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Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: The pecan shuckworm
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027094/00001
 Material Information
Title: The pecan shuckworm
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 18 p. : ill. ; 23 cm.
Language: English
Creator: Walker, Fred W ( Fred Winter )
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1933
Copyright Date: 1933
 Subjects
Subject: Pecan -- Diseases and pests -- Florida   ( lcsh )
Laspeyresia   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 18).
Statement of Responsibility: by Fred W. Walker.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00027094
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AEN4724
oclc - 18204881
alephbibnum - 000924119

Table of Contents
    Front Cover
        Page 1
        Page 2
    Table of Contents
        Page 3
    Frontispiece
        Page 4
    Main
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
Full Text



Bulletin 258 April, 1933


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA
Wilmon Newell, Director










THE PECAN SHUCKWORM
By FRED W. WALKER





















Bulletins will be sent free upon application to the
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA













EXECUTIVE STAFF BOARD OF CONTROL

John J. Tigert, M.A., LL.D., President of the Raymer F. Maguire, Chairman, Orlando
University A. H. Blanding. Bartow
Wilmon Newell, D.Sc., Director A. H. Wagg, West Palm Beach
H. Harold Hume. M.S., Asst. Dir., Research Geo. H. Baldwin, Jacksonville
Harold Mowry, B.S.A., Asst. Dir., Adm. J. T. Diamond, Secretary, Tallahassee
J. Francis Cooper, M.S.A., Editor
R. M. Fulghum, B.S.A., Assistant Editor
Ida Keeling Cresap, Librarian BRANCH STATIONS
Ruby Newhall, Administrative Manager B AN A IN
K. H. Graham, Business Manager
Rachel McQuarrie, Accountant NORTH FLORIDA STATION, QUINCY
L. O. Gratz, Ph.D., Plant Pathologist in Charge
R. R. Kincaid, M.S., Asst. Plant Pathologist
AIN STATION GAI IW. A. ACarver, Ph.D., Associate Agronomist
MAIN STATION, GAINESVILLE R. M. Crown, B.S.A., Assistant Agronomist
Jesse Reeves, Farm Superintendent
AGRONOMY
W. E. Stokes, M.S., Agronomist** CITRUS STATION, LAKE ALFRED
"W. A. Leukel, Ph.D., Agronomist. Jer, Su
G. E. Ritchey, M.S.A., Associate* John H. Jefferies, Superintendent
Fred H. Hull, M.S., Associate Geo. D. Ruehle, Ph.D., Associate Plant Pathol-
J. D. Warner, M.S., Associate ogist
John P. Camp, M.S., Assistant W. A. Kuntz, A.M., Associate Plant Pathologist
B. R. Fudge, Ph.D., Associate Chemist
ANIMAL HUSBANDRY W. L. Thompson, B.S., Assistant Entomologist
A. L. Shealy, D.V.M., Animal Husbandman*
R. B. Becker, Ph.D., Specialist in Dairy Hus- EVERGLADES STATION, BELLE GLADE
Sbandry R. V. Allison, Ph.D., Soils Specialist in Charge
W. M. Neal, Ph.D., Associate in Animal Nutri- R. N. Lobdell, M.S., Entomologist
tion F. D. Stevens, B.S., Sugarcane Agronomist
E. F. Thomas, D.V.M., Assistant Veterinarian G. R. Townsend, Ph.D., Asst. Plant Pathologist
W. W. Henley, B.S.A., Assistant Animal Hus- B. A. Bourne, M.S., Sugarcane Physiologist
bandman J. R. Neller, Ph.D., Biochemist
P. T. Dix Arnold. B.S.A., Assistant in Dairy In- A. Daane, Ph.D.. Agronomist
vestigations R. W. Kidder, B.S., Asst. Animal Husbandman
CHEMISTRY AND SOILS Ross E. Robertson, B.S., Assistant Chemist
R. W. Ruprecht, Ph.D., Chemist"* SUB-TROPICAL STATION, HOMESTEAD
R. M. Barnette, Ph.D., Chemist
C. E. Bell, Ph.D., Associate H. S. Wolfe, Ph.D., Horticulturist in Charge
J. M. Coleman, M.S., Assistant W. M. Fifield, M.S., Assistant Horticulturist
H. W. Winsor, B.S.A., Assistant Stacy O. Hawkins, M.A., Assistant Plant
H. W. Jones, M.S., Assistant Pathologist

ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agricultural Economist**
Bruce McKinley, A.B., B.S.A., Associate
M. A. Brooker, Ph.D., Associate FIELD STATIONS
Zach Savage, M.S.A., Assistant
Leesburg
ECONOMICS, HOME M. N. Walker, Ph.D., Plant Pathologist in
Ouida Davis Abbott, Ph.D., Specialist** Charge
L. W. Gaddum, Ph.D., Biochemist W. B. Shippy, Ph.D., Associate Plant Pathol-
C. F. Ahmann, Ph.D., Physiologist ogist
K. W. Loucks, M.S., Asst. Plant Pathologist
ENTOMOLOGY J. W. Wilson, Ph.D., Associate Entomologist
J. R. Watson, A.M., Entomologist** C. C. Goff, M.S., Assistant Entomologist
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A. Assistant Plant City
P. W. Calhoun, Assistant, Cotton Insects A. N. Brooks, Ph.D., Plant Pathologist
R. E. Nolen, M.S.A., Asst. Plant Pathologist
HORTICULTURE Cocoa
A. F. Camp, Ph.D., Horticulturist**
M. R. Ensign, M.S., Associate A. S. Rhoads, Ph.D., Plant Pathologist
A. L. Stahl, Ph.D., Associate
G. H. Blackmon, M.S.A., Pecan Culturist Hastings
C. B. Van Cleef, M.S.A., Greenhouse Foreman A. H. Eddins, Ph.D., Asso. Plant Pathologist

PLANT PATHOLOGY West Palm Beach
W. B. Tisdale, Ph.D., Plant Pathologist** D. A. Sanders, D.V.M., Veterinarian
George F. Weber, Ph.D., Plant Pathologist Monticello
R. K. Voorhees, M.S., Assistant
Erdman West, M.S., Mycologist Fred W. Walker, Assistant Entomologist

*In cooperation with U.S.D.A. Bradenton
"**Head of Department. David G. Kelbert, Asst. Plant Pathologist


















CONTENTS






PAGE

INTRODUCTION ........................................ .... 5

HISTORY AND SYNONYMY................. ......................... 5

DISTRIBUTION ............................................. 5

FOOD PLANTS ............................................. 6

LIFE HISTORY AND DESCRIPTION ........... ....... ................. 6

SEASONAL HISTORY .................... .......................... 9

CHARACTER OF INJURY .............. ........................ 9

NATURAL ENEMIES ................ ............................... 11

EXPERIMENTAL WORK .................. ......................... 12
Extent of injury ............ .......................... 12
Control experiments .................................... ... 14

CONTROL ............ ............................................ 15

SUMMARY .............. . ................ ........... .... 16

LITERATURE CITED .............. ................................. 18

































f..

Fig. 1.Ol husk reann ontetre uh sson ntibcyr
pecantreecarr the hcwrmtruhth itr











THE PECAN SHUCKWORM
Laspeyresia caryana (Fitch)
By FRED W. WALKER

INTRODUCTION
The pecan or hickory shuckworm, Laspeyresia caryana (Fitch),
formerly was considered to be an insect of minor importance by
many pecan growers. Investigations covering a period of nearly
five years have proved this to be an erroneous conclusion. Most
growers have been paying a heavy annual tribute to this insect
without realizing it. During 1927 at least 25% of the pecan crop
in Florida was destroyed by the shuckworm.
The shuckworm is closely related to some of our most important
insect pests, namely, the oriental peach moth, Grapholitha molesta
(Busck), and the notorious codling moth, Carpocapsa pomonella
(Linn.).
HISTORY AND SYNONYMY
The pecan or hickory shuckworm was first described by
Fitch(2) from Easton, New York, in 1856 under the name
Ephippiphora caryana. In 1869, Shimer(7) gave it the name
Grapholitha caryae. In 1903 it was listed in Dyar's Check List
of North American Lepidoptera(1) under number 5268, as
Enarmonia caryana Fernald. In 1923, Forbes(3) listed it under
the name Laspeyresia caryana Fitch. In 1926, Heinrich(5), in
his revision of this group, listed it under the name Laspeyresia
caryana (Fitch).
The genus to which the shuckworm belongs is represented in
North America by 36 species according to this revision. Since
the publication of this revision, another species, Laspeyresia
plametum Heinrich, has been described in the Proceedings of the
Entomological Society of Washington(6).

DISTRIBUTION
The shuckworm is probably a native of the eastern part of the
United States. No records are available to show how long the
insect has been present in Florida but Gossard(4) recorded it as
early as 1905. In all probability it was present in Florida long
before the first pecan tree was planted here. It has been found








6 Florida Agricultural Experiment Station


in practically every pecan grove that has been inspected in the
state (Table I).
The shuckworm has been recorded from New York, New Jer-
sey, Pennsylvania, District of Columbia, Maryland, Virginia,
Texas, Missouri, Mississippi, Louisiana, Arkansas, South Caro-
lina, North Carolina, Alabama, Georgia and Florida. It is prob-
ably present all over the eastern portion of the United States,
wherever its food plants occur.
FOOD PLANTS
The food of the shuckworm larva consists chiefly of the husks
of various hickories, in which group of trees the pecan is included.
It has been found occasionally in the husks of the black walnut
also. In the early spring, before the nuts are large enough to
become infested, it is sometimes found feeding in the galls of
Phylloxera on hickory and pecan.
The other species in the genus Laspeyresia have a wide range
of food plants. Most of them feed in the cones of pine, fir, larch,
spruce and cypress. One species feeds in the bark of poplar.
Another species, Laspeyresia nigricana (Stephens), which was
introduced from Europe, feeds on the garden pea and is of
economic importance. Most of the insects belonging to this genus
feed on seeds or seed coverings.
LIFE HISTORY AND DESCRIPTION
The adult of the shuckworm is a small moth with a wing spread
of 10-12 mm. (a little less than half an inch). The fore wings
are deep brownish black, tinged with iridescent purplish. There
are from five to seven pale, yellowish streaks showing on the
front margins of the fore wings. The hind wings are fuscous,
whitish on basal half, fringe whitish, tinged with fuscous; veins
3 and 4 united at base.
The moths do not take wing readily when disturbed and, be-
cause of this habit and their protective coloration, they are rarely
seen in the pecan grove, even by close observers.
The egg is small and when first laid is pearly white; this color
gradually changes to reddish as incubation advances. Under
magnification the shell of the egg appears to be reticulated.'
Sometimes a chalky white deposit surrounds the.place where the
egg of the shuckworm has hatched. In some cases, however,
the egg may be deposited on the calyx and the nut show no ex-








Bulletin 258, The Pecan Shuckworm 7

TABLE I.-PERCENT OF SHUCKWORM INFESTATION OCCURRING IN DIFFERENT
LOCALITIES OF THE STATE IN AUGUST, 1927.
Number
Locality Variety of Nuts Percent
Examined Infested
Orlando ................Schley ............. 78 00
Hague .................. Schley .............. 18 55.6
Newberry .............. Randall ............ 64 50.0
.............. ? ... ...... 320* 10.9
Orange Heights .........VanDeman ......... 247 63.6
"......... Teche .............. 321 63.3
......... Curtis .............. 160 76.3
Jacksonville ............Simmons ........... 49 28.6
...........Stuart ............. 73 39.7
...........M oore .............. 93 37.6
Mandarin .............. Schley ............ 936 33.3
..............Delm as ............. 201 59.2
Baldwin ............... Curtis .............. 290 51.7
...............Stuart ............. 150 52.7
Lake City ..............Mixed .............. 194 38.4
W ellborn ............... Mixed .............. 103 49.5
Havana ................. Moore .............. 35 34.3
................ W aukeenah ......... 44 52.3
................ Schley ............. 181 63.0
................ Seedling ............ 138 60.1
................ Clark .............. 78 60.2
................Bolton ............. 192 70.8
................Stuart .............. 51 56.9
Concord ................ Sweet Meat ........ 9 77.8
.............. Columbia ........... 33 45.4
Paxton ................ Seedling ........... 78 42.3
................ VanDeman ......... 47 59.6
................ Randall ............ 38 55.2
...............Schley ............. 76 56.6
................ Stuart ............. 174 41.9
................ Pabst .............. 118 50.0
................Teche .............. 151 54.0
................ Frotscher ........... 71 39.4
................ Success ............. 97 64.9
...............Elliott .. .......... 47 48.9
Chipley ........ ..... .Mobile ............. 19 68.4
................ M oore .............. 87 48.3
...............Success ............. 63 55.6
................Teche .............. 20 55.0
................ Moneymaker ........ 26 61.6
................ Frotscher ........... 30 83.3
................ Stuart ............. 12 25.0
................ Schley .............. 157 58.6
................N elson ............. 15 66.7
Bonifay ................ Success ............ 173** 72.3
................Moneymaker ........ 47 55.3
Greensboro ............. Seedling ............ 19 73.7
............ Kennedy ... . ... 16 81.3
.... ....... President ........... 17 47.0
..............Schley ............. 100 47.0
..............Stuart .............. 78 34.6
..............VanDeman. ....... 52 55.7
Chattahoochee .......... Hicoria aquatica ..... 300 95.0
River Junction .......... Hicoria sp. ......... 163 97.4
.......... Hicoria alba ........ 60 50.0
Liberty County ......... Hicoria sp........... 145 71
*Nuts so badly infected by scab that they had almost dried up. If infested by shuck-
worm the larvae died before they could penetrate very far.
**Nuts from a single tree, estimated to have dropped 65% of the crop set.







8 Florida Agricultural Experiment Station

ternal signs of infestation, until it is cut into and the workings
of the larvae are disclosed. The incubation period during the
summer is usually from five to seven days, but during the fall
when the temperature is lower, this period is slightly longer.
The larva when first hatched is a small, whitish caterpillar,
with three pairs of true legs and five pairs of abdominal feet or
false legs. Immediately upon hatching the larva enters the nut
and usually does not leave it until it emerges as an adult moth.
When mature and ready
to pupate, the larva (Fig.
2) is about 8-10 mm. (a
third to two-fifths of an
inch) in length, with a
creamy or dirty white
body and a brownish
head. Before pupating,
the larva tunnels to the
outer covering of the
husk and cuts a semicir-
cular opening through
which the adult can
emerge. The pupal cham-
ber is lined with, silk.
During the summer
months the larval period
is from 19 to 32 days;
during the winter from
110 to 150 days.
"The pupa of the shuck-
worm is very variable in
size, measuring from 5-8
Fig. 2.-Nearly mature larva of shuckworm mm. (a fifth to a third of
in husk. (About twice natural size.) an inch) in length, with
an average of about 6 mm. (one-fourth inch). Immediately after
transformation from the larva, the pupa is light yellowish brown.
This soon changes to a darker brown and as the time for emer-
gence approaches the pupa becomes blackish. The pupae are
generally found in the husks, but where the husks are buried
before the larvae pupate, they sometimes tunnel to the surface of
the soil and pupate there. The larvae which pupate at the sur-
face of the ground construct the pupa cases of silk and sand.







Bulletin 258, The Pecan Shuckworm 9

During the summer months the pupal period is from four to 11
days. During the early spring it is much longer, generally from
14 to 28 days, but sometimes extending over a period of several
months.
SEASONAL HISTORY
In the extreme northern portion of its range there is probably
only one brood of the shuckworm each year. In the northern
portion of the pecan-growing area, however, there are at least
two broods each year, while in the southern portion of the pecan-
growing area there are at least four and sometimes five. This
increase in the number of broods on account of the longer growing
season causes a greater percentage of loss to the pecan growers
of the southern portion of the area. During the summer the
broods of the shuckworm overlap, so that it is almost impossible
to distinguish between broods. Adults of the shuckworm have
been found in the field from February 18 to October 5, and larvae
can be found any month in the year. In the northern portion of
Florida, the majority of the overwintering larvae emerge as
adults during the latter part of March and the first part of April.
Most of the first adults to emerge probably deposit their eggs
on the galls of Phylloxera on hickory or pecan. Some of the
adults emerging later deposit eggs on young hickory nuts. Eggs
of adults emerging from this first brood can be found on pecans as
early as June 15.
CHARACTER OF INJURY
The injury done by the shuckworm is of four distinct types.
First: The total destruction of the nut. This type of injury
is done by the earlier broods. Whenever the egg of a shuckworm
moth, hatches on a young nut and the larva enters, the nut falls
to the ground and is a total loss to the grower. Some of these
early drops have been attributed to scab and physiological con-
ditions, due to the fact that the entrance hole of the shuckworm
is so small that it is hardly noticeable. In some cases there may
be no external sign that the nut is infested, as the larva sometimes
enters through the blossom end. Sometimes, but not always,
there may be a whitish, chalky spot around where the egg hatched.
A careful paring away of this spot will usually disclose a tiny,
brown spot where the larva entered. The tunnels made by the
shuckworm larvae are usually plugged with frass. Some of the
larvae show the same habit as most of the other internal feeding







10 Florida Agricultural Experiment Station

lepidopterous larvae, which is to discard the first few mouthfuls
from the outer portion of the host plant. This habit has been
observed in a few of the newly hatched larvae. Nuts infested
by the shuckworm larva before the shell has hardened will usually
fall before maturity.
Second: Causing failure of kernels to fill properly. Nuts which
become infested by the larvae of the shuckworm late in summer
or after the shell has hardened may remain on the trees until
maturity but a large proportion of these will have the kernel so
poorly filled that they are almost worthless. This failure of the
kernel to fill properly is due to the cutting off of the food supply
which enters the nut through its base. One of the favorite places
for the larvae of
the shuckworm to
feed is the thick-
ened area in the
husk at the base
of the nut. Since
the food passages
enter the nut
through this por-
tion, some of them
are likely to be
destroyed and
consequently the
amount of nour-
ishment reaching
the kernel is re-
Fig. 3.-Sooty markings on pecan shells caused by d t
the shuckworm. duced to some ex-
tent.
Third: By scarring nuts and causing the husk to stick. Nuts
which have been heavily infested by the shuckworm often show
markings on the shell from the tunnels of the larvae. Most of
these nuts will have part of the husk stick to the shell so as to
leave a sooty mark when it is removed (Fig. 3). Nuts which
show a high percentage with these sooty marks will not sell for
good prices. Even the "crackeries" do not care to buy nuts that
have a large percentage marred by these sooty marks because
experience has taught them that these nuts are usually poorly
filled and consequently cost them more per pound for perfect
kernels than those that do not show such markings.
Fourth: Delayed maturity. Nuts heavily infested by the







Bulletin 258, The Pecan Shuckworm 11

shuckworm are usually much later in maturing than non-infested
or slightly infested nuts. If at harvest time part of the nuts on
the trees have ripened and the husks opened but a large portion
of them are still green and unopened, it is usually a sign of a
heavy shuckworm infestation. These green, unopened nuts will
usually be from 95 to 100 percent infested. The larger portion
of these heavily infested nuts will be so poorly filled that they
are not worth harvesting.

NATURAL ENEMIES
There are a number of parasitic and predatory insects which
attack the larvae of the shuckworm. These are rarely abundant
enough, however, to reduce the infestation to any great extent.
Usually less than 30 percent of shuckworm larvae will be de-
stroyed by these agencies each year. In the northern portion of
Florida the family Tachinidae is probably the most important
group of the parasitic insects, as over 50 percent of the parasitised
larvae are killed by this group. The family Ichneumonidae ranks
second in the destruction of larvae. This last family, while more
abundant in numbers of species, is not so numerous in individuals.
The egg parasite Trichogramma minutum Riley, has been bred
sparingly from the eggs of the shuckworm. Among the preda-
tors, only two species have been definitely connected with the
destruction of shuckworm larvae. These are the harvest mite
Pediculoides ventricosus Newport and the larvae of the ground
beetle Harpalus sp. These predators have been found only in
husks on the ground during the winter months. Most of the
parasites also have been found in overwintering larvae but some
have been found in larvae of the summer broods.
Some overwintering larvae have been found that were infected
with entomogenous fungi belonging to the genus Isaria. Since
the percentage of larvae infected by this fungus is very small, it
is apparently not an important factor in the reduction of the
shuckworm infestations. Except under favorable weather con-
ditions, fungous diseases are rarely of much importance in the
reduction of insect infestations. Rain is probably one of the
greatest factors in reducing shuckworm infestations in localities
where no artificial methods of control are used. Heavy rains dur-
ing the summer months wash many of the eggs from the nuts
before they hatch.








12 Florida Agricultural Experiment Station

EXPERIMENTAL WORK

EXTENT OF INJURY
Records were kept of the drops from 10 trees of one variety to
determine as nearly as possible the amount of damage done by
the shuckworm. During the period in which the nuts were
dropping, a total of 9,567 were picked up, of which 5,177, or 54.11
percent, were infested by shuckworm. The non-infested nuts
from these trees averaged 64 to the pound when mature. Using

TABLE II.-PERCENTAGE OF INFESTATION BY LOCALITIES.
Locality Percent Infestation
Bonifay ........................................ 67.4
Baldwin ...................................... 52.0
Chipley .......................... ............ 57.5
Concord ................. ..................... 52.4
Greensboro ..................................... 48.9
Hague ......................................... 55.5
Jacksonville ............... ................... 36.3
Lake City .................. ..................... 38.4
M andarin ....................................... 37.9
Newberry ....................................... 17.5
Orange Heights ................................. 66.2
Orlando ........................................ 00.0
Paxton ........................................ 53.5
W ellborn ....................................... 45.5

TABLE III.-PERCENTAGE OF INFESTATION BY VARIETIES.
Variety Percent Infested
Bolton ......................................... 70.8
Clark ........................................... 60.2
Columbia .................................... .. 45.4
Curtis ......................................... 60.4
Delm as ........................................ 59.2
Elliott .................. ........................ 48.9
Frotscher ............................. .. ....... 54.0
Kennedy ....................................... 81.2
Mobile ......................................... 68.4
Moore ............. ..... ........................ 41.4
Moneymaker .................................... 56.7
Nelson ................. ...................... 66.7
Pabst ........................................... 50.0
President ...................................... 47.0
Randall ........................................ 52.0
Schley ........................................ 44.7
Simmons .................. ...................... 28.6
Stuart ......................................... 44.6
Success ........................................ 67.7
Sweet Meat .................. .................. 77.8
Teche ......................................... 60.4
VanDem an ................................ ..... 61.8
Waukeenah ..................................... 55.8
Seedlings ...................................... 31.8
Hicoria aquatic ................................ 95.0
H icoria spp. ................................... 72.9
The above figures are based on a total of 6,500 pecan and 668 hickory nuts, gathered from
various localities in Florida.






TABLE IV.-EFFECT OF SHUCKWORM INFESTATION UPON CONDITION OF MATURED NUTS.
Lot No. of Nuts Percentage Percentage Percentage Percentage Percentage
No. Variety Condition Per Pound Husk Sticking Scarred Well Filled Poorly Filled Pops
3A Moneymaker.... Non-infested ......... 83 00.0 00.0 51.0 48.9 00.0
7A Moneymaker .... Non-infested ......... 72 00.0 00.0 58.3 40.7 00.9
1 Moneymaker.... Infested ............. 72.6 31.0 14.0 28.0 68.0 4.0
3 Moneymaker ... .Infested ............. 94 34.0 13.2 22.6 56.6 20.9
7 Moneymaker.... Infested ............. 77 27.7 22.3 16.9 72.3 10.8
13 Moneymaker .... Composite ........... 64 18.5 8.7 67.4 30.4 2.2
14 Moneymaker. .... Composite ........... 64 16.7 5.9 40.0 57.1 2.4
15 Moneymaker .... Composite ........... 70 22.8 8.6 51.4 47.1 1.4
16 Moneymaker.... Composite ........... 68.6 15.1 6.8 15.1 83.6 1.4 z'
17 Moneymaker.... Composite ........... 65 15.1 4.7 53.8 43.4 2.8
18 Moneymaker .... Composite ........... 60 21.4 7.1 76 8 17.8 5.3
19 Moneymaker.... Composite ........... 57 415 16.9 57.1 35.2 7.6
23A Schley...........Non-infested (green).. 64 00.0 00.0 25.0 75.0 0.0
20 Schley.......... Composite ........... 61 9.3 4.7 72.9 25.2 1.9 >
2 Schley.......... Infested ............. 70.5 12.8 3.5 44.7 46.8 8.5
21 Schley.......... Infested ........... 97 39.2 8.2 8.2 36.7 55.1 10
22 Schley.......... Infested (green)...... 99 403 13.9 6.5 31.1 62.4
23 Schley.......... Infested (green) ...... 96 32.2 7.9 3.3 37.5 59.2
24 Schley...... ... .Infested (green)...... 107 36.1 11.7 4.8 35.6 59.9
27 Schley..........Infested ............. 80 21.2 00.0 36.8 40.0 23.0 t
4A Moore ......... Non-infested ......... 80 00.0 00.0 63.2 36.8 00.0
4 Moore..........Infested ............. 80 31.2 16.8 44.0 56.0 00.0
6 Moore.......... Infested ............. 86.7 50.5 16.3 46.3 51.0 2.6
8 Moore.......... Composite ........... 144 37.8 35.2 00.0 25.9 74.1
9 Moore.......... Composite ........... 79 51.5 33.1 46.6 50.3 3.1
10 Stuart.......... Non-infested ......... 59.5 00.0 00.0 92.6 7.4 00.0
12A Stuart.......... Non-infested ......... 50 00 0 00.0 64.0 36.0 00.0
12 Stuart.......... Infested ............. 60.8 45.6 30.6 47.6 50.3 2.0
5 Stuart.......... Infested ............. 57 61.4 51.7 57.0 41.2 1.8
11A Frotscher ...... Non-infested ......... 45.7 00.0 00.0 90.0 10 0 00.0
11 Frotscher ..... Infested ............. 52.8 15.1 9.9 81.8 18.2 00.0
26A Curtis..........Non-infested ......... 80 00.0 00.0 85.0 15.0 00.0
26 Curtis.......... Infested ............. 94 72.0 42.8 44.5 39.6 15.9
NOTE-Lots 3, 3A, 4, 4A, 7, 7A, 11, 11A, 12, 12A, 26 and 26A are infested and non-infested nuts collected from the same trees of each variety. wC







14 Florida Agricultural Experiment Station

this figure as a standard for comparison, the total weight of the
drops from these 10 trees would have been 149.1 pounds of nuts,
of which 80.6 pounds were shed because of shuckworm infestation.
This does not take into consideration the loss due to light weight
of the infested nuts which remained on the trees until harvest.
At the time of harvest, 53 percent of the nuts on these trees were
shuckworm-infested. These infested nuts averaged 77 to the
pound. This shows a loss of over 20 percent in weight on over
half the nuts produced.
CONTROL EXPERIMENTS
A series of preliminary burying experiments was conducted to
determine whether the shuckworm could be controlled by plowing
under the husks. In these experiments, husks with a known
number of larvae or pupae were buried under cages in two types
of pecan soil. The depths at which these husks were buried were
from one to four inches. As a check the same number of larvae
or pupae in husks were kept on the surface in cages. Daily records
TABLE V.-EFFECT OF BURYING INFESTED PECAN HUSKS UPON THE CONTROL
OF THE SHUCKWORM, 1927-32.
Cage Stage of Depth Soil Percentages of Emergence
No. Insect Buried Type 1927 1928 1929 1930 1931 1932
"1 Larvae Surface 50 44 63 82 76 72
2 Larvae 1 inch Light 12 41 48 52 61 68
3 Larvae 2 inches Light 8 37 44 40 47 51
4 Larvae 3 inches Light 6 40 39 28 31 29
5 Larvae 4 inches Light 4 36 26 22 19 35
6 Larvae 1 inch Heavy 0 15 30 20 26 34
7 Larvae 2 inches Heavy 0 11 20 22 29 27
8 Larvae 3 inches Heavy 0 6 18 12 16 17
9 Larvae 4 inches Heavy 0 11 8 10 9 19
10 Pupae Surface 52 100 84 96 89 83
11 Pupae 1 inch Light 6 0 2 4 10 12
12 Pupae 2 inches Light 0 2 0 0 0 2
13 Pupae 3 inches Light 2 2 0 0 0 0
14 Pupae 4 inches Light 0 2 0 0 0 0
15 Pupae 1 inch Heavy 14 25 2 4 0 2
16 Pupae 2 inches Heavy 0 6 0 8 0 0
17 Pupae 3 inches Heavy 0 4 0 0 0 0
18 Pupae 4 inches Heavy 0 0 0 0 0 0

of the emergence in these cages was kept and the percentage of
adults emerging was computed. The results of these experiments
(Table V), show that the shuckworm can be controlled or reduced
by the plowing under of the husks.
Another experiment, to check on the burying experiments, was
conducted in a 20-acre orchard. In this experiment the husks








Bulletin 258, The Pecan Shuckworm 15

were knocked from the trees and plowed under during March. In
1930 when this experiment was begun, there was only a medium
infestation in this orchard. At harvest time there was an aver-
age of 22 percent. The average infestation in some of the larger
groves in the vicinity of this experiment was 58.6 percent. This
shows a reduction in percentage of infestation due to plowing,
even though the orchard in this experiment is close to two other
orchards in which no control measures were employed.
CONTROL
Experiments have shown that the number of shuckworm adults
emerging in the spring can be reduced by plowing under the old
husks. These experiments have shown also that the percentage
of reduction will be greater if the plowing is delayed until the
larger portion of the larvae have pupated (Table V, cages 11-18).
Where the husks are turned under with the insects in the larval
stage, some of them leave the husks and tunnel to the surface,
where they pupate. Larvae that pupate on or near the surface
can emerge easily. Since most of these larvae pupate during
February, the results should be much better if the plowing is
delayed until about the first week of March than if done earlier.
On account of the variation of the pupation period from year to
year it is best to examine a number of the old husks and determine
what stage the insect is in before plowing under the husks. Before
any plowing is commenced, however, all old husks should be
knocked from the trees and raked back from the trunks for a
few feet so that the plow can cover them without injury to the
trees.
By far the best method for the control of this insect is the
destruction of all old husks by burning. This method is feasible,
however, only where the nuts have been harvested on sheets so
that all refuse can be piled for burning without too much expense.
Where this method of harvesting is used, the piles of refuse should
be placed in every second middle, having the husks and leaves
from four trees in each pile; this will prevent having too many
fires to watch, when the husks are being burned. These piles
should be far enough from the trees so that the heat will do no
injury. Where there is dry grass in the grove, care should be
taken that the fires do not get away and injure the trees.
In any method of control used, it must be remembered that the
adult is a winged insect and is capable of flying considerable dis-







16 Florida Agricultural Experiment Station

tances, so that the larger the area over which control measures
are carried on, the better the results will be. However, every
larva destroyed will leave just that many less to begin with in
the spring. The cost of controlling or reducing the damages done
by this insect is very small, compared with the value of the nuts
that can be saved. Where orchards are located near towns in
which there are many pecan trees in back yards, or near wood-
lands containing
hickories that
cannot be cleared
up, the control
will not be as good
: F j as in isolated
.. plantings. The
Menace of back-
yard trees lies in
the fact that in
most cases the
nuts remain on
the trees until
they drop, instead
i' of being threshed
S off as in commer-
S. cial plantings.
"Failure to thresh
leaves the old
Fig. 4.-Normal nuts, free of blemishes caused by husks remaining
the shuckworm. husks remaining
on the trees (Fig.
1). Where possible, all bearing hickory trees near commercial
plantings should be cut down.
The shuckworm can not be controlled by the use of sprays
because it feeds on the inside of the husk or nut, where no spray
can reach it and in most cases the larva discards the outside portion
of the husk before entering. Since, because of the overlapping
of broods, the egg-laying period is very long, the use of ovicides to
destroy the eggs is impracticable.

SUMMARY

The shuckworm is a pecan pest of major importance. It has
been found in practically every pecan orchard in Florida and in







Bulletin 258, The Pecan Shuckworm 17

nearly every pecan producing state in the eastern portion of the
United States.
The food of the shuckworm consists of the husks of the pecan
and various other species of hickory. The shuckworm has also
been found feeding in the husks of the black walnut. In the early
spring it is sometimes found feeding in the galls of Phylloxera on
hickory and pecan.
The incubation period of the egg is usually from five to seven
days. The larval period during the summer is from 19 to 32 days,
and in winter from 110 to 150 days. In Florida there are four
broods each year and sometimes five. Adults have been found
in the field from February 18 to October 5. The larvae can be
found every month in the year.
The injury done by the larvae consists of total destruction of
young nuts by earlier broods, poor filling of infested nuts, marring
of nuts with sooty marks or scars from tunnels of larvae, and
delayed maturity.
There are a number of natural enemies of the shuckworm, both
predaceous and parasitic, including fungous diseases, but none
of these agencies are numerous enough to reduce the shuckworm
to such an extent that artificial control is unnecessary. Heavy
rains during the summer months destroy some of them by wash-
ing the unhatched eggs from the nuts.
The amount of damage done by the shuckworm can be mate-
rially reduced by plowing under the husks during the early part
of March. Before doing this all old husks should be knocked from
the trees and raked back from the trunks. The larger the area
over which control measures are carried on, the better the results
will be. By far the best method of controlling the shuckworm
is the total destruction of all old husks by burning. This method
is feasible only where the nuts have been harvested on sheets so
that the refuse can be placed in piles. The cost of control mea-
sures for the shuckworm is very little compared with the value of
the nuts that can be saved. All bearing hickories in the vicinity
of orchards should be cut down if possible as they are a source
of reinfestation.








18 Florida Agricultural Experiment Station

LITERATURE CITED

1. DYAR, H. G. List of North American Lepidoptera. Bul. 52 U. S. Nat.
Mus. (No. 5268). 1903.
2. FITCH, ASA. Third .Report on the Noxious and Other Insects of New
York. P. 459. 1856.
3. FORBES, W. T. C. Lepidoptera of New York and Neighboring States.
Cornell Agr. Exp. Sta. Mem. 68, p. 392. 1923.
4. GOSSARD, H. A. Insects of Pecan. Fla. Exp. Sta. Bul. 79, p. 305. 1905.
5. HEINRICH, CARL. Revision of North American Moths of Subfamilies
Laspeyresiinae and Olethreutinae. U. S. N. M. Bul. 132, p. 55. 1926.
6. Proc. Ent. Soc. Washington. 30:6. 1928.
7. SHIMER, HENRY. Trans. Am. Ent. Soc. Vol. 2, p. 394. 1869.





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