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Title: Pepper weevil and sweetpotato whitefly management on pepper
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Permanent Link: http://ufdc.ufl.edu/UF00065229/00001
 Material Information
Title: Pepper weevil and sweetpotato whitefly management on pepper
Series Title: Bradenton GCREC research report
Physical Description: 9 leaves : ; 28 cm.
Language: English
Creator: Schuster, David J
Gulf Coast Research and Education Center (Bradenton, Fla.)
Publisher: Gulf Coast Research and Education Center, IFAS, University of Florida
Place of Publication: Bradenton FL
Publication Date: 1988
 Subjects
Subject: Peppers -- Diseases and pests -- Control -- Florida   ( lcsh )
Sweetpotato whitefly -- Control -- Florida   ( lcsh )
Pepper weevil -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaf 6).
Statement of Responsibility: David J. Schuster ... et al.
General Note: Caption title.
General Note: "October, 1988"
 Record Information
Bibliographic ID: UF00065229
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 63682136

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




/00



f/C Cenirai Sccilce
GULF COAST RESEARCH AND EDUCATION CENlftrar1
IFAS/UNIVERSITY OF FLORIDA
5007 60TH STREET EAST NOV 18 1983
BRADENTON, FL 34203
University of Florida
Bradenton GCREC Research Report BRA1988-19 ~' -e----- "e-1988

PEPPER WEEVIL AND SWEETPOTATO WHITEFLY MANAGEMENT ON PEPPER

David J. Schuster, David Riley, James F. Price
and James B. Kring1

Recent research at the Gulf Coast Research & Education Center (GCREC) has
focused on two insect pests threatening pepper production in Florida: the
pepper weevil (Anthonomus eugenii Cano) and the sweetpotato whitefly
[Bemisia tabaci (Gennadius)]. The former has been an intermittent pest in
Florida since the mid 1930s and the latter has been observed in Florida
since the late 1800s, but has only been considered a pest in the state
since 1986 (Price 1987).

PEPPER WEEVIL
Adult pepper weevils are about 1/8 inch long, brown to black beetles with
long snouts. The female pepper weevil can lay over 300 eggs in her
lifetime (Elmore et al. 1934) with an average of 7 ovipositions per day
(Wilson 1986). Eggs are usually laids in flowers and small fruit but may
also be laid in larger fruit and even in leaf petioles (Schuster 1986).
Eggs hatch in 3-5 days, depending upon temperature (Elmore et al. 1934),
and the resulting small, grub-like larvae complete their development and
pupate within the infested plant parts. The average total generation time
is about 3 weeks.
Infested flowers and fruit often fall; however, pepper weevil larvae can
still complete their development if fallen plant parts do not dry (Wilson
1986). An accumulation of fallen flowers and fruit is often the first
indication of a pepper weevil infestation.
Wilson (1986) observed oviposition and larval development only in plants
from the genera, Capsicum (4 species including pepper) and Solanum
(including eggplant, horse-nettle, Jerusalem cherry and 3 species of
nightshade). Fruit of American and eastern black nightshades were equally
suitable for larval development as were tabasco and bell pepper (Wilson
1986). Furthermore, populations of the pepper weevil were able to
oversummer on nightshade on the perimeters of fields previously planted to
pepper (Patrock and Schuster 1987).

1Professor of Entomology, Graduate Assistant, Associate Professor of
Entomology, and Adjunct Professor of Entomology, respectively.








Cultural and Insecticidal Control

There are several cultural manipulations that can be utilized to aid in
the management of the pepper weevil. Since nightshade is a suitable host
of the weevil and since the weevil can oversummer on this host plant,
management of these weeds on the perimeters of fields would be definitely
advantageous. Because adult weevils can live for relatively long periods,
nightshade management should be initiated at least a month prior to
planting. If nightshade plants are killed too soon before or anytime
after transplanting, adult weevils may disperse to pepper plantings.

Transplanting weevil-free plants is an important early step in managing
this pest. Disposal of cull fruit near planted fields should be avoided
since pepper weevil larvae can complete development in fruit that have
dropped from the plants. If it is necessary to dispose of such fruit near
pepper fields, they should be buried under water or soil. Following the
last harvest, fields should be disked and any remaining nightshade plants
should be destroyed to reduce chances of infesting later crops.

There are currently 4 insecticides registered for pepper weevil control on
pepper (Table 1). All are reasonably effective but each has limitations.
Kryocide, when applied as a spray at 8.0 lb ai/100 gal, has sometimes
reduced overall yield (Schuster and Everett 1982). Asana XL and
Ambush/Pounce have restrictions on the amount of active ingredient that
can be applied per acre per season and Vydate and Asana XL can only be
applied up to 7 days before harvest. Only Asana XL can be applied to
non-bell peppers and then can only be applied on a 7-10 day schedule.

In a recent trial on bell peppers, the numbers of adult weevils were
counted 1, 2, 3 and 5 days following the last of nine weekly applications
of Vydate and Pydrin (a formerly used product replaced by Asana XL). No
reduction in the number of adults was observed with Pydrin (Table 2).
Fewer adults were observed on plants sprayed with Vydate6 for two days
after the application. This trial was adjacent to a one acre plot of bell
pepper that was heavily infested and probably served as a source of adults
to move into the experimental field. Thus, under severe weevil pressure,
Vydate would need to be applied on a three-day schedule.
Since the spring of 1987, a series of field trials concerning pepper
weevil has been conducted at the GCREC and on various farm sites. The
overall objectives of these trials have been to refine sampling techniques
for detecting damaging population levels of pepper weevil in the field and
to use these sampling techniques to guide pest management practices, in
particular to implement the use of action thresholds for insecticide
applications. As many growers are aware, the pepper weevil adult is quite
difficult to detect early in the pepper growing season until buds or fruit
fall. Also, once fallen fruit are detected, the pepper weevils developing
within the fruit are difficult to control with insecticides. It would be
more advantageous to detect the problem earlier, prevent the initial
oviposition, and reduce the fallen buds.

The current scouting method, inspections of at least 100 terminal buds
per acre for pepper weevil adults, has been shown to detect the pepper
weevil population 1-2 weeks after an infestation has occurred. Therefore,








once weevil adults are detected, the next generation is already present.
This is one reason why pepper weevil infestations may seem to have
appeared so suddenly. The limitations of present detection methods leave
us with two management alternatives. One is to apply insecticides
preventively and the other is to develop a more sensitive sampling
technique.

Spraying preventively does take care of the immediate problem, but may
lead to the development of insecticide resistance and may also suppress
some of the natural enemies of the pepper weevil. In the spring of 1988,
over 50% parasitism of pepper weevil grubs was found in fallen Jalapeno
buds and over 20Z. in fallen bell buds. The parasite was Cactolaccus
hunterii, a pteromalid wasp, and has been found for several years at the
GCREC. Very few parasites have been found on pepper weevil larvae in
larger fallen fruit (which may offer some form of physical protection from
the wasp) meaning that, later in the season, parasitism will probably have
much less impact on pepper weevils.

Another consideration with preventive spraying is knowing when to begin
spraying, or knowing if spraying is even necessary. For two seasons, the
rate of increase of pepper weevil adults in untreated fields has remained
relatively low (<10% per day) early in the season compared to the rate of
increase later in the season (>50% per day). Thus, when the pepper weevil
is present, early season problems have not been severe; rather, it is the
anticipation of successive generations of pepper weevil that makes early
season control important.

Another factor which determines when to begin insecticide applications is
the location and movement of pepper weevils from wild hosts, particularly
from nightshade, or from abandoned pepper fields into new pepper fields.
In February of 1988, marked pepper weevil adults were released and
monitored in an old bell pepper field. Not until 2 weeks later were the
marked adults detected approximately 300 ft. from the point of release.
Thus, adults do not appear to disperse rapidly and a rigorous sanitation
control program may reduce the need for pepper weevil control in isolated
fields. This makes it important to be able to detect incipient
populations of pepper weevil on a field by field basis rather than
regionally in order to guide the pest management strategy.

This leads to the second alternative, to develop a more sensitive sampling
technique. After 2 seasons of field experimentation, the terminal bud
inspection in the morning still remains the most cost effective in terms
of time spent and pepper weevil adults encountered. However, afternoon
samples using the same technique yielded about 1/2 as many pepper weevil
because pepper weevil adults seek the unexposed areas of the plant in the
afternoon. Recognizing this, a 50% lower threshold for the afternoon
will be evaluated this fall.

An alternative method for detecting pepper weevil populations in pepper
fields is also currently being tested. In ilarch 1988, a set of 28 sticky
traps was placed in approximately 1/2 acre each of Jalapeno and bell
peppers. In this same field, several different visual scouting techniques
and an absolute sample were employed. The total number of pepper weevil
adults captured on sticky cards for the first three weeks was 11, while








for all other sampling methods combined, only 3 adults were counted. Even
with this large number of sticky traps, only a small fraction of the
total scouting time was required to check the traps compared to the
visual inspection of plants.

With these promising results, another set of experiments was conducted at
the end of the season when the pepper weevil population level was high.
The four major factors that were investigated were color of traps, height
of traps, band width of traps, and the time of day for inspection of
traps. The results indicate that the most attractive color for the traps
is white, the best band width tested is 15 cm, and the best time of day to
check the traps is in the late afternoon or early morning (Table 3). The
morning traps were exposed for 12+ hours while the late afternoon traps
were exposed only 2 hours, so late afternoon may be better. The best trap
height is from 10-50 cm (Table 4).

SWEETPOTATO WJHITEFLY

Sweetpotato whitefly adults are small insects about 1/32 inch long with
pale yellow bodies and white wings. They resemble small flies but are
more closely related to aphids since they have piercing-sucking
mouthparts. Adults prefer the younger leaves and deposit minute,
cigar-shaped eggs on the lower surfaces of these leaves. The immature
stages are usually called nymphs and also have piercing-sucking
mouthparts. The newly hatched nymphs have well-developed legs and are the
only mobile nymphs. After finding a suitable feeding site on the lower
leaf surface, these "crawlers" attach to the undersurfaces of leaves to
begin feeding and usually do not move again. The subsequent three nymphal
stages appear as flattened, oval scales. The final immature stage (resting
or pupal stage) is more convex and elliptical and has large, conspicuous
red eyes (Lopez-Avila 1986). The development time from egg to adult at 80
F is about 3 weeks (Coudriet et al. 1985). Because of the delay between
the time of egg deposition and the completion of development, the immature
stages (particularly the pupal stage) may be found on lower, older leaves,
especially on rapidly growing plants (Ohnesorge et al. 1980).

Nymphal and adult whiteflies damage plants by sucking their sap.
Chlorotic spots may appear on the upper leaf surfaces and affected plants
may become unthrifty. !Jhitefly feeding produces honeydew upon which sooty
mold can grow. Heavy populations of the sweetpotato whitefly have been
associated recently with irregular ripening of tomato fruit, but no such
problem was observed on heavily infested pepper. However, the
sweetpotato whitefly is a known vector of about 19 virus diseases
including tobacco leaf curl on pepper.

Fortunately, no pepper viruses are known to be transmitted by whiteflies
in Florida. However, viruses presently in weeds possibly could be
disseminated to crop plants or other whitefly-vectored viruses could be
imported into Florida. An unidentified virus on pepper has recently been
demonstrated to be vectored by B. tabaci in Mexico (Everett, personal
communication).
Insecticides have most often been used to manage the sweetpotato whitefly,
especially on cotton. Resistance to organophosphate and synthetic








pyrethroid insecticides has been reported in California (Prabhaker at al.
1985). The effectiveness of selected insecticides has been evaluated at
Bradenton on poinsettia both in the laboratory using lab-reared
sweetpotato whiteflies and in the greenhouse using a naturally occurring
population. Results to date indicate that, of insecticides currently
registered for use on peppers, Thiodan, Lindane, Ambush, Pounce, Asana XL,
and Pyrenone provide very good kill of whitefly adults in the laboratory
(Table 5). These same insecticides also gave adult control in the
greenhouse. Ambush, Pounce, Asana XL, Pyrenone, Safer's Soap, and Vydate
resulted in the most consistent reductions in the numbers of nymphs
surviving to adult emergence in the greenhouse. Thus, registered
insecticides are available for the management of this pest on pepper.
Growers who encounter this pest on pepper should alternate insecticides of
different chemical classes to reduce the potential for resistance.

Thorough coverage of under surfaces with insecticides is essential, since
all life stages of the whitefly occur on the undersides of foliage and
since eggs, nymphs (except crawlers) and pupae do not move and must be
impinged by contact insecticides. Since whiteflies are sucking pests,
only systemic insecticides are ingested. The only systemic insecticide
listed in Table 5 is Vydate.

Management of the sweetpotato whitefly must begin in the transplant
production facility and not in the field. Production facilities should be
located away from infested areas if possible and should be screened to
exclude invading adults. Employees should avoid wearing yellow clothing
or 'using yellow equipment since adults are attracted to yellow and would
be transported into production facilities on these items. Weeds should be
managed in advance of planting or transplanting in and around production
greenhouses and fields. aLew crops should not be planted near infested
crop and weed plants. After harvests, production fields should be treated
with an adulticide to reduce the number of dispersing adults, then should
be destroyed immediately with an approved, fast-acting herbicide.

UV reflective mulch (plastic film sprayed with aluminum paint) can be used
to repel alighting aphids, especially when plants are small, and reduce
the incidence of viruses they transmit. Our experiments also suggest that
the number of alighting adult whiteflies can also be reduced with such
mulch (Table 6).

REFERENCES CITED
Coudriet, D. L., N. Prabhaker, A. N. Kishabaz and D. E. rieyerdirk. 1905.
Variation in developmental rate on different hosts and overwintering
of the sweetpotato whitefly, Bemisia tabaci (Homoptera:Aleyrodidae).
Environ. Entomol. 14:516-519.
Elmore, J. C., A. C. Davis and R. E. Campbell. 1934. The pepper weevil.
USDA Tech. Bull. 447. U.S. Govt. Printing Office, Uashington, DC. 27 pp.

Lopez-Avila, A. 1986. Taxonomy and biology. In i .J.W. Cook, ed.,
Bemisia tabaci A literature survey on the cotton whitefly with an
annotated bibliography. C.A.B. Internat, Inst. Biol. Control, Silwood
Park, U.K. 121 pp.







6
Ohnesorge, B.. N. Sharaf, and T. Allawi. 1980. Population studies on the
tobacco whitefly Bemisia tabaci Genn. (Homoptera:Aleyrodidae) during the
winter season. I. The spatial distribution on some host plants.
Zeitschrift fur Angewandte Entomol. 90:226-232.

Patrock, R. J. and D. 3. Schuster. 1987. Field survey for the pepper
weevil, Anthonomus eugenii, on nightshade. Proc. Fla. State Hort. Soc.
100:217-220.

Prabhaker, N., D. L. Coudriet and D. E. Neyerdirk. 1985. Insecticide
resistance in the sweetpotato wvhitefly, Bemilsia tabaci
(Homoptera:Aleyrodidae). J. Econ. Entomol. 73:740-752.

Price, J. F. 1987. Controlling a "new" pest. Greenhouse Grower 5:70,
72-73.

Schuster, D. J. 1986. management of the pepper weevil. In U. ii. Stall,
ed., 1986 Florida Pepper Institute, Univ. of Fla., Veg. Crops Ext. Rept.
VEC86-3.

Schuster. D. 3. and P. H. Everett. 1982. Control of the beet armyworm
and pepper weevil on pepper. Proc. Fla. State Hort. Soc. 95:345-351.

Wilson, R. J. 1986. Observations on the behavior and host relations of
the pepper weevil Anthonomus eugenii Cano (Coleoptera:Curculionidae) in
Florida. PhD dissertation. Univ. of Fla., Gainesville, 94 pp.


Table 1. Insecticides registered
pepper.


for control of the pepper weevil on


Preharvest
Lb. a.i./ interval
Insecticide acre (days) Remarks

Ambush/Pounce 0.1-0.2 3 no more than 1.6 lb ai
per acre per season

Kryocide 25-50 0 Wash off residue

Asana XL 0.025-0.05 7 7-10 day spray interval
Ho more than 0.35 lb ai
per acre per season

Vydate 0.5-1.0 7 Spray as needed








Table 2. Control of adult pepper weevils on bell pepper with insecticides.


Lb. ai/ No. weevils/5 miI. search on the
Insecticide 100 gal. indicated day after application
1 2 3 5

Vydate 1.0 4.2 a 6.0 a 17.2 a 22.8 a

Pydrin 0.1 32.2 b 33.0 b -

Check 37.2 b 26.5 b 29.5 a 22.2 a









Table 3. Evaluation of the effects of trap color, band width and time of
day on the number of adult pepper weevils captured on sticky
traps.


Experiment Treatment Wo. adults

Color White 50
Yellow 24
Green 17
Blue 15
Black 15
Orange 13
Red 12

Band width 1 cm 1
3 cm 8
5 cm 18
7 cm 54
15 cm 107

Time of sample 7:00 am 110
9:00 am 48
11:00 am 49
1:00 pm 41
3:00 pm 28
5:00 pm 103








Table 4. Evaluation of trap height on the number
captured on sticky traps.


of pepper weevil adults


... adults trapped
Trap, height (cm Bell pepper. Jalapeno pepper

10 17 38
50 10 16
60 3 64
70 1 42
80 4 37
90 2 14







Table 5. Insecticides effective for control of the sweetpotato whitefly
life stages indicated and registered for use on pepper in
Florida.


Activity against
Insecticidal group Insecticide Adults Nymphs Pupae

Carbamate Vydate X

Synthetic pyrethroid(:') Asana X X
Ambush, Pounce X X
Natural pyrethrum Pyrenone X

Chlorinated Thiodan X
hydrocarbon Lindane X

Potassium salts of Safer Insecticidal
fatty acids Soap (**) X X


(*) The piperonyl butoxide
effectiveness of these


synergist, Butacide, slightly enhanced the
synthetic pyrethroids.


(**) Safer Insecticidal Soap has not been widely tested under Florida's
tomato production conditions.




WA


Table 6. Insect infestations and yield of peppers grown on various soil mulches. GCREC, 1987.


iHulch treatment

Aluminum paint

Aluminum film

White plastic

White paint

White paint + mica

lack plastic


10 leaves*

9.0 a0-

100.0 b

83.8 b

51.0 b

171.0 b

200.0 b


Aphids
50o.


uninfested
leaves

7.2 a

4.2 ab

2.8 bc

2.2 bc

2.0 bc

0.2 c


No. thrips/
10 flowers

2.8 a

4.0 ab

13.2 b

6.3 ab

12.2 ab

5.5 ab


No. whiteflies/
yellow dish
trap

1.0 a

3.0 ab

5.5 b

2.8 ab

4.0 b

4.2 b


Fruit yield/18 plants
,o. Ut. (lb.)

52.0 I3.S. 21.8 N.S.

42.0 17.2

48.0 20.9

39.2 15.3

43.2 16.4

11.8 4.6


"Transformed log10 (x + 1) prior to analysis. leans are presented in original scale.
**N.S. = not significant at P = 0.05. i-isans in columns followed by the same letter are not significantly
different at the P = 0.05 level, Duncan's multiple range test,


" -'


L--


MW




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