures are becoming effective.
R. Heath, J. Sivinski (USDA ARS, Gainesville, FL) and R. Baranowski (Univ. Florida,
Homestead) are currently looking at the level of pteridine in the eye of flies to see if
levels correlate with age.










Florida Entomologist 76(2)


June, 1993


The discovery and use of a powerful attractant together with visual cues and a
persistent toxicant could result in the employment of male or female annihilation tech-
niques. With this technique in place, the population could be reduced or eliminated by
use of traps or attractants. This technique is, and has been used, for eradication of the
melon fly, Bactrocera cucurbitae (Coquillett) and the oriental fruit fly, B. dorsalis
(Hendel) in California.
The area of biological control is just beginning to have some impact on wild fly
populations. A pilot test involving an integration of inundative releases of parasites and
sterile flies for suppression of caribfly populations is being conducted as a cooperative
effort by ARS (Drs. Sivinski and Calkins), IFAS (Dr. Baranowski), FDACS-DPI (Mr.
Ed Burns, Mr. Don Harris, Mr. Jose Diaz and others) and USDA-APHIS (Mr. Tim
Holler). This study, being conducted on Key Biscayne and in Clewiston, is designed to
reduce populations of caribflies throughout the year. Early results are encouraging.
There has been a significant reduction in populations of the caribfly when the two
methods are used together and when parasites are released alone throughout the year.
Parasites and sterile flies released together or in tandem could serve to protect fly-free
zones from invasion of populations from urban/suburban areas. If sterile flies and/or
parasites were released outside of the certified areas in bordering urban and residential
areas during the grapefruit harvest season, the resident population would be severely
suppressed and there would be no migration from these areas into the citrus groves.
Under the protocol, if unmarked flies are caught in the fly-free zones, those affected
groves lose their certification.
Improvement in parasite rearing and efficiency of the program will be necessary to
treat large areas. The parasite, Diachasmimorpha (Biosteres) longicaudata (Ashmead)
(Hymenoptera: Braconidae), was selected for the pilot test because it was easy to rear
and because it is presently the dominant parasite of A. suspense in Florida. The rearing
techniques were developed at the ARS Tropical Fruit and Vegetable Research Labora-
tory in Honolulu, Hawaii (Wong et al. 1990). They were improved upon by J. Sivinski
(USDA ARS) and adapted to the large rearing scheme by Ed Burns (FDACS-DPI).
There may be more effective parasites that have not yet been discovered.
Explorations for parasites of Anastrepha in Latin America have been conducted
only on a limited basis. Norrbom (1985) indicated that 185 Anastrepha species are
endemic to the American tropics and subtropics. Parasites attacking other species of
Anastrepha in Latin America may be compatible with A. suspense and adaptable to
the Florida environment. The parasite used in the pilot test, Diachasmimorpha lon-
gicaudata is from Southeast Asia, where Anastrepha or Ceratitis do not exist, yet it is
quite compatible with the caribfly and the medfly. ARS is embarking on a program of
fruit fly exploration in Latin America.
Parasites that are presently available and any new ones brought in must be
evaluated for their suitability to infest the caribfly under a variety of conditions. At-
tempts must be made again to establish some of the fruit fly parasites found in Hawaii.
If specimens are brought here and held in quarantine and reared in the laboratory
colony, releases could be made in several different environmental sites at various times
of the year. This would enhance the chances of establishment in Florida.

CONCLUSIONS

There are many areas of research on caribflies. Research must be focused on the
needs of industry and those of action and regulatory agencies, without losing sight of
the basic studies that lay the groundwork for future breakthroughs in control strategies.
I anticipate that with this approach, breakthroughs will occur that will transform the
caribfly from a major pest of citrus to only an occasional problem that would not threaten
the export industry nor prove a threat to other states.










Caribbean fruit fly '91: Calkins


REFERENCES

ANONYMOUS. 1986. U. S. Dept. of Agriculture, Animal and Plant Health Inspection
Service, Plant Protection and Quarantine and Florida Dept. of Agriculture and
Consumer Services, Div. Plant Industry, Bureau of Plant Inspection. 1986.
Florida Fruit Fly Detection Manual. Loose-leaf pub. n.p.
ANONYMOUS. 1990. Japan-United States Caribfly Protocol on Fresh Florida Fruit.
Florida Dept. of Agriculture and Consumer Services, Div. of Plant Industry
Report. 12 pp.
BEAVERS, J. B., AND C. O. CALKINS. 1984. Susceptibility of Anastrepha suspense
(Diptera: Tephritidae) to steinernematid and heterorhabditid nematodes in labo-
ratory studies. Environ. Entomol. 13: 137-139.
BOLLER, E. F., B. I. KATSOYANNOS, U. REMUND, AND D. L. CHAMBERS. 1981.
Measuring, monitoring and improving the quality of mass-reared Mediterranean
fruit flies, Ceratitis capitata Wied. 1. The RAPID quality control system for
early warning. Z. ang. Entomol. 92: 67-83.
CALKINS, C. O., D. L. CHAMBERS, AND E. F. BOLLER. 1982. Quality control of fruit
flies in a sterile insect release programme, pp. 341-55. In Sterile Insect Technique
and Radiation in Insect Control. International Atomic Energy Agency IAEA-
SM-255/37. Vienna.
CALKINS, C. O., AND J. C. WEBB. 1988. Temporal and seasonal differences in movement
of the Caribbean fruit fly larvae in grapefruit and the relationship to detection
by acoustics. Florida Entomol. 71(4): 409-416.
CHAMBERS, D. L., C. O. CALKINS, E. F. BOLLER, Y. ITO, AND R. T. CUNNINGHAM.
1983. Measuring, monitoring and improving the quality of mass-reared Mediter-
ranean fruit flies, Ceratitis capitata (Wied.). 2. Field tests for confirming and
extending laboratory results. Z. ang. Entomol. 95(3): 285-303.
CHUMAN, T., J. SIVINSKI, R. R. HEATH, C. 0. CALKINS, J. H. TUMLINSON, M. A.
BATTISTE, R. L. WYDRA, L. STREKOWSKI, AND J. L. NATION. 1988. Suspen-
solide, a new macrolide component of male Caribbean fruit fly (Anastrepha sus-
pensa) [Loew] volatiles. Tetrahedron Letters 29(50): 6561-6564.
GREANY, P. D., R. E. MCDONALD, W. J. SCHROEDER, AND P. E. SHAW. 1991.
Improvement in efficacy of gibberellic acid treatments in reducing susceptibility
of grapefruit to attack by Caribbean fruit fly. Florida Entomol. 74(4): 570-580.
GREANY, P. D., S. C. STYER, P. L. DAVIS, P. E. SHAW, AND D. L. CHAMBERS.
1983. Biochemical resistance of citrus to fruit flies. Demonstration and elucidation
of resistance to the Caribbean fruit fly, Anastrepha suspense. Entomol. Exp. &
Appl. 34: 40-50.
LANDOLT, P. L., R. R. HEATH, H. R. AGEE, J. H. TUMLINSON AND C. O. CALKINS.
1988. Sex pheromone-based trapping system for papaya fruit fly (Diptera: Tep-
hritidae). J. Econ. Entomol. 81: 1163-1169.
NATION, J. L. 1975. The sex pheromone of Caribbean fruit fly males: Isolation, biolog-
ical activity and partial characterization. Environ. Entomol. 4:27-30.
NORRBOM, A. L. 1985. Phylogenetic analysis and taxonomy of the cryptostrepha,
daciformia, robusta, and scheusi species groups of Anastrepha Schiner (Diptera:
Tephritidae). Thesis. Penn. State Univ. 355 pp.
SHAW, P. E., C. 0. CALKINS, R. E. MCDONALD, P. D. GREANY, J. C. WEBB, M.
O. NISPEROS-CARRIEDO, AND S. M. BARROS. 1991. Changes in limonin and
naringin levels in grapefruit albedo with maturity and the effects of gibberelic
acid on these changes. Phytochem. 30 (10): 3215-3219.
SIVINSKI, J. M. 1990. Colored spherical traps for capture of Caribbean fruit fly Anas-
trepha suspense. Fla. Entomol. 73: 123-128.
STYER, S. C., AND P. D. GREANY. 1983. Increased susceptibility of laboratory-reared


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vs. wild Caribbean fruit fly, Anastrepha suspense (Loew) (Diptera: Tephritidae),
larvae to toxic citrus allelochemics. Environ. Entomol. 12(5): 1606-1608.
WONG, T. T. Y., M. M. RAMADAN, D. O. McINNIS, N. MOCHIZUKI, J. I. NISHIMOTO
AND J. C. HERR. 1991. Augmentative releases of Diachasmimorpha tryoni
(Hymenoptera: Braconidae) to suppress a Mediterranean fruit fly (Diptera: Tep-
hritidae) population in Kula, Maui, Hawaii. Biol. Control 1: 2-7.













FALL ARMYWORM SYMPOSIUM

PREFACE

CHARLIE E. ROGERS
USDA/ARS
Insect Biology & Population
Management Research Laboratory
Tifton, GA 31793-0748

The Fall Armyworm Symposium, held during the annual meetings of the Southeast-
ern Branch of the Entomological Society of America since 1978, has served as a forum
for scientific exchange of information on this pest of importance in the Americas. The
papers presented have elucidated aspects of fall armyworm systematics, seasonal
habitats and dynamics, migration, host plant resistance, biological and chemical control,
to name a few.
The fall armyworm is a serious pest on corn, sorghum, and related grasses but
attacks other crops as well when conditions are favorable. The extensive area of occur-
rence of this pest at damaging levels presents a challenge to entomologists throughout
the Americas in developing practical and economical control measures. Dispersal of this
insect from potential source areas has not been defined clearly. Migration into areas
where it cannot survive is of international importance. Aspects of systematics of the
species, spread of insecticidal resistance, development of resistant crop plants, and
impact of chemical and biological control present a veritable smorgasbord of research
opportunities for collaborative research among scientists in the Americas. Projects in
these areas provide information essential to the development of integrated pest manage-
ment programs at different levels of crop production technology.
The papers presented here were part of the Fall Armyworm Symposium at the 66th
Annual Meeting of the Southeastern Branch of the Entomological Society of America
in Savannah, Georgia, March 11, 1992. As in previous symposia on the fall armyworm,
these papers represent current research on this pest. This symposium is dedicated to
a scientist who made many valuable contributions to the taxonomy and biology of this
insect: Sir James Edward Smith.


June, 1993










Fall Armyworm '92: Simmons & Wiseman 271

JAMES EDWARD SMITH TAXONOMIC
AUTHOR OF THE FALL ARMYWORM

ALVIN M. SIMMONS1 AND B. R. WISEMAN
Insect Biology and Population Management Research Laboratory,
Agricultural Research Service, U.S. Department of Agriculture,
Tifton, GA 31793-0748

ABSTRACT

Sir James Edward Smith (born 2 December 1759, died 17 March 1828) made many
valuable contributions to the field of science, notably on taxonomy of plants and insects.
Sir James is the sole taxonomic author of the fall armyworm, Spodopterafrugiperda (J.
E. Smith), and numerous other American insects. Many 20th century and earlier writers
have erroneously attributed the taxonomic authorship of the fall armyworm and other
insects to Smith and Abbot because they are co-authors of a 1797 publication describing
those insects. However, the preface of that publication, as well as notes by Abbot,
indicates that Smith was responsible for the systematic names therein. James Smith
was the first president of the Linnaean Society of London. During his long active life,
Smith published over 3,000 articles. The 1992 Fall Armyworm Symposium is dedicated
to Sir James Edward Smith.

RESUME

El caballero James Edward Smith (nacido el 2 de Diciembre de 1759, muri6 el 17 de
Marzo de 1828) hizo muchas contribuciones valiosas a la ciencia, sobresaliendo su aporte
a la taxonomfa de plants e insects. Sir James es el taxonomo de el cogollero del Maiz,
Spodoptera frugiperda (J. E. Smith) y otros insects Americanos. Muchos escritores
del siglo 20 han atribuido la taxonomfa del cogollero y otros insects a Smith y Abbott
porque ellos son coautores de una publicaci6n en 1797 en la cual deseriben estos insects.
Sinembargo, tanto el prefacio de esta publicaci6n, como las notas de Abbott, indican
que Smith fue responsible por estos nombres sistematicos. James Smith fue el primer
president de la Linnean Society de Londres. Durante su vida active, Smith public
mas de 3,000 articulos. El simposio de 1992 del cogollero del maiz es dedicado a Sir
James Edward Smith.




Sir James Edward Smith
2 December 1759 17 March 1828

James Edward Smith, the sole taxonomic author of the fall armyworm, Spodoptera
frugiperda (J. E. Smith), had an active scientific life. Most of his time and many of his
contributions dealt with the taxonomy of plants. However, his contributions to the
taxonomy of insects were significant. Smith and John Abbot published the first exten-
sive illustrated monograph devoted solely to American insects. Much of the information
in the following four paragraphs was summarized from Simpkins (1975).



'Current address: USDA-ARS, U. S. Vegetable Research Laboratory, 2875 Savan-
nah Highway, Charleston, SC 29414.










Florida Entomologist 76(2)


James Edward Smith was born in Norwich, England, and was the oldest of seven
children by James Smith and Frances Kimberly. During his childhood, the younger
Smith had much interest in botany. He had wanted to formally study botany; neverthe-
less, his father, a textile merchant, wanted the younger Smith to also study medicine.
In 1781, he entered the University of Edinburgh to study under John Hope who es-
poused the Linnaean system of plant classification (also called sexual system). Then in
1783, he moved to London to study anatomy under John Hunter. Following the death
of Carolus Linneaus in 1788, Smith purchased the Linnaean collection (library, manu-
scripts, herbarium, and specimens) for about 1,000. James Smith married Pleasance
Reeve in 1796 and moved with her back to Norwich. They also took the Linnaean
collection with them.
The Linnaean collection was a vehicle by which Smith gained much recognition
within the scientific community in London. He studied the specimens and rearranged
and relabeled some of them. Smith published several works based on the manuscripts
of Linnaeus. One of the most important effects of the purchase of the Linnaean collection
was the founding of the Linnaean Society in 1788. Smith was the first president of this
society and remained president for the remainder of his life. Some members resented
that Smith did not leave the collection to the Linnaean Society upon his death. However,
the Society later purchased the collection for 3,000.
Sir James was elected fellow of the Royal Society of London in 1785, and over the
next two years, he traveled in Europe visiting many famous sites, gardens, libraries,
botanical gardens, and famous botanists. Moreover, he earned an M.D. degree in 1786.
Most of his work was on plant taxonomy. Smith instructed the queen and princesses in
botany and in 1814, he was knighted. Sir James regularly lectured at the Royal Institu-
tion and, for a short while, at Cambridge. He was a popular teacher.
Smith grew many of the plants he studied and was in contact with many gardeners
who grew plants from America. He had much pride in that whenever possible, he
personally checked all descriptions that he issued. Important historical contributions of
Smith to the history of botany were his ability to popularize the subject, and his meticu-
lous accuracy and comprehensiveness in describing the flora of Great Britain and other
countries about which was little known.
According to Simpkins (1975), a complete bibliography of Smith's publications has
never been assembled. She, however, refers to 3,045 articles by Sir James Edward
Smith.


Entomological Work

The most important work of James Edward Smith in entomology was made in collab-
oration with John Abbot. As already noted, they provided the first illustrated, extensive
monograph devoted entirely to North American insects. Moreover, this monograph
gives the taxonomic description of the fall armyworm. The complete title of Smith &
Abbot's 1797 publication is as follows:

"The natural history of the rarer lepidopterous insects of Georgia. Including their
systematic characters, the particulars of their several metamorphoses, and the
plants on which they feed. Collected from the observation of Mr. John Abbot,
many years resident in that country."

Although Abbot had interest in, and painted pictures of different families of insects,
"The work contains only what relates to some of the curious Lepidoptera" (Smith &
Abbot 1797) of North America. It was published in two volumes, both in English and


June, 1993









Fall Armyworm '92: Simmons & Wiseman


French. The work was published in London in 1797. It is bound in red with leather,
stamped in gold with a marble envelope, and has 104 color plates.
There has been some confusion by earlier as well as recent authors about the nomen-
clature and taxonomic authorship of the fall armyworm. The fall armyworm was origi-
nally classified as Phalaena frugiperda by Smith (Smith & Abbot 1797). It was sub-
sequently placed in the genus Laphygma. Todd (1964) published a notification on "A
change in the scientific name of the fall armyworm." The entire note is as follows:

The fall armyworm, previously known as Laphygma frugiperda (J. E. Smith),
must now be called Spodoptera frugiperda (J. E. Smith). The genus Laphygma
Guen6e has been synonymized with Spodoptera GuenBe by Zimmerman (Insects
of Hawaii, vol. 7, p. 331, 1958). He included only the species occurring in Hawaii
mauritia (Bdv.) (the type of Spodoptera), exempta (Wlk.), and exigua (Hbn.)
(formerly placed in Laphygma). He did not specifically include or exclude other
species formerly placed in Laphygma. The new combination, Spodoptera
frugiperda (J. E. Smith), has not appeared in the literature subsequent to 1958.
Therefore notification of the combination is made so that the name will be avail-
able for identification purposes and for use in future biological and ecological
reports."

The above note was the first time the combination Spodopterafrugiperda appeared
in the literature. In related work on the taxonomic classification of Laphygma, Bayer
(1960) compared the valvae of the male genitalia in the genera Prodenia, Laphygma,
and Spodoptera and concluded that they probably belong to the same genus. Before the
fall armyworm was placed in the genus Spodoptera, most researchers designated in
their publications the taxonomic authors as either Abbot & Smith or Smith & Abbot.
Subsequently, researchers have primarily designated the taxonomic author correctly as
(J. E. Smith). Some incorrect variations include Smith, (Smith), and (J. E. Smith, 1797).
Nevertheless, researchers as late as the late 1980's continued to use two taxonomic
authors, i.e., (Abbot and Smith). Moreover, a few papers continued to use the former
genus, Laphygma.
Because of the confusion by numerous 20th century researchers on the taxonomic
authorship of the fall armyworm, Wilkinson (1981) published an article explaining why
James Edward Smith should be listed as the sole author. Abbot, a London naturalist
with proficiency in art, entomology, and ornithology, emigrated to the American col-
onies in 1773. Smith is the editor of their 1797 work. The nature of the collaboration
between Smith and Abbot is described in the preface of Smith & Abbot (1797): "The
materials of the following work have been collected on the spot by a faithful observer,
Mr. John Abbot, many years resident in Georgia, who, after having previously studied
the metamorphoses of English insects, pursued his enquiries among those of Georgia
and neighboring parts of North America. The result of his observations he has de-
lineated in a style of beauty and accuracy which can scarcely be excelled, and has
accompanied his figures with an account, as well as a representation, of the plants on
which each insect chiefly feeds, together with many circumstances of its manners, times
of the different metamorphoses, and other interesting particulars. For all such facts
recorded in these pages the public are entirely obliged to Mr. Abbot. His memorandums,
not methodized by himself for publication, have merely been digested into, some sort
of style and order by the editor, who has generally added remarks of his own, in a
separate paragraph and different type from the rest; and who has entirely to answer
for the systematic names and definitions; that department having been left altogether
unattempted by Mr. Abbot." Wilkinson (1981) examined Abbot's notes which provide
solid evidence that Abbot did not attempt taxonomic identifications. According to Wil-


273









Florida Entomologist 76(2)


June, 1993


kinson (1981), Abbot's introductory statements to Smith is the key: "As I intended the
following, I think you may still publish it as a separate Work from any other you are
at present engaged in. However if you think otherwise you may only mention my Name
now & then . You may therefore prune and trim what you please of the following
rude Notes, I shall therefore not marshall them in any Order, take them as they occur.
I have not pretended to describe them in any scientific manner, leaving that for you [r]
superior Abilities." As he stated in the preface (Smith & Abbot 1797), Smith certainly
is responsible for the systematic names in their publication.
John Abbot, a son of a lawyer, came to the colonies in North America because of his
interest in nature, notably insects (Mallis 1971). Abbot's non-interest in the systematics
of insects may be further indicated by the fact that insect taxonomists J. A. Boisduval
and J. E. LeConte published similar volumes as Smith & Abbot (1779) but did not give
credit to Abbot (Mallis 1971). John Francillon, Abbot's agent in London sold many of
Abbot's drawings and insect specimens. Abbot's avocation was nature as exemplified
in the preface of Smith & Abbot (1797): "Many American caterpillars sting like a nettle,
raising little white blisters in the skin, especially when accidentally or slightly touched;
hence they are in general held in great abhorrence. Mr. Abbot however observes, that
he never yet found any caterpillar that it was really dangerous to handle; and he has
often permitted the most stinging kinds to fall upon his hand, or into his bosom, to the
great admiration of the negroes, as well as of the white inhabitants."
The publication of Smith & Abbot (1797) was restricted to Lepidoptera, even though
"North America, according to Mr. Abbot's observations, produced a number of curious
species of insects, very different from those of England, most of them dispersed through
the whole country." The following is an excerpt from Smith & Abbot (1797), volume 2,
page 191, which is the complete English text of information on the fall armyworm
therein.
"TAB. XCVI.



PHALAENA FRUGIPERDA

Corn-Bud-Worm Moth



Holcus Bicolor. Arduin. Monogr. 25. T.6.

Black and White Guinea Corn.



Ph. Noctua spirilinguis cristata, alis deflexis:
primoribus fusco nebulosis punctis duobus
ocellaribus fuscis litura intermedia
maculaque ad apicem alba

The food of this species is the Guinea corn, as well as other kinds of grain, to
which the caterpillar is very destructive, feeding on the bud or main shoot of the
plant, within which it lives. They may sometimes be destroyed in hot weather
by throwing into the bud a handful of hot sand or dirt.


274










Fall Armyworm '92: Simmons & Wiseman


The caterpillar went into the ground July 15th, and the moth came out the
27th. It is not a very frequent occurrence in the winged state.
An evident affinity between this and the last runs through all their three
states.
It is worth the consideration of the husbandman whether, by studying the
natural history of this formidable depredator, he could not get the better of it.
This is most probably to be accomplished while it remains in the egg; for unfor-
tunately it appears to continue so short a time under ground in the pupa, and at
a season when the corn is growing, that plowing it up is impracticable. Would
any kind of fowls feed upon the pupae, and could they get at them while in the
On the opposite page of the text is a drawing of a corn plant, and the pupa, larvae,
and adult female and male of the fall armyworm. The English translation of the Latin
description is "Noctuid, spiral-tongued, crested, with bent wings: fore-wings clouded
with dark color, with two eye-like dark points, with a smear/rubbed effect between and
with a white spot at the tip of the wing." The text on page 191 appears in French on
page 192.
In addition to describing the fall armyworm, Smith is also the taxonomic author of
the following lepidopterans: walnut sphinx (Laothoejuglandis), orangestriped oakworm
(Anisota senatoria), redhumped caterpillar (Schizura concinna), unicorn caterpillar
(Schizura unicornis), smeared dagger moth (Acronicta oblinita), puss caterpillar
(Megalopyge opercularis), whitemarked tussock moth (Orgyia leucostigma), hag moth
(Phobetron pithecium), and banded wollybear (Pyrrharctia isabella) (Smith & Abbot
1797).

SUMMARY

Sir James Edward Smith, who was born and died in Norwich England, made many
valuable contributions to science, namely on taxonomy of plants and insects. He pub-
lished over 3,000 articles. His purchase of the Linnaean collection was valuable in his
taxonomic studies. He became the first president of the Linnaean Society of London
and held that position until he died 40 years later. Sir James' collaboration with John
Abbot resulted in a publication on numerous North American insects. Therein are the
fall armyworm, Spodoptera frugiperda (J. E. Smith), and numerous other species of
insects of which Smith is the sole taxonomic author (Smith & Abbot 1797). A scientist
who is indeed worthy of this honor of the Fall Armyworm Symposium Dedicatee is Sir
James Edward Smith.

REFERENCES CITED

BAYER, M. B. 1960. The valve of the male genitalia in the genera Prodenia, Laphygma
and Spodoptera (Lepidoptera-Noctuidae). S. African J. Agric. Sci. 3(4): 625-631.
MALLIS, A. 1971. American Entomologists. Rutgers University Press, New Jersey,
549 pp.
SIMPKINS, D. M. 1975. Smith, James Edward, p. 471-472 In Dictionary of scientific
biography, C. C. Gillispie. [ed.] Charles Scribner's Sons, New York.
SMITH, J. E., AND J. ABBOT. 1797. The Natural history of the rarer lepidopterous
insects of Georgia. Including their systematic characters, the particulars of their
several metamorphoses, and the plants on which they feed. Collected from the
observation of Mr. John Abbot, many years resident in that country. London,
printed by T. Bensley, 2 V.
TODD, E. L. 1964. A change in the scientific name of the fall armyworm. Coop. Econ.
Insect Rep., Plant Pest Control Div. Res. Serv. U. S. Dept. Agr. 14: 1254.


275










276 Florida Entomologist 76(2) June, 1993

WILKINSON, R. S. 1981. Smith and Abbot, the natural history of the rarer lepidopter-
ous insects of Georgia (1797): its authorship and later history. Entomologist's
Record and J. Variation. 93: 213-218.






HAZARD FOR FALL ARMYWORM (LEPIDOPTERA:
NOCTUIDAE) INFESTATION OF MAIZE IN DOUBLE-
CROPPING SYSTEMS USING SUSTAINABLE
AGRICULTURAL PRACTICES

PHILLIP M. ROBERTS AND JOHN N. ALL
Department of Entomology
University of Georgia
Athens, GA 30602

ABSTRACT

Field tests demonstrated that selected sustainable agricultural practices influence
intensity of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), infestations
of late planted maize, Zea mays, in double cropping systems. Reduced FAW infesta-
tions of seedling maize were associated with no-tillage as compared with plow-tillage
practice. Maize in no-tillage plots required one less chlorpyrifos [0.56 kg (AI/ha] spray
than in plow-tillage based on a 50% action threshold. Surface debris of winter cover
crops influenced lags of FAW infestation on no-tillage maize. Surface residues from
previous cover crops may account for the reduced infestations in no-tillage areas. Infes-
tations among plots became similar as plants grew from within the mulch cover. Use
of poultry manure as a soil amendment had no effect on FAW damage, but a tendency
for increased yields was observed in poultry manure plots. Chlorpyrifos significantly
reduced FAW feeding resulting in increased whole plant dry weight yield in treated
plots.

RESUME

Mediante experiments realizados en el campo se demostr6 que algunas practices de
agriculture sostenible influencian la intensidad de las infestaciones del cogollero del
maiz (FAW), Spodopterafrugiperda (J. E. Smith) en maiz plantado al final de la estaci6n
en sistema de cultivo double. Se asoci6 la reducci6n de infestaciones de FAW en plantulas
de maiz cuando no se labr6 comparado cuando hubo labranza. Al utilizar un nivel
economic de dafo del 50%, el maiz en las parcelas sin labranza necesit6 una asperci6n
menos de chlorpyrifos (0.56 kg ia/ha) que las parcelas con labranza. Los residues de
otros cultivos de cobertura pueden ser responsables por la reducci6n de las infestaciones
en las parcelas sin labranza. Las infestaciones fueron similares entire parcelas cuando
las plants crecieron fuera de la cobertura. El uso de gallinaza como una emmienda al
suelo no tuvo mayor efecto en la infestaci6n de FAW, pero se observe un mayor re-
ndimiento en aquellas parcelas que recibieron la emmienda. El chlorpyrifos redujo el
dafio de FAW, lo cual result en un incremento en el peso seco de toda la plant en las
parcelas tratadas.


-^^^








Fall Armyworm '92: Roberts & All 277

A rapidly growing interest in sustainable agricultural practices has occurred in re-
cent years. Reducing dependence on chemical control of insect pests, minimizing soil
erosion, and decreasing use of petroleum fertilizers are of particular interest for future
agricultural systems (Robbins 1988). In the southeast, producers have a longer growing
season than other regions and double cropping of maize, Zea mays, or other field crops
is feasible following a winter crop. However, increased hazard of pest infestation is
often associated with double-cropping systems because later than normal planting dates
for field crops are sometimes necessary (All 1989). For example, the fall armyworm
(FAW), Spodoptera frugiperda (J. E. Smith), can produce severe infestations in late
planted maize in double-cropping systems.
The objective of this study was to determine if selected sustainable agricultural
practices create hazardous environments for FAW infestations in double-cropping sys-
tems and to evaluate their compatibility with conventional IPM practices established
for FAW.

MATERIALS AND METHODS

Field experiments were conducted during 1989-1991 at the University of Georgia
Plant Sciences Farm near Athens, GA. A tropical maize cultivar, XL678-C, was planted
using a John Deere Flex 71 no-till planter in either no-tillage or plow-tillage after
harvest of selected winter cover crops. Other cropping practices evaluated included use
of chlorpyrifos at 0.56 kg (AI)/ha, poultry manure, or a combination of the materials.

Cover Crops

A randomized complete block split-split plot design was used with winter cover crop
areas as main plots. Cover crops were established in the fall of 1989 and 1990 using
standard agricultural practices. Winter cover crops included: Canola, Brassica napus,
which is a potential winter cash crop in the southeast, crimson clover, Trifolium incar-
natum, which may be incorporated as a green manure, and wheat, Triticum aestivum,
which is commonly grown in the southeast as a winter cash crop. General observations
were made at three week intervals on ground coverage: light (<20%), moderate (<50%),
or high (>50%)) of the detritus produced by each of the cover crops on the soil surface
of the no-tillage plots.

Cultural Practices

Subplots included no-tillage or plow-tillage areas measuring 75 m2. No-tillage plots
received no plowing prior to maize planting whereas plow-tillage plots included tillage
operations with a moldboard plow and disk harrow until a smooth seedbed was pre-
pared. Paraquat at 0.70 kg (AI)/ha was applied just prior to planting to kill existing
vegetation. Residual weed control was obtained by applying atrazine at 2.24 kg (AI)/ha
at planting.
Sub-subplots consisting of two 6.1 m rows separated by two border rows included
litter free air-dried poultry manure at 3056 kg/ha applied to the soil surface at planting,
chlorpyrifos at 0.56 kg (AI)/ha, a combination of the materials, and an untreated control.
Plots which did not receive poultry manure were side-dressed with ammonium nitrate
at 112 kg N/ha. Chlorpyrifos was applied over the top with a CO2 backpack sprayer
with a carrying volume of 234 liters/ha. Chlorpyrifos treatments were initiated at 50%
infested plants for either no-tillage or plow-tillage areas (Suber & All 1980). Whole plant
yield was determined in each plot by harvesting all plants in the middle 5 m of each row.









Florida Entomologist 76(2)


Insect Sampling

Fall armyworm infestations were sampled at periodic intervals to determine if
thresholds for insecticide application had been reached. In 1990, 100 plants were sam-
pled in no-tillage and plow-tillage and in 1991, 10 plants in each plot were sampled and
data were pooled for tillage regimes. In both years visual estimates of the degree of
plant injury based on a 0-7 scale were scored for each plot. Plants received a 0 rating
when no injury was present; 1 was slight leaf damage (<10%) with no feeding in the
whorl as evidenced by the lack of gummy excrement; 2 was moderate leaf damage
(10-20%) and no whorl feeding; 3 was heavy leaf damage (>20%) and no whorl feeding;
4 was leaf damage <20% and light whorl damage with a slight amount of excrement; 5
was leaf damage (20-40%) with a moderate amount of excrement in the whorl; 6 was
severe leaf feeding (>40%) with a large amount of excrement in the whorl; and 7 was
plants that had leaves with only midribs remaining and buds destroyed (All 1988).
Results of fall armyworm infestation and whole plant maize yield were analyzed with
an analysis of variance (SAS Institute 1985) for a split-split plot design. Treatment
means were separated with Duncan's multiple range test (Duncan 1955).

RESULTS AND DISCUSSION

Cover Crops

Visual evaluation of FAW leaf feeding injury to maize plants in growth stage 1 (four
leaves fully emerged, Hanway 1971) demonstrated that there were no significant effects
(P>0.05) of cover crops on FAW infestations. Mid-season damage ratings of maize
plants in growth stage 3 (twelfth leaf fully emerged) were similar among the cover crops
in both years. Maize following crimson clover yielded significantly higher (P<0.05) in
1990 compared with maize following canola and wheat, but no significant differences in
whole plant yield occurred in 1991 (Table 1).

Tillage

FAW infestations were significantly greater (P<0.05) in the plow-tillage plots as
compared with no-tillage in both years (Figure 1). Observations demonstrated that
oviposition by moths commenced within 24 h of plant germination in the plow-tillage
plots whereas no egg masses, larvae, or leaf injury were observed in the no-tillage plots
for up to seven days after plant germination. Chlorpyrifos treatments were required at
11 and 16 days after planting in plow-tillage maize whereas chemical control was not
necessary until 18 and 28 days after planting in the no-tillage plots in 1990 and 1991,
respectively. As plants increased in size, FAW damage became similar in both systems.
This was demonstrated by the fact that the damage threshold of 50% infested plants
was surpassed in both tillage systems when plants surpassed stage 1 (four leaves fully
emerged).
In 1984 Harrison demonstrated that maize plantings infested in early development
were less tolerant to insect injury than plants infested later. Maize which was infested
with FAW in the first week after germination suffered a 22% yield reduction whereas
plants infested in the second and third weeks experienced a yield reduction of 14%
(Harrison 1984). Results from the present study indicate that utilizing no-tillage prac-
tices reduces hazard of an early FAW infestation during the sensitive period of plant
development when leaf injury results in greatest yield reduction.
Mid-season damage ratings between tillage areas were similar in 1991, but damage


278


June, 1993









Fall Armyworm '92: Roberts & All


TABLE 1. TREATMENT MEANS FOR MID-SEASON FAW DAMAGE RATING AND
WHOLE PLANT DRY WEIGHT MAIZE YIELD FOR MAIN EFFECTS.

1990 1991
Drainage Yield Drainage Yield
Main effect' rating2 (kg/ha)3 rating (kg/ha)

Cover crop
Canola 2.95a 1961a 3.66a 8988a
Clover 2.72a 2932b 3.78a 10590a
Wheat 2.99a 1537a 3.68a 10706a

Tillage
No-Tillage 2.55a 2357a 3.75a 10751a
Plow-Tillage 3.22b 1930a 3.67a 9526a

Sub-subplots
Control 5.18a 915a 5.08a 8487a
Manure 4.85b 1174a 5.15a 9323ab
Chlorpyrifos 0.72c 3210b 2.33b 11202bc
Chlorpyrifos 0.79c 3275b 2.28b 11461c
+ Manure

'Means followed by the same letter within columns for each main effect are not significantly different at P<0.05
(ANOVA, DMRT).
'FAW damage rating on 0-7 scale at 41 and 46 days after planting (plants were in stage 3 of development) in 1990
and 1991, respectively.
'Whole plant dry weight yield 59 and 92 days after planting in 1990 and 1991, respectively.



associated with plow-tillage areas in 1990 was significantly greater (P<0.05) than in
no-tillage areas. Although no-tillage maize received one less insecticide application in
both years, dry weight yields between tillage areas were similar (Table 1).

Cover Crop x Tillage Interactions

Significant cover crop x tillage interactions occurred in 1990 and 1991. FAW infesta-
tions were similar between cover crops within plow-tillage areas, however significant
differences were observed between cover crops in the no-tillage areas (Figure 2). In
1990, interactions between cover crops within no-tillage plots occurred 18 days after
planting (plants were in stage 1 of development) with maize following wheat having a
significantly lower damage rating than maize planted in crimson clover and canola areas.
In 1991, FAW damage to maize was significantly reduced in no-tillage plots of wheat
and crimson clover compared with canola 16 days after planting (plants were in stage
1 of development). One week later, significantly less FAW damage was observed in
no-tillage maize following wheat compared with crimson clover and canola.
In 1988, the junior author observed less FAW feeding damage in no-tillage areas
10-15 days after planting and speculated that an inability of adults to locate maize
seedlings within the mulch was responsible for reduced feeding in no-tillage systems.
Studies by Altieri (1980) on FAW infestations in maize-bean polycultures suggested
that amount of interference associated with bean mass may disrupt FAW infestations.
When beans were planted 20 and 30 days before maize, the number of FAW larvae


279








Florida Entomologist 76(2)


June, 1993


5
NT 1990
ta 4
PT



41-
3







0
11 18 28 34
80
S1991

S60





S20


0 -
16 23 30 38

Days After Planting

% Significantly different at p=0.05 (ANOVA).
Fig. 1. Comparisons of fall armyworm infestations in no-tillage and plow-tillage
maize expressed by visual estimates of leaf and whorl damage on a scale of increasing
severity (0-7) in 1990 and percent infested plants in 1991. Chlorpyrifos sprays at 0.56
kg (AI)/ha were initiated on a 50% infested plant action threshold: 1990 sprays were
required 11 (PT only), 18, 28, and 34 days after planting, 1991 sprays were required 16
(PT only), 21, and 30 days after planting.
infesting maize were significantly less than when beans were planted 10 days before to
20 days after maize plantings (Altieri 1980). In a similar study, Van Huis (1981) con-
cluded that the major reason for reduced infestations of FAW in polycultured maize
was reduced oviposition and less dispersal by first-instar larvae. This study supports
an hypothesis that the amount of mulch in no-tillage plots affects the establishment of


280







Fall Armyworm '92: Roberts & All


6
S5 1990
5 Canola

--j 4 Clover
X 3 -3- Wheat

tw
(d 2

cI 1


11 18 28 34
100
,) 1991
0 80
E *
cO 60

S40

k 20

0 ,
16 23 30 38

Days After Planting

Significantly different at p=0.05 (ANOVA)
Fig. 2. Seasonal comparisons of fall armyworm damage of maize following canola,
crimson clover and wheat within no-tillage culture. In 1990 damage was scored on a
scale of increasing severity (0-7) and in 1991 percentage of damaged plants was used.









Florida Entomologist 76(2)


FAW infestations in no-tillage areas. In general, wheat areas had the greatest amount
of surface debris (high surface coverage for up to 60 days after planting) followed by
crimson clover (moderate surface coverage) and canola (low surface coverage). A lag in
FAW establishment of no-tillage areas followed these trends. In later developmental
stages of maize (>stage 1), FAW infestations became similar in all cover crop areas.

Poultry Manure

In 1990, a significant reduction in FAW damage was observed 41 days after planting
(plants were in stage 3 of development), but this did not occur in 1991. Although not
significant, manure plots had greater yields than plots which did not receive manure in
both years.

Chlorpyrifos

FAW damage was significantly reduced by chlorpyrifos at 0.56 kg (AI)/ha in both
years when a 50% action threshold was used for spraying (Table 1). Plots receiving
chlorpyrifos also produced significantly higher yields compared with the control. In
1990, yields were three times greater in chlorpyrifos treated plots compared to un-
treated areas.

CONCLUSIONS

Results of this study and others indicate that under of high FAW infestations, as
with late planted maize, chemical control applications are necessary to prevent crop
failure. Numerous applications of insecticide for FAW control are not economically
feasible in most cases. In this study, a reduction in the number of insecticide applications
needed to control FAW was observed in no-tillage areas. Hazard of FAW infestations
was reduced by no-tillage when maize seedlings were most vulnerable to yield loss. It
was observed that winter cover crops influence FAW infestations within no-tillage
systems with the amount of debris on the soil surface playing a major role in deterring
FAW infestations. Practices that promote maximum mulch accumulation and retention
might be utilized in IPM programs for FAW in double cropping systems.

REFERENCES CITED

ALL, J. N. 1988. Fall armyworm (Lepidoptera: Noctuidae) infestations in no-tillage
cropping systems. Florida Entomol. 71: 268-272.
ALL, J. N. 1989. Importance of designating prevention and suppression control
strategies for insect pest management programs in conservation tillage, pp. 1-5
in I. O. Teare, E. Brown, and C. A. Trimble [eds.], Conservation farming,
integrated pest management. Proc. southern conservation tillage conf. Univ.
Fla. Press, Sp. Bull 89-91. 86 pp.
ALTIERI, M. A. 1980. Diversification of corn agroecosystems as a means of regulating
fall armyworm populations. Florida Entomol. 63: 450-456.
DUNCAN, D. B. 1955. Multiple range and multiple F tests. Biometrics 11: 1-42.
HANWAY, J. J. 1971. How a corn plant develops. Iowa State University Cooperative
Extension Service special report no. 48. 17 pp.
HARRISON, F. P. 1984. Observations on the infestation of corn by fall armyworm
(Lepidoptera: Noctuidae) with reference to plant maturity. Florida Entomol. 67:
333-335.


282


June, 1993









Fall Armyworm '92: Wiseman & Isenhour 283

ROBBINS, G. J. (ed.). 1988. Alternative Agriculture. 448 pp.
SAS INSTITUTE. 1985. SAS user's guide: statistics, Version 5 edition. Cary, N.C. 956
Pp.
SUBER, E. F. AND J. N. ALL. 1980. Control insects in field corn. University of Georgia
Cooperative Extension Service circular 719. 12 pp.
VN HUIS, A. 1981. Integrated pest management in the small farmer's maize crop in
Nicaragua. Meded. Landbouwhogeschool Wageningen 81-6. The Netherlands.
221 pp.




RESPONSE OF FOUR COMMERCIAL CORN HYBRIDS TO
INFESTATIONS OF FALL ARMYWORM AND CORN
EARWORM (LEPIDOPTERA: NOCTUIDAE)

B. R. WISEMAN AND D. J. ISENHOUR'
U. S. Department of Agriculture, Agricultural Research Service
Insect Biology & Population Management Research Laboratory
Tifton, GA 31793-0748

ABSTRACT

Four commercial hybrids of corn, Zea mays L., were evaluated for their responses
to leaf-feeding by larvae of the fall armyworm, Spodoptera frugiperda (J. E. Smith).
Parameters measured were leaf-feeding damage at 7 and 14 days after infestation, ear
penetration by larvae of the corn earworm, Helicoverpa zea (Boddie), ear and plant
height, days to 50% silk, and yield at maturity. Significant differences were found
among hybrids for all measured parameters except days to 50% silk. Eighty larvae per
plant infested at the 8- or 12-leaf stage resulted in significantly higher leaf-feeding
damage ratings than 40 larvae per plant. Yield reductions were greater at the 8-leaf
stage of infestation (32.4%) than at the 12-leaf stage of infestation (15.4%). Ear and
plant height reductions were similar between the 8- and 12-leaf stages of infestation.
Generally, 80 larvae did not cause a more significant reduction on ear and plant height
than 40 larvae per plant. Plants in the 12-leaf stage tolerated damage better than plants
at the 8-leaf stage of plant development. Although the hybrids tested in this study
differed only in susceptibility, differences among hybrids were significant for leaf-feed-
ing damage, ear penetration by corn earworm, ear and plant height, and yield.

RESUME

Se evaluaron cuatro hibridos comerciales de maiz Zea mays L. para observer su
susceptibilidad a el consume de hojas por larvas del cogollero del maiz, Spodoptera
frugiperda (J. E. Smith). Los parametros utilizados fueron el dafio a las hojas 7-14 dias
despues de infestaci6n, dafo a la mazorca del barrenador del maiz, Helicoverpa zea
(Boddie), altura de la plant, dias para producer 50% de pelusa, y rendimiento en estado


'Pioneer Hi-Bred International, Johnston, Iowa 50131-0085









284 Florida Entomologist 76(2) June, 1993

de madurez. Se encontraron diferencias significativas entire los hibridos para casi todos
los parametros con excepci6n del nimero de dias para producer 50% de pelusa. Al
infestar la plant con 80 larvas durante su estado de 8-12 hojas/planta result en un
dafio significativamente mayor de dafio a las hojas que cuando se utilizaron 40 larvas
por plant. La reducci6n del rendimiento fue mayor en el estado de 8 hojas (32.4%) que
en el estado de 12 hojas (15.4%). Reducciones similares fueron observadas en la altura
y numero de mazorcas en los estados de 8-12 hojas. Generalmente, no hubo reducci6n
significativa de la altura de la plant y del numero de mazorcas cuando 40-80 larvas
infestaron la plant. Plantas en estado de 12 hojas toleraron mas dafo que aquellas de
8 hojas. Aunque los hibridos probados en este studio fueron poco diferentes en suscep-
tibilidad, las diferencias entire hibrido fueron significativas en el dafio de hojas, a las
mazorcas, altura de la plant y rendimiento.





Field corn, Zea mays L., is the most valuable cereal crop in the United States.
Although the amount of corn planted and the value of the crop fluctuate annually, 58.2
million acres were planted in 1988 in the United States with a production of 4.9 billion
bushels and a value of 12.6 billion dollars (United States Department of Agriculture,
1990). Corn is a crop upon which fall armyworm, Spodoptera frugiperda (J. E. Smith),
infestations often reach devastating levels. The fall armyworm is especially damaging
to corn in the southeastern United States. In 1975, losses in Georgia were estimated at
over 20 million dollars (Sparks 1979). Yield losses attributed to the fall armyworm for
the U. S. have been estimated at 2% annually (Wiseman and Morrison 1981).
Plant resistance as nonpreference, antibiosis, and/or tolerance could reduce damage
by the fall armyworm that would be biologically, economically, environmentally, and
socially acceptable to growers and would contribute to the management of the pest over
a large area. Many cultivars of corn have been identified and/or released to the public
that possess intermediate levels of nonpreference and/or antibiosis resistance to fall
armyworm (Wiseman 1985, Wiseman & Davis 1990). Wiseman et al. (1983) showed that
fall armyworm larvae placed on a resistant cultivar, Antigua 2D, tended to migrate
from the plants more than the larvae that were placed on a susceptible cultivar. Wise-
man et al. (1981) and Williams et al. (1983) found significant levels of antibiosis among
selected corn cultivars and that consumption of foliage on a susceptible cultivar was
almost three times greater than on the resistant cultivar.
To begin any new type of plant resistance investigation, one of the first plant sources
to evaluate is adapted materials that are readily used by the growers (Wisenan 1985).
For corn, this would be commercial hybrids. Therefore, this study reports results of an
evaluation of the responses of four commercial corn hybrids to infestations by larvae of
the fall armyworm and the corn earworm.

MATERIALS AND METHODS

Four commercial hybrids, Pioneer 3030 (Pio:3030), Pioneer 3369A (Pio:3369A), Funk
4507A (FK:4507A), and Dekalb XL395 (DK:XL395) were selected for this study. Two
separate plantings were made on the Coastal Plain Experiment Station farm at Tifton,
Ga., in 1989 using agronomic practices common to the area. The experimental design
for each planting was a split-split-plot with seven replications. Whole plots were number
of neonate larvae (40 or 80) per plant. Subplots were noninfested and infested plants
bordered by three rows of a mixture of commonly grown commercial hybrids, and the
final split consisted of the four commercial hybrids. The hybrids were planted in 6.1-m
rows 76-cm apart; plants were thinned to about 30 cm apart.









Fall Armyworm '92: Wiseman & Isenhour


At the 8- (V4) and 12- (V8) leaf stages of development (Ritchie & Hanway 1982) for
planting one and planting two, respectively, each plant within an infested treatment
plot had 40 or 80 neonate fall armyworm larvae placed within the whorl of the plant
(Wiseman et al. 1980a). Plots were visually rated at 7 and 14 days (Diawara et al. 1992)
using a scale of 0-9. For rating at 7 days after infestation, 0 = no damage, 5 = more
than five small (up to 1 cm) elongated holes and four to five medium (1 to 3 cm) elongated
holes on the whorl and/or furled leaves, and 9 = many (>5) elongated holes on whorl
and furled leaves plus elongated or irregular portions of the furled leaves, including
basal membrane eaten. For the rating at 14 d after infestation, 0 = no damage, 5 =
more than five large (> 3 cm) elongated holes on a few whorls and furled leaves and/or
three or less small to medium sized portions eaten from the whorls and furled leaves,
and 9 = plant almost totally destroyed. All noninfested plants were sprayed with bifen-
thrin (0.08 kg ai/ha) on a weekly basis to prevent any damage from migrating fall
armyworm larvae. Days to 50% silking were recorded for each treatment plot. At 21
days post silking, ear and plant height (cm) as well as ear penetration by larvae of the
corn earworm, Helicoverpa zea (Boddie), were recorded for both infested and nonin-
fested plots (Wiseman 1989). At maturity, all ears from 15 plants within each treatment
plot were harvested, shelled, and dried to 15.5% moisture. Yield was recorded in grams
of grain per 15 plants and expressed in k/ha based on 35,879 plants/ha.
Data for each parameter measured were analyzed by ANOVA procedure (SAS Insti-
tute 1985). Means were separated by the appropriate Waller-Duncan k-ratio t test, k
ratio = 100, (Waller and Duncan 1969), Least Squares Means or LSD (SAS Institute
1985), P s 0.05.

RESULTS AND DISCUSSION
The visual rating system for fall armyworm damage has been used since 1964 (Wise-
man et al. 1966) when they were able to consistently separate small differences in
leaf-feeding damage between cultivars evaluated for leaf-feeding resistance. The visual
rating scale has been used to detect minor differences among genotypes as well as
among segregating plants (Widstrom et al. 1972). These differences in leaf-feeding dam-
age have been repeatable and have been separated statistically by as little as one-half
of a rating. It has also been used to separate genotype leaf-feeding differences for
damage by the corn earworm (Wiseman et al. 1976) and in sorghum by Diawara et al.
(1992) in which they found a new type of nonpreference to the fall armyworm. The visual
rating scale has been used to demonstrate position effects of the resistant and suscepti-
ble cultivar and the time to rate to obtain the necessary leaf-feeding differences (Wise-
man et al. 1980b). The visual rating scale used to measure leaf-feeding damage by the
fall armyworm has been an extremely valuable tool in that a number of corn genotypes
have been developed and released to the public (Wiseman and Davis 1990).
Two-way interactions at the 8-leaf stage of plant development occurred for the 7-
and 14-day leaf-feeding damage ratings between the noninfested and infested and the
hybrids as well as the levels of infestation (40 or 80 larvae per plant), and the noninfested
and the infested treatments. No damage was found on the control plots for any of the
hybrids at the 8-leaf stage of development (Table 1). However, significant differences
in visual damage ratings were found among the four hybrids for the treated plots at the
8-leaf stage for both the 7- and 14-day ratings. Pio:3369A, generally considered a suscep-
tible check for most of our past studies (Wiseman 1985), was the least damaged of the
selected commercial hybrids at both the 7- and 14-day ratings. Eighty larvae per plant
at the 8-leaf stage of plant development produced a significantly higher level of leaf-feed-
ing damage than 40 larvae per plant at both the 7- and 14-day ratings (Table 2). Also,
infested plots received significantly more damage than the noninfested plots at the
8-leaf stage of development.


285










Florida Entomologist 76(2)


TABLE 1. MEAN VISUAL RATINGS OF LEAF DAMAGE BY THE FALL ARMYWORM ON
SELECTED COMMERCIAL HYBRIDS COMBINED OVER INFESTATIONS OF
40 OR 80 NEONATES PER PLANT.'

8-Leaf stage

7-Day rating 14-Day rating

Hybrids2 Noninfested Infested Noninfested Infested

DK:XL395 0.0 a 5.4 a 0.0 a 8.3 a
FK:4507A 0.0 a 5.3 ab 0.0 a 8.4 a
Pio:3030 0.0 a 4.8 b 0.0 a 8.3 a
Pio:3369A 0.0 a 4.1 c 0.0 a 7.5 b
SEM 0.19 0.19 0.11 0.11

'Means within a column followed by the same letter are not significantly different, P 0.05 according to the
Waller-Duncan k-ratio t test, and k-ratio = 100 (SAS Institute 1985; Waller and Duncan 1969). Leaf damage rated
on a 0-9 scale (Diawara et al. 1992). SEM = Standard error of the mean.
'Hybrids = DK: DeKalb; FK: Funk; and Pio: Pioneer.


An interaction occurred at the 12-leaf stage between the levels of infestation (40 or
80) and the noninfested and the infested plots similar to that reported for the 8-leaf
stage (Table 2). Significant differences were detected between the levels of infestation
(40 vs. 80) for the 7-day ratings at the 12-leaf stage. A two-way interaction at the 12-leaf
stage of plant development was also found between the noninfested and infested treat-
ments and the hybrids (Table 3). No damage existed in the noninfested plots at 7 or 14
days. Both FK:4507A and Pio:3369A were significantly less damaged at 7 days than
Pio:3030 and DK:XL395, but at 14 days only Pio:3368A was significantly less damaged
than the other three hybrids. Significant differences were found between the nonin-
fested and the infested plots for both the 7- and 14-day ratings. No differences were
found between the levels of infestations (40 vs. 80) at the 14-day rating.
Differences in damage by the corn earworm could be expected when genotype matur-
ity is delayed differentially by a few days. However, no differences in the depth of ear


TABLE 2. MEAN VISUAL RATINGS OF LEAF DAMAGE BY THE FALL ARMYWORM
COMBINED OVER HYBRIDS AFTER INFESTING WITH 40 OR 80 NEONATE
LARVAE PER PLANT.1

8-Leaf stage


7-Day rating 14-Day rating
No. larvae
per plant Noninfested Infested Noninfested Infested

40 0.0 a 4.0 a 0.0 a 7.8 a
80 0.0 a 5.8b 0.0 a 8.5 b
Mean 0.0 4.9 0.0 8.2
SEM 0.20 0.20 0.12 0.12

'Means within a column not followed by the same letter or separated by are significantly different, P < 0.05
according to the Least Squares Means (SAS Institute 1985). Leaf damage rated on a scale of 0-9 (Diawara et al.
1992). SEM = Standard error of the mean.


June, 1993


286









Fall Armyworm '92: Wiseman & Isenhour 287

TABLE 3. MEAN VISUAL RATINGS OF LEAF-FEEDING DAMAGE BY THE FALL AR-
MYWORM COMBINED OVER LEVELS OF INFESTATION WITH 40 OR 80
NEONATES PER PLANT AT THE 12-LEAF STAGE OF PLANT DEVELOP-
MENT.'

12-Leaf stage

7-Day rating 14-Day rating

Hybrids2 Noninfested Infested Noninfested Infested

Pio:3030 0.0 a 6.4 a 0.0 a 8.4 a
DK:XL395 0.0 a 6.6 a 0.0 a 8.2 a
FK:4507A 0.0 a 5.6 b 0.0 a 8.1 a
Pio:3369A 0.0 a 5.7 b 0.0 a 7.4 b
SEM 0.19 0.19 0.13 0.13

'Means within a column followed by the same letter are not significantly different, P s 0.05 according to the
Waller-Duncan k-ratio t test, and k-ratio = 100 (SAS Institute 1985; Waller and Duncan 1969). Leaf damage rated
on a scale of 0-9 (Diawara et al. 1992). SEM = Standard error of mean.
'Hybrids = DK: DeKalb; FK: Funk; and Pio; Pioneer.


penetration by larvae of the corn earworm were found among noninfested hybrids nor
those that had previously been infested with fall armyworm at the 8-leaf stage of devel-
opment (Table 4). No differences in days to 50% silk were detected between levels of
infestation, infested or noninfested treatments, or among the hybrids. Yet, significant
differences were recorded among hybrids at the 12-leaf stage in the depth of ear penet-
ration by larvae of the corn earworm, whether the hybrids had previously been infested
with fall armyworm or not.
Both levels of infestation affected the hybrids similarly for ear height when fall
armyworm larvae were infested at the 8-leaf stage of development; thus, the data were
combined for presentation (Table 5). FK:4507A and Pio:3369A had ear heights less than
DK: XL395 and Pio: 3030 as a result of fall armyworm feeding. A two- way interaction
existed for the 12-leaf stage of plant development for the levels of infestation and hybrid
treatments. Although the interaction occurred, both FK:4507A and Pio:3369A had simi-


TABLE 4. MEAN EAR PENETRATION BY LARVAE OF THE CORN EARWORM ON
SELECTED COMMERCIAL HYBRIDS WHICH HAD PREVIOUSLY BEEN IN-
FESTED WITH 40 OR 80 NEONATE FALL ARMYWORM.'

Mean ear penetration (cm)

Hybrids 8-Leaf stage 12-Leaf stage

FK:4507A 7.0 a 8.0 a
Pio:3369A 6.5 a 6.9 b
DK:XL395 6.1 a 6.2 c
Pio:3030 5.9 a 6.0 c
SEM 0.3 0.2

'Means within a column followed by the same letter are not significantly different, P 0.05 according to the
Waller-Duncan k-ratio t test, and k-ratio = 100 (SAS Institute 1985; Waller and Duncan 1969). Corn earworm depth
of penetration measured according to Wiseman (1989). SEM = Standard error of the mean.










Florida Entomologist 76(2)


TABLE 5. MEAN EAR HEIGHT OF FOUR COMMERCIAL HYBRIDS AFTER INFESTING
WITH 40 OR 80 NEONATE FALL ARMYWORM AT THE 8- AND 12-LEAF
STAGE OF PLANT DEVELOPMENT.'

Ear height (cm)

8-Leaf stage 12-Leaf stage

Hybrids Combined 40 Larvae 80 Larvae

DK:XL395 88 a 90 a 91 b
FK:4507A 81 b 77 b 81 c
Pio:3030 91 a 89 a 101 a
Pio:3369A 76 c 77 b 76 c
SEM 2.39 2.22 2.22

SMeans within a column followed by the same letter are not significantly different, P < 0.05 according to the
Waller-Duncan k-ratio t test, and k-ratio = 100 (SAS Institute 1985; Waller and Duncan 1969). SEM = Standard
error of the mean.


lar ear heights at the 40 and 80 larvae per plant infestation. At the 12-leaf stage, the
average ear height for the control plots was significantly higher (87 cm) as compared
with the height of the ears for the infested plots (84 cm).
Resultant plant height was also significantly influenced by the feeding of the fall
armyworm (Table 6). Again, both FK:4507A and Pio:3369A were significantly shorter
at maturity when infested at the 8-leaf stage than either DK:XL395 or Pio:3030. How-
ever, both FK:4507A and Pio:3369A were shorter when no larvae had fed on them. Yet,
there were significant reductions in heights for all four hybrids when the fall armyworm
were introduced at the 8-leaf stage. A two-way interaction was found between levels
of infestation and hybrids for plant height as a result of infestations at the 12-leaf stage
of development when infested with either 40 or 80 larvae per plant. Both FK:4507A
and Pio:3369A were significantly shorter than the other two hybrids when infested with
40 or 80 larvae per plant. At the 12-leaf stage, the average height of the corn in the


TABLE 6. MEAN PLANT HEIGHT OF FOUR COMMERCIAL HYBRIDS AFTER INFEST-
ING WITH 40 OR 80 NEONATE FALL ARMYWORM AT THE 8- AND 12-LEAF
STAGE OF PLANT DEVELOPMENT.1

Plant height (cm)

8-Leaf stage 12-Leaf stage

Hybrids Noninfested Infested Mean 40 larvae 80 larvae

DK:XL395 231 222 227 b 219 b 227 b
FK:4507A 222 201 212 c 199 c 202 c
Pio:3030 243 232 238 a 232 a 250 a
Pio:3369A 221 201 211 c 204 c 204 c
SEM 2.75 2.75 1.94 2.88 2.88

'Means within a column followed by the same letter are not significantly different, P s 0.05 according to the
Waller-Duncan k-ratio t test, and k-ratio = 100 (SAS Institute 1985; Waller and Duncan 1969). Horizontal means
separated by are significantly different P s 0.05 according to the Least Squares Means, (SAS Institute 1985). SEM
= Standard error of the mean.


June, 1993


288









Fall Armyworm '92: Wiseman & Isenhour 289

control plots was significantly taller (226 cm) as compared with the infested plots (208
cm).
The most important factor in the responses of these or any hybrids to damage by
the fall armyworm is grain yield. A significant difference in yield for the 8-leaf stage
infestation occurred between the control at 6630 k/ha as compared with 4478 k/ha for
the infested plots. At the 8-leaf stage, significant differences in yield between the control
and the infested plots were found for each hybrid and also overall between hybrids
(Table 7). At the 12-leaf stage, a two-way interaction was found between the yields of
the control and infested treatments and hybrid treatment. Differences in yield between
the control and the infested were only found for DK:XL395 and Pio:3030. Also, signifi-
cant differences in yields were found between hybrids within the controls and within
the infested treatments (Table 7). Cruz and Turpin (1983) found significant yield losses
of 17% when 20 or 100% of the plants in the 8-10 leaf stage received egg masses of about
50 eggs. In the present study, overall losses of 32.4% and 15.4% occurred at the 8-leaf
stage after infesting with 40 or 80 neonates.
In summary, infestations of 40 or 80 neonate fall armyworm larvae per plant caused
reductions in ear and plant height and yield (Table 8 and Fig.l), and showed differences
in damage among hybrids for leaf-feeding by larvae of the fall armyworm. Eighty larvae
per plant resulted in a significantly higher leaf-feeding damage rating than 40 larvae
per plant when averaged over all four hybrids. Plant height reductions were significant
among hybrids and similar when infested with 40 or 80 larvae per plant at both the 8-
and 12-leaf stages of plant development (Table 8). Larvae infested at the 8-leaf stage
as compared with the 12-leaf stage caused the more drastic reductions in yield among
these hybrids (Fig.l). Thus, it appears that the older corn plants, i.e., 12-leaf stage,
can tolerate more damage than those at the 8-leaf stage. However, the yield differences
between the 8-leaf stage and 12-leaf stage may also be influenced by infestation date
rather than stage of plant alone. Although yield reductions were quite large, differences
among the four hybrids at the 8-leaf stage were negligible. At the 12-leaf stage, yield
reductions differed among the hybrids. Both FK:4507A and Pio:3369A had average
yield losses of only 7.4% and 9.6%, respectively, while DK:XL395 and Pio:3030 had
average yield losses of 18.4% and 22.7%, respectively. Thus, some of the hybrids
evaluated were more susceptible than others. Yet, mean separation of the measured
parameters of leaf-feeding damage, ear and plant height and yield were significant.


TABLE 7. COMBINED MEAN GRAIN YIELDS OF HYBRID CORN INFESTED WITH 40
OR 80 NEONATE FALL ARMYWORM PER PLANT AT THE 8- AND 12-LEAF
STAGE.

Yield (k/ha)

8-Leaf stage 12-Leaf stage

Hybrids Noninfested Infested Mean Noninfested Infested

DK:XL395 7444 5298 6372 a 7190 a 5860 a
Pio:3030 7224 5145 6183 a 6676 a 5162 b
Pio:3369A 6343 4148 5246 b 5408 b 4892 b
FK:4507A 5511 3325 4416 c 4987 b 4624 b
SEM 196 196 139 198 198

'Means within a column followed by the same letter or column means seaprated by are significantly different,
P s 0.05 according to the Waller-Duncan k-ratio t test, and k-ratio = 100 or Least Squares Means [SAS Institute
1985; Waller and Duncan 1969). SEM = Standard error of the mean.









Florida Entomologist 76(2)


TABLE 8. PER CENT REDUCTION IN EAR AND PLANT HEIGHT AFTER 40 OR 80
NEONATE FALL ARMYWORM WERE INFESTED AT THE 8- AND 12-LEAF
STAGE OF DEVELOPMENT OF FOUR COMMERCIAL HYBRIDS.'

Ear height (cm) Plant height (cm)

8-Leaf stage 12-Leaf stage 8-Leafstage 12-Leafstage

No. larvae/plant No. larvae/plant

Hybrids 40 80 40 80 40 80 40 80
DK:XL395 4.8 3.3 5.4 2.3 6.0 2.6 9.2 9.6
FK:4507A 10.9 5.1 0.0 3.5 12.5 5.9 7.7 11.2
Pio:3030 2.4 9.9 3.1 7.4 0.0 5.3 0.0 5.4
Pio:3369A 0.0 4.5 9.1 0.9 10.0 8.6 9.2 12.1
Mean 4.7 3.7 6.8 8.6
'Per cent reduction = control infested / control X 100.


Fig. 1. Per cent reduction in yield after 40 or 80 neonate fall armyworm were
infested at the 8- and 12-leaf stage of four commercial hybrids.


30-


25-
1 -




20-


10-


52


June, 1993


P3030


S8 Leaf

12 Leaf




















P3369A


F4507A


DXL395










Fall Armyworm '92: Wiseman & Isenhour


ACKNOWLEDGMENT

We thank J. L. Skinner and Charles Mullis of the IBPMRL for their technical
assistance in the entomological phases of this study.



REFERENCES CITED

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armyworm (Lepidoptera : Noctuidae) to midwhorl growth stage of corn. J. Econ.
Entomol. 76: 1052-1054.
DIAWARA, M. M., B. R. WISEMAN, D. J. ISENHOUR, AND N. S. HILL. 1992. Sorghum
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tuidae). J. Agric. Entomol. 9: 41-53.
RITCHIE, S. W., AND J. J. HANWAY. 1982. How a corn plant develops. Iowa State
University Coop. Ext. Ser. Spec. Rpt. 48. 21 pp.
SAS INSTITUTE. 1985. SAS user's guide: statistics, version 5 ed. SAS Institute, Cary,
North Carolina.
SPARKS, A. N. 1979. A review of the biology of the fall armyworm. Florida Entomol.
62: 82-87.
U. S. DEPARTMENT OF AGRICULTURE. 1990. Agricultural statistics, 1990.
Washington, D. C.
WALLER, R. A., AND D. B. DUNCAN. 1969. A bayes rule for the symmetric multiple
comparison problem. J. Amer. Stat. Assoc. 64: 1484-1499.
WIDSTROM, N. W., B. R. WISEMAN AND W. W. MCMILLIAN. 1972. Resistance among
some maize inbreds and single crosses to fall armyworm injury. Crop Sci, 12:
358-359.
WILLIAMS, W. P., F. M. DAVIS, AND B. R. WISEMAN. 1983. Fall armyworm resist-
ance in corn and its suppression of larval survival and growth. Agron. J. 75:
831-832.
WISEMAN, B. R. 1985. Development of resistance in corn and sorghum to a foliar-and
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WISEMAN, B. R. 1989. Technological advances for determining resistance in maize to
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WISEMAN, B. R., AND F. M. DAVIS. 1990. Plant resistance to insects attacking corn
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Florida Entomologist 76(2)


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DISTRIBUTION OF FALL ARMYWORM (LEPIDOPTERA:
NOCTUIDAE) PARASITOIDS ON FIVE CORN GENOTYPES
IN SOUTH GEORGIA

TONI M. RIGGIN,1'2 KARL E. ESPELIE,1 B. R. WISEMAN,3
AND DAVID J. ISENHOUR4',

1Department of Entomology
University of Georgia
Athens, GA 30602

2Current Address: Department of Entomology,
North Carolina State University, Raleigh, NC 27695.

SUSDA-IBPMRL
P. O. Box 748
Tifton, GA 31793

4Department of Entomology
Coastal Plain Experiment Station
University of Georgia
Tifton, GA 31793

5Current Address: Pioneer Hi-Bred International, Inc.,
Department of Research Specialists, Johnston, IA 50131.

ABSTRACT

Five genotypes of corn were planted on four different dates in south Georgia during
the spring of 1991. Plants were infested with neonate fall armyworm (FAW), Spodoptera
frugiperda (J. E. Smith), larvae and collected either seven or twelve days later. Larvae
were reared in the laboratory on artificial diet to determine distribution of FAW
parasitoids. Larvae recovered from the resistant genotype MpSWCB-4 had the highest
percent parasitism (44.30%), while the susceptible genotype Pioneer 3192 had the lowest
parasitism (31.70%). Aleiodes laphygmae (Gahan) was the most abundant parasitoid,
attacking a total of 12.8% of the 16,120 FAW larvae recovered. Archytas marmoratus
(Townsend) parasitized 10.0% of the FAW larvae while Ophion flavidus Brulle and
Cotesia marginiventris (Cresson) parasitized 7.9% and 6.3%, respectively, of the recov-
ered FAW. Ten additional parasitoid species emerged from the FAW, but none of these
species attacked more than 1% of the recovered FAW larvae.


June, 1993


292









Fall Armyworm '92: Riggin et al.


RESUME

Se plantaron cinco genotipos de maiz en cuatro fechas diferentes en el sur de Georgia
durante la primavera de 1991. Las plants fueron infestadas con larvas pequefias del
cogollero del mafz (FAW), Spodopterafrugiperda (J. E. Smith) colectadas siete o doce
dias despubs. Las larvas fueron criadas en el laboratorio en una dieta artificial con el
fin de determinar la distribuci6n de los parasitoides de FAW. Las larvas recolectadas
del genotipo resistente MpSWCP-4 tuvieron el porcentaje mas alto de parasitismo
(44.30%), mientras que el genotipo susceptible Pioneer 3192 tuvo el parasitismo mas
bajo (31.70%). Aleiodes laphygmae (Gahan) fue el parasitoide mas abundante, atacando
un total de 12.8% de 16,120 larvas de FAW. Archytas marmoratus (Towsend) parasit6
10.0% de las larvas de FAW, mientras que Ophion flavidus Brulle and Cotesia mar-
giventris (Cresson) parasitaron 7.9% y 6.3% de las larvas de FAW, respectivamente.
Diez species mas de parasites emergieron de FAW, pero ninguna de estas species
atac6 mas del 1% de las larvas de FAW.




The fall armyworm (FAW), Spodopterafrugiperda (J. E. Smith), is a major pest of
corn, sorghum and peanut, causing more than $60 million damage in the southeastern
United States per year (Sparks 1986). Recently, there has been a substantial amount
of focus on the use of natural enemies as an alternative to pesticide control. Fifty-three
parasitoid species have been reared from FAW larvae collected in the field (Ashley
1979). Several studies have examined the efficacy of selected parasitoids for control of
FAW (Ashley et al. 1982, 1983, Mitchell et al. 1984, Rohlfs & Mack 1985, Gross & Pair
1991). Surveys to determine the natural incidence of FAW parasitoids have shown that
seasonal abundance is variable (Ashley et al. 1980).
The use of resistant host plants to control FAW could have an adverse effect on
FAW parasitoids (Price et al. 1980, Orr & Boethel 1986). However, there are some
cases where parasitism has been enhanced when the host larvae were feeding on resis-
tant plants (Adkisson & Dyck 1980, Isenhour & Wiseman 1987, Riggin et al. 1992b). In
this paper we report the distribution of parasitoids that emerged from FAW larvae
recovered from resistant and susceptible corn genotypes in south Georgia in 1991.

MATERIALS AND METHODS

Test plots were planted 28 March, 12 April, 25 April, and 10 May 1991. Eight
replications of five corn genotypes were planted in a randomized complete block design
which consisted of 6.1 m length double-row plots 0.8m apart. Plantings were made at
the Coastal Plain Experiment Station in Tifton, Georgia. Resistant corn genotypes
were MpSWCB-4 and Pioneer X304C and susceptible corn genotypes were represented
by Cacahuacintle X and Pioneer 3192 (Wiseman et al. 1980b, 1981, Gross et al. 1982).
Pioneer 3140 was the fifth genotype planted.
Plants were infested artificially with 40 neonate FAW larvae per plant (Wiseman et
al. 1980a) when the plants were at the 8-10 leaf stage. Ten plants per plot were collected
7 and 12 d after FAW infestation. The plants were clipped below the whorl, placed in
plastic bags and transported immediately to the laboratory. Each plant that was brought
to the laboratory was thoroughly examined and all FAW larvae were placed individually
in 30-ml cups containing pinto bean diet (Riggin et al. 1992b). FAW recovery was
recorded for each replication. The diet cups containing the FAW larvae were maintained
in the laboratory until the parasitoids had emerged, or until FAW adult emergence.
FAW larvae that were not parasitized and that died prior to pupation were not included
in the tabulations. Parasitoids that emerged were collected and identified by the USDA-


293









Florida Entomologist 76(2)


ARS Systematic Entomology Laboratory, Beltsville, Maryland. Parasitoids were re-
corded according to the corn genotype from which the host FAW had been recovered.
Voucher specimens from this study were deposited in the University of Georgia En-
tomology Museum.
Analysis of the data was made on the log + 1 transformation of the number of
parasitoids for each collection as a stripped-split-plot in time, where parasitoids were
the subplots and the cultivars were the whole plots (SAS Institute 1989). Means were
separated (P < 0.05) according to Waller-Duncan (1969) and total parasitoids collected
are presented.

RESULTS

The numbers of FAW larvae collected from each of the five corn genotypes at 7 and
12 days post-infestation are given in Table 1. The resistant genotype MpSWCB-4 had
the fewest larvae, while the susceptible genotype Pioneer 3192 had the highest number
of FAW larvae collected. The total number of FAW collected between 15 May and 17
June from the five genotypes was 16,120 larvae.
FAW larvae were collected 7 and 12 days post-infestation in order to sample
parasitism of early and late larval instars. A total of 14 FAW parasitoid species was
collected in 1991 (Table 2). Cotesia marginiventris (Cresson) was the most dominant
parasitoid of the FAW recovered at 7 days from the first planting (Table 3). C. mar-
giniventris and Aleiodes (=Rogas) laphygmae (Gahan) were the most abundant
parasitoids of larvae collected 7 days post-infestation, while Archytas marmoratus
(Townsend) and Ophion flavidus Brull6 were the dominant parasitoids recovered 12
days after FAW infestation. Significantly more 0. flavidus than A. marmoratus were
collected at 12 days. Additional parasitoid species collected from the first planting were:
Meteorus autographae Muesebeck, Winthemia rufopicta (Bigot), Euplectrus platy-
hypenae Howard, Campoletis sonorensis (Cameron), and Lespesia archippivora
(Riley).
The most abundant FAW parasitoid that was collected from the second planting at
both 7 and 12 days was A. laphygmae (Table 3). A total of 1299 A. laphygmae emerged
from the larvae recovered from this planting. A. marmoratus was the second most
prevalent parasitoid from this planting (443), followed by 0. flavidus (329) and C.
marginiventris (391). However, C. marginiventris was collected in significantly higher
numbers at 7 days than A. marmoratus. At 12 days, both A. marmoratus and 0.
flavidus were collected in significantly higher numbers than C. marginiventris. Addi-
tional minor parasitoids, which had not been found in larvae from the first planting,
were: Homolobus truncator (Say), Trichomalopsis viridescens (Walsh), Isdromas
lycaenae (Howard), Spilochalcis hirtifemora (Ashmead), and Mesochorus disceitergus
(Say).
A. marmoratus was the most dominant parasitoid (711 individuals) of FAW larvae
recovered at both 7 and 12 days from the third planting (Table 3). The second most
prevalent parasitoid from this planting was 0. flavidus (418). There were significantly
more O. flavidus than A. laphygmae at 12 days, but not at 7 days. In contrast to the
collections from the other plantings, more 0. flavidus emerged from FAW collected 7
days post-infestation (257) than from larvae collected 12 days after infestation (161).
Although the largest number of FAW (5,758) was recovered from the seven and
twelve day collections after the fourth planting (Table 1), larvae collected from this
planting yielded the lowest total number of parasitoids (862) (Table 3). A. marmoratus
was significantly more abundant at 7 days than any of the other parasitoids. 0. flavidus
was the most abundant FAW parasitoid species (175 individuals recovered) at 12 days
for this planting (Table 3). Overall, 0. flavidus was the most abundant parasitoid col-


294


June, 1993












Fall Armyworm '92: Riggin et al.


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Florida Entomologist 76(2)


TABLE 2. PARASITOID SPECIES REARED FROM FALL ARMYWORM LARVAE COL-
LECTED FROM FIVE CORN GENOTYPES.

DIPTERA
Tachinidae
Archytas marmoratus (Townsend)
Lespesia archippivora (Riley)
Winthemia rufopicta (Bigot)

HYMENOPTERA
Braconidae
Aleiodes (=Rogas) laphygmae (Gahan)
Cotesia marginiventris (Cresson)
Homolobus truncator (Say)
Meteorus autographae Muesebeck
Chalcididae
Spilochalsis hirtifemora (Ashmead)
Eulophidae
Euplectrus plathypenae Howard
Ichneumonidae
Campoletis sonorensis (Cameron)
Isdromas lycaenae (Howard)
Mesochorus disceitergus (Say)
Ophion flavidus Brull6
Pteromalidae
Trichomalopsis viridescens (Walsh)



elected for the fourth planting (291). The second most prevalent parasitoid species from
this fourth planting was A. marmoratus (234). There was a higher number (48) of the
minor parasitoid H. truncator recovered from the FAW collected from this planting
than from the first three plantings.
A total of 6,139 parasitoids was recovered from FAW larvae collected from the four
corn plantings in 1991 (Table 4). The percent parasitism was 38.08% for all FAW larvae
collected. Larvae recovered from the resistant genotype MpSWCB-4 had the highest
percent parasitism (44.28%), while FAW collected from the susceptible genotype
Pioneer 3192 had the lowest parasitization level (31.70%). It appeared that in the'first
two plantings cultivars affected parasitism, but cultivars did not influence parasitism
in the latter two plantings. The most dominant parasitoid for the eight collections was
A. laphygmae which parasitized 12.78% of the recovered FAW. A. marmoratus
emerged from 10.01% of the FAW larvae, while 0. flavidus and C. marginiventris
parasitized 7.89% and 6.34%, respectively, of the FAW that were collected (Table 4).
H. truncator, W. rufopicta and M. autographae were the most prevalent of the minor
parasitoids, with parasitism rates that ranged from 0.22 to 0.35% (Table 4).

DISCUSSION

The fact that fewer FAW larvae were recovered from the genotypes MpSWCB-4
and Pioneer X304C (Table 1) is consistent with previous reports that corn genotypes
exhibiting resistance inhibit establishment of neonate larvae (Wiseman et al. 1983,
Isenhour et al. 1985). Although fewer FAW were recovered from these resistant


June, 1993


296












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300 Florida Entomologist 76(2) June, 1993

genotypes, the percent parasitism of these larvae was very high (Table 4). This indicates
that the factors conferring resistance to MpSWCB-4 and Pioneer X304C do not affect
the development of the parasitoids adversely. In a similar study, Pair et al. (1986b) also
found that there were significantly higher levels of parasitism when FAW larvae were
collected from Pioneer X304C than when they were collected from susceptible
genotypes. The fact that the development of C. marginiventris was not inhibited when
FAW were reared on diet containing MpSWCB-4 foliage (Riggin et al. 1992a), also
indicates that parasitoids are not harmed by the resistance factors of this genotype.
The present study indicates that the distribution of FAW parasitoids varies during
the growing season. Larvae were collected between 15 May and 17 June 1991. The most
prevalent parasitoid species was different for each of the combined FAW collections
from the four plantings during this one-month period. C. marginiventris was the most
prevalent parasitoid species collected from the first planting on 15 and 20 May (Table
3). The most prevalent parasitoids from the combined collections from the second, third,
and fourth plantings were A. laphygmae, A. marmoratus, and O. flavidus, respectively
(Table 3). These results are similar to those obtained in the same location in 1990, when
C. marginiventris was the dominant parasitoid of FAW on corn in mid-May, parasitizing
34% of the recovered larvae (Riggin et al. 1992b). In collections from subsequent plant-
ings in 1990, major parasitoids were: A. laphygmae (5 June collection), Chelonus in-
sularis Cresson (7 August), and A. marmoratus (23 August).
In a series of FAW parasitoid survey studies made in the southeastern USA during
the past ten years, various species have been shown to be the most dominant at different
times and in different locations. These parasitoids include: 0. flavidus (Rohlfs & Mack
1985, Pair et al. 1986a), C. sonorensis and C. marginiventris (Pair et al. 1986a), A.
marmoratus (Pair et al. 1986a), and C. insularis and C. marginiventris (Ashley et al.
1982). These past surveys, and the results presented in this paper, indicate that the
most efficient biological control programs for FAW will be ones that use and amplify
several parasitoids rather than programs that rely on an individual parasitoid species.

ACKNOWLEDGMENTS

We thank Kris Braman and Dave Buntin for critical reading of the manuscript, Max
Bass of the Coastal Plain Experiment Station, University of Georgia, Tifton, Georgia
for providing generous support throughout this project, Richard Layton and B. G.
Mullinix for their statistical advice, H. R. Gross, Jr. of the USDA, Tifton, Georgia, R.
W. Matthews of the University of Georgia, Athens, Georgia and E. E. Grissell, P. M.
Marsh, R. W. Carlson and M. E. Schauff of the USDA-ARS Systematic Entomology
Laboratory, Beltsville, Maryland for their aid in taxonomic identification, and M. Black,
P. Goodman, D. Atkins, J. Skinner, C. Mullis, N. Chalfant, K. A. Fitzgerald, and A.
C. Barrios for their technical assistance. This work was supported, in part, by a Grant-
in-Aid of Research from Sigma Xi, The Scientific Research Society, a grant from
Pioneer Hi-Bred International, Inc. and by HATCH projects no. 446 and 610 allocated
to The Georgia Agricultural Experiment Station.

REFERENCES CITED

ADKISSON, P. L., AND V. A. DYCK. 1980. Resistant varieties in pest management
systems, p. 233-273 in F. G. Maxwell and P. R. Jennings [eds.], Breeding plants
resistant to insects. Wiley, New York.
ASHLEY, T. R. 1979. Classification and distribution of fall armyworm parasites. Florida
Entomol. 62: 114-123.
ASHLEY, T. R., C. S. BARFIELD, V. H. WADDILL, AND E. R. MITCHELL. 1983.










Fall Armyworm '92: Riggin et al.


Parasitization of fall armyworm larvae on volunteer corn, bermudagrass, and
paragrass. Florida Entomol. 62: 267-271.
ASHLEY, T. R., E. R. MITCHELL, N. C. LEPPLA, AND E. E. GRISSEL. 1980. Parasites
attacking fall armyworm larvae, Spodopterafrugiperda in late planted field corn.
Florida Entomol. 63: 136-142.
ASHLEY, T. R., V. H. WADDILL, E. R. MITCHELL, AND J. RYE. 1982. Impact of
native parasites on the fall armyworm, Spodopterafrugiperda (Lepidoptera: Noc-
tuidae) in south Florida and release of the exotic parasite, Eiphosoma vitticole
(Hymenoptera: Ichneumonidae). Environ. Entomol. 11: 833-837.
GROSS, H. R., AND S. D. PAIR. 1991. Seasonal distribution, response to host develop-
mental stage, and screened-cage performance ofArchytas marmoratus (Diptera:
Tachinidae) and Ophion flavidus (Hymenoptera: Ichneumonidae) on Spodoptera
frugiperda (Lepidoptera: Noctuidae). Florida Entomol. 74: 237-245.
GROSS, H. R., J. R. YOUNG, AND B. R. WISEMAN. 1982. Relative susceptibility of a
summer-planted dent and tropical flint corn variety to whorl stage damage by
the fall armyworm (Lepidoptera: Noctuidae). J. Econ. Entomol. 75: 1153-1156.
ISENHOUR, D. J., B. R. WISEMAN, AND N. W. WIDSTROM. 1985. Fall armyworm
(Lepidoptera: Noctuidae) feeding responses on corn foliage and foliage/artificial
diet medium mixtures at different temperatures. J. Econ. Entomol. 78: 328-332.
ISENHOUR, D. J., AND B. R. WISEMAN. 1987. Foliage consumption and development
of the fall armyworm as affected by the interactions of a parasitoid, Campoletis
sonorensis and resistant corn genotypes. Environ. Entomol. 16: 1181-1184.
MITCHELL, E. R., V. H. WADDILL, AND T. R. ASHLEY. 1984. Population dynamics
of the fall armyworm (Lepidoptera: Noctuidae) and larval parasites on whorl
stage corn in pheromone-permeated field environments. Environ. Entomol. 13:
1618-1623.
ORR, D. B., AND D. J. BOETHEL. 1986. Influence of plant antibiosis through four
trophic levels. Oecologia 70: 242-249.
PAIR, S. D., J. R. RAULSTON, A. N. SPARKS, AND P. B. MARTIN. 1986a. Fall ar-
myworm (Lepidoptera: Noctuidae) parasitoids: differential spring distribution
and incidence on corn and sorghum in the southern United States and northeast-
ern Mexico. Environ. Entomol. 15: 342-348.
PAIR, S. D. B. R. WISEMAN, AND A. N. SPARKS. 1986b. Influence of four corn
cultivars on fall armyworm (Lepidoptera: Noctuidae) establishment and parasiti-
zation. Florida Entomol. 69: 566-570.
PRICE, P. W., C. E. BOUTON, P. GROSS, B. A. MCPHERON, J. N. THOMPSON, AND
A. E. WEIS. 1980. Interactions among three trophic levels: influence of plants
on interaction between insect herbivores and natural enemies. Annu. Rev. Ecol.
Syst. 11: 41-65.
RIGGIN, T. M., D. J. ISENHOUR, AND K. E. ESPELIE. 1992a. Effect on Cotesia mar-
giniventris (Hymenoptera: Braconidae) when rearing host fall armyworm
(Lepidoptera: Noctuidae) on meridic diet containing foliage from resistant or
susceptible corn genotypes. Environ. Entomol. 21: 214-219.
RIGGIN,T. M., B. R. WISEMAN, D. J. ISENHOUR, AND K. E. ESPELIE. 1992b. Inci-
dence of fall armyworm (Lepidoptera: Noctuidae) parasitoids on resistant and
susceptible corn genotypes. Environ. Entomol. 21: 888-895.
ROHLFS, W. M., III, AND T. P. MACK. 1985. Seasonal parasitism rates, host size, and
adult emergence pattern of parasitoids of the fall armyworm, Spodoptera
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era: Ichneumonidae). Ann. Entomol. Soc. Am. 78: 217-220.
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SPARKS, A. N. 1986. Fall armyworm (Lepidoptera: Noctuidae): potential for area-wide
management. Florida Entomol. 69: 603-614.
WALLER, R. A., AND D. B. DUNCAN. 1969. A Bayes rule for the symmetric multiple
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WISEMAN, B. R., F. M. DAVIS, AND J. E. CAMPBELL. 1980a. Mechanical infestation
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425-432.
WISEMAN, B. R., B. G. MULLINIX, AND P. B. MARTIN. 1980b. Insect resistance
evaluations: effect of cultivar position and time of rating. J. Econ. Entomol. 73:
454-457.
WISEMAN, B. R., F. M. DAVIS, AND W. P. WILLIAMS. 1983. Fall armyworm: larval
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WISEMAN, B,. R., W. P. WILLIAMS, AND F. M. DAVIS. 1981. Fall armyworm resist-
ance mechanisms in selected corns. J. Econ. Entomol. 74: 622-624.




EFFECT OF CORN FOLIAR CUTICULAR LIPIDS ON THE
MOVEMENT OF FALL ARMYWORM (LEPIDOPTERA:
NOCTUIDAE) NEONATE LARVAE

GUANG YANG,1,2 KARL E. ESPELIE,' B. R. WISEMAN,3 AND DAVIDJ. ISENHOUR2,4
'Department of Entomology, University of Georgia
Athens, GA 30602

2Department of Entomology, Coastal Plain Experiment Station
University of Georgia
Tifton, GA 31793

8USDA-IBPMRL
P. O. Box 748
Tifton, GA 31793

4Current Address: Pioneer Hi-Bred International, Inc.
Department of Research Specialists, Johnston, IA 50131.

ABSTRACT

Genotypes of corn known to vary in their resistance to fall armyworm (FAW),
Spodoptera frugiperda (J. E. Smith), were utilized in a study designed to examine the
plant resistance role of surface ultrastructure and cuticular lipids. Scanning electron
microscopy showed dramatic differences between the ultrastructural appearance of
lower (4th) and upper (8th) leaves of the resistant MpSWCB-4 and the susceptible
Cacahuacintle X's. In a choice test, FAW larvae preferred the upper leaves from which
the cuticular lipids had been removed over untreated leaves of these two genotypes.
Larval behavior was monitored by video camera on the adaxial and abaxial surfaces of
upper and lower leaves of MpSWCB-4 and Cacahuacintle X's and on foliage samples
with and without cuticular lipids. FAW showed more nonacceptance behavior on the
untreated foliage than on the chloroform-extracted foliage. FAW larvae traveled


302









Fall Armyworm '92: Yang et al.


greater distances and crawled faster when they were on upper leaves rather than lower
leaves and when they were on the abaxial leaf surface rather than the adaxial surface.
However, no difference in behavior was found when larval movement was monitored
on the cuticular lipid extracts from the foliage of two resistant and two susceptible corn
genotypes.

RESUME

En un studio disefado para examiner el papel de los lipidos cuticulares y la estruc-
tura de la superficie cuticular, se utilizaron genotipos de maiz con variabilidad en resis-
tencia a el cogollero del maiz (FAW), Spodoptera frugiperda (J. E. Smith). Usando
electromicroscopia se pudieron observer diferencias significativas entire la apariencia
ultraestructural de hojas bajas (4ta) y altas (8ava)de la variedad resitente MpSWCB-4
y la susceptible Cacahuacintle X's. En una prueba de preferencia, las larvas de FAW
prefirieron las hojas altas en las que se habia removido los lipidos cuticulares sobre hojas
no tratadas de los dos genotipos. Con ayuda de una camera video se observe el compor-
tamiento larvario en el haz y enves de las hojas con y sin lipidos cuticulares. FAW
mostro mas aceptaci6n del follaje no tratado que del extract con cloroformo del follaje.
La larva de FAW recorri6 distancias mas grandes y se movi6 mas rdpidamente cuando
estaba en las altas que cuando estaba en las hojas bajas y se movi6 mas cuando estaba
en el env6s que en el haz. No se observaron diferencias en comportamiento en
movimiento de larvas en los extractos de lipidos cuticulares del follaje de dos genotipos
resistentes y dos susceptibles.




The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is a serious de-
foliating pest of corn, sorghum, peanut and other crops in North and Central America.
The larvae usually hide in and feed on the whorl tissue of corn plants at the whorl stage
and cause severe damage to the host plants (Sparks 1986).
The development of corn plants which are resistant to attack by FAW larvae is an
economically and environmentally desirable method to control this pest (Painter 1968,
Williams et al. 1983). The identification of sources of resistance in corn to FAW is an
essential aspect in the development of a successful plant resistance program. Several
corn genotypes have been reported to be resistant to FAW (Wiseman & Davis 1979,
Wiseman et al. 1981, 1983, Isenhour et al. 1985), but the behavior of larvae related to
the mechanisms of resistance are not well understood. Identification of the bases for
resistance in corn plants to FAW would allow for the more efficient incorporation of
these characteristics into corn breeding programs.
The plant surface, with which an insect pest first comes in contact, plays an integral
role in insect/plant interactions (Woodhead & Chapman 1986). Many herbivorous insects
seem to be attracted to their potential host plants by visual, olfactory or tactile stimula-
tive cues based on the physical and chemical characteristics of the plant surface (Chap-
man 1977, Stadler 1986). The chemical and ultrastructural characteristics of plant cuticu-
lar lipids can affect many aspects of insect behavior, such as orientation, movement,
oviposition and feeding (Bernays et al. 1976, Chapman & Bernays 1989, Espelie et al.
1991). Variations in the chemical composition and ultrastructure of plant cuticular lipids
may result in variable plant resistance to insect attack (Klingauf et al. 1978, Woodhead
1983, Yang et al. 1992). If the insects do not like the plant surface, they may exhibit
nonacceptance behavior and move away from that surface (Widstrom et al. 1979, Ber-
nays et al. 1985, Stoner 1990, Eigenbrode et al. 1991). In the present paper, we examine
the role that ultrastructure and cuticular lipids of corn foliage may play in resistance to
FAW by affecting neonate larval movement on the leaf surface.


303









Florida Entomologist 76(2)


MATERIALS AND METHODS

Plant Material

Two FAW resistant corn genotypes, MpSWCB-4 and Pioneer X304C, and two FAW
susceptible genotypes, Cacahuacintle X's and Pioneer 3192 (Scott & Davis 1981, Wise-
man et al. 1980, Gross et al. 1982), were planted in April 1991 in Tifton, Georgia, using
agronomic practices common to the area. No soil or foliar insecticides were utilized.
Forty-five days after planting, when the plants were at the mid-whorl stage, plants of
each corn genotype were cut at the stem bases, placed in plastic bags, immediately
transported to the laboratory and stored at 4C. Lower (4th from the plant base) and
upper (8th) leaves were collected from each plant. FAW neonate larvae were obtained
from a colony maintained at the Coastal Plain Experiment Station, Tifton, Georgia.

Scanning Electron Microscopy

The 4th and 8th leaves of genotypes MpSWCB-4 and Cacahuacintle X's were cut
into small pieces (0.6 x 0.6 cm), fixed over night in 2% glutaraldehyde in 0.2M cacody-
late, washed in 0.1M cacodylate buffer with 5% sucrose for 2-3 min, post-fixed in 1%
osmium tetroxide for 1 hr, washed again in 0.1M cacodylate buffer with 5% sucrose,
dehydrated sequentially in 30%, 50%, 70%, 80%, 95% and 100% ethanol (each for 10
min), rinsed twice in 100% ethanol, and critical-point dried. Samples were then mounted
on aluminum stubs with double sticky tape and silver paint, coated with gold-palladium
(40 nm thickness) with a Hummer X Sputter Coater, and examined with a Phillips 505
Scanning Electron Microscope located at the Center for Advanced Ultrastructure Re-
search, University of Georgia, Athens, Georgia. Both the adaxial (upper leaf surface)
and the abaxial (lower surface) sides of the leaves were examined.

FAW Preference Bioassays

The 4th and 8th fresh leaves of the four corn genotypes were separated into two
equal portions. One portion was dipped in chloroform for 1 min at room temperature to
remove the cuticular lipids and air-dried in a flow hood for 30 min. The other leaf portion
was untreated. Both the extracted and the unextracted leaves were cut into segments
(5 cm in length). An extracted leaf segment and an unextracted leaf segment were
placed on opposite sides of a plastic petri dish (20 cm diam.). Twenty FAW neonate
larvae were placed in the center of the petri dish. Two water-saturated cotton balls
were placed on opposite sides of the petri dish to maintain high humidity. The petri
dishes were transferred to a dark chamber and kept at 250C. The number of larvae on
each leaf segment was recorded 2 hr and 24 hr after addition of the larvae. Each
treatment was replicated 10 times, and treatment means were separated by the Stu-
dent's t test (Ott 1988).

Movement of FAW Larvae on Leaf Surfaces

Leaves of MpSWCB-4 and Cacahuacintle X's were separated into two portions and
either extracted with chloroform or left untreated, as described above. The leaves were
cut into segments (4 cm long) which were clamped between two hard paper discs. One
of these discs had a circular hole (2.5 cm diam.) in the center. A thin barrier of petroleum
jelly was applied around the outer edge of this test arena to prevent larval escape. A
newly hatched FAW larva was placed on the leaf surface in the center of the test arena
and larval behavior was recorded with a video camera for 5 min (Varela & Bernays


June, 1993









Fall Armyworm '92: Yang et al.


1988). Lights were balanced to avoid bias of larval phototaxis. The distance the larva
moved was measured with a map-wheel (Varela & Bernays 1988), and the time spent
crawling, the time spent searching, the crawling speed of the larvae, and the number
of times that searching behavior occurred were also recorded (Eigenbrode et al. 1991).
Crawling speed was defined as the total distance traveled divided by the time that the
larva spent in crawling. Searching was defined as raising the front half of the body from
the substrate and moving it from side to side more than once. Both adaxial and abaxial
surfaces of extracted and unextracted foliage of 4th and 8th leaves of MpSWCB-4 and
Cacahuacintle X's were tested. A filter paper surface was tested as a control. The
experiment was designed as a 4-factor factorial experiment, each factor with 2 levels
(2 x 2 x 2 x 2) with 10 replicates in each cell. The treatment means were separated by
either the ANOVA of a factorial experiment, Least Significant Difference (LSD) or
Student's t test, as appropriate (Ott 1988).

Movement of FAW Larvae on Leaf Extracts

Lower (4th) and upper (8th) fresh leaves (100 g each) of the four corn genotypes
were extracted in chloroform (300 ml) for 1 min at room temperature. Extracts were
condensed to 5 ml with a rotary evaporator, and stored in a freezer at -20C. Aliquots
(0.1 ml) of these extracts, which were equivalent to the amount from 2 g fresh leaf
tissue, were applied to the surface of a glass petri dish (6 cm diam.) and air-dried for 1
hr. An equal amount of chloroform was applied to a glass petri dish to serve as a solvent
control. A hard paper disc with a circular hole (3.5 cm diam.) in the center was placed
over the treated surface. A FAW neonate was placed in the center of the test arena
and video-taped for 5 min. Larval behavior was monitored as described above. Each
treatment was replicated 10 times. The data were analyzed by ANOVA and the treat-
ment means were separated by the Least Significant Difference method (Ott 1988).

RESULTS

Ultrastructure of Corn Leaf Surfaces

The adaxial and abaxial surfaces of lower (4th) and upper (8th) corn leaves from
MpSWCB-4 and Cacahuacintle X's were examined by scanning electron microscopy.
The ultrastructural appearance of the foliar surfaces of these two genotypes were very
similar. However, there were dramatic differences between the lower and upper leaves
and between the adaxial and abaxial surfaces of the upper leaves in both genotypes.
Large trichomes and small spines were present on the adaxial surface of the upper
leaves in both corn genotypes (Figure 1A). These trichomes and spines were not found
on the abaxial surface of the upper leaves or on either side of the lower leaves. At higher
magnification the wax layer on the adaxial surface (Figure 1B) and abaxial surface of
the upper leaves in both corn genotypes exhibited an amorphous appearance. There
was a dense array of crystals on the adaxial surface of the lower leaves of both
MpSWCB-4 and Cacahuacintle X's (Figure 1C). At higher magnification this wax layer
appeared to be composed of ribbon-shaped crystals (Figure 1D). The abaxial surface of
the lower leaves from both genotypes had an appearance very similar to that of the
adaxial surface.

FAW Larval Preference for Unextracted or Extracted Corn Foliage

FAW larvae showed a significant preference for extracted over unextracted upper
leaves from MpSWCB-4 and Cacahuacintle X's and for extracted over unextracted


305









Florida Entomologist 76(2)


June, 1993


Fig.1. Scanning electron micrographs of leaves of corn genotype MpSWCB-4: A)
adaxial surface of upper (8th) leaf with large trichomes and small spines; B) adaxial
surface of upper (8th) leaf; C) adaxial surface of lower (4th) leaf; D) adaxial surface of
lower (4th) leaf.



lower leaves from Pioneer X304C after both 2 and 24 hours (Table 1). In the remaining
treatments, there were no cases where the larvae exhibited a significant preference for
foliage either with, or without, the cuticular lipids.

FAW Movement on Corn Leaves and Extracted Corn Leaves

FAW larvae traveled a significantly greater distance on the abaxial surface of unex-
tracted MpSWCB-4 upper leaves than they did on the abaxial surface of lower leaves
of this genotype (Table 2). FAW larvae traveled significantly farther when they were
on the abaxial surface of upper unextracted leaves than on the adaxial surface of lower
leaves, and on the abaxial surface of upper extracted leaves than on the adaxial surface
of both upper and lower extracted foliage of Cacahuacintle X's.
In most cases, FAW larvae moved significantly faster on the abaxial surface of
upper leaves than they did when they were on the adaxial surface of lower leaves (Table


0-.-- m W




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