Bulletin 466 January, 1950
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
HAROLD MOWRY, Director
Control of Budworms, Earworms
and Other Insects Attacking
Sweet Corn 0 Green Corn
By E. G. KELSHEIMER, N. C. HAYSLIP and J. W. WILSON
Entomologists, Florida Agricultural Experiment Stations
Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
BOARD OF CONTROL EDITORIAL
Frank M. Harris, Chairman, St. Petersburg J. Francis Cooper, M.S.A., Editor'
N. B. Jordan, Quincy Clyde Beale, A.B.J., Associate Editors
Hollis Rinehart, Miami
Eli H. Fink, Jacksonville
George J. White, Sr., Mount Dora ENTOMOLOGY
W. F. Powers, Secretary, Tallahassee
A. N. Tissot, Ph.D., Entomologist'
L. C. Kuitert, Ph.D., Assistant
EXECUTIVE STAFF H. E. Bratley, M.S.A., Assistant
J. Hillis Miller, Ph.D., President of the
Harold Mowry, M.S.A., Director HOME ECONOMICS
L. 0. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield, M. S., Asst. Dir. Admin. Ouida D. Abbott, Ph.D., Home Econ.'
Geo. F. Baughman, M.S., Business Manager' R. B. French, Ph.D., Biochemist
Claranelle Alderman, Accountants
MAIN STATION, GAINESVILLE G. H. Blackmon, M.S.A., Horticulturist'
F. S. Jamison, Ph.D., Horticulturist"
AGRICULTURAL ECONOMICS Albert P. Lorz, Ph.D., Horticulturist
C. V. Noble, Ph.D., Agri. Economist H. M. Reed, B. S., Chem., Veg. Processing
. E. L. Greene, Ph.D., Agri. Economist R. K. Showalter, M.S., Asso. Hort.
Zach Savage, M.S.A., Associate R.A. Dennison, Ph.D., Asso. Hort.
A. H. Spurlok, M.S.A., Associate R. H. Sharpe, M. S., Asso. Hort.
D. E. Alleger, M.S., Associate R. Wilmot, M.S.A., Asst. Hort.
D. L. Brooke, M.S.A., Associate R. D. Dickey M.S.A., Asst. Hort.
M. R. Godwin, Ph.D., Associate Victor F. Nettles, Ph.D., Asst. Hort.
H. W. Little, M.., Assistant L. H. Halsey, M.S.A., Asst. Hort.
TallmH. W.adge Bergen, B.S., Assistant F. S. Lagasse, Ph.D., Asso. Hort.2
Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist LIBRARY
J. C. Townsend, Jr., B.S.A., Agr.
Statistician' Ida Keeling Cresap, Librarian
J. B. Owens, B.S.A., Agr. Statistician
J. F. Steffens, Jr., B.S.A., Agr. Statistician
AGRICULTURAL ENGINEERING W. B. Tisdale, Ph.D., Plant Pathologist' "
Frazier Rogers, M.S.A., Agr. Engineer' 8 Phares Decker, Ph.D., Plant Pathologist
J. M. Johnson, B.S.A.E., Asso. Agr. Erdman West, M.S., Mycologist and Botanist
Engineer Howard N. Miller, Ph.D., Asso. Plant Path.
J. M. Myers, B.S., Asso. Agr. Engineer Lillian E. Arnold, M.S., Asst. Botanist
R. E. Choate, B.S.A.E., Assistant. Agr. Robert W. Earhart, Ph.D., Plant Path.2
A. M. Pettis, B.S.A.E., Asst. Agr. Engineer' a POULTRY HUSBANDRY
AGRONOMY N. R. Mehrhof, M.Agr., Poultry Hush.1 '
J. C. Driggers, Ph.D., Asst. Poultry Husb.3
Fred. H. Hull, Ph.D., Agronomist'
G. E. Ritchey, M.S., Agronomist2 SOILS
G. B. Killinger, Ph.D., Agronomist'
H. C. Harris, Ph.D., Agronomist3 F. B. Smith, Ph.D., Microbiologisti'
R. W. Bledsoe, Ph.D., Agronomist Gaylord M. Volk, Ph.D., Chemist
W. A. Carver, Ph.D., Associate J. R. Henderson, M.S.A., Soil Technologist'
Darrel D. Morey, Ph.D., Associate J. R. Neller, Ph.D., Soils Chemist
Fred A. Clark, B.S., Assistant Nathan Gammon, Jr., Ph.D., Soils Chemist
Myron C. Grinnell, B.S.A.E., Assistant R. A. Carrigan, Ph.D., Biochemist3
M. N. Gist, Collaborator2 Ralph G. Leighty, B.S., Asso. Soil Surveyor
Geo. D. Thornton, Ph.D., Asso.
ANIMAL HUSBANDRY AND NUTRITION H.W. Winsor, B.S.A., Assistant Chemist
SS Glasscock Ph.D., An. Hus R. E. Caldwell, M.S.A., Asst. Chemist'
R. S. Glasscock, Ph.D., An. Husbandman V. W. Cyzycki, B.S., Asst. Soil Surveyor
J. E. Pace, B.S.A., Asst. An. Husbandman R. B. Forbes, M.S., Asst. Soils Chemist
S. John Folks, B.S.A., Asst. An. W. L. Pritchett, M.S., Asst. Chemist4
Husbandman James H. Walker, M.S.A., Asst. Soil
T. J. Cunha, Ph.D., Assoc. An. Husbandman Surveyor
G. K. Davis, Ph.D., Animal Nutritionist Walter J. Friedmann, M.S.A., Asst.
R. L. Shirley, Ph.D., Biochemist Biochemist
Katherine Boney, B.S., Asst. Chem. O. E. Cruz, B.S.A., Asst. Soil Surveyor
DAIRY HUSBANDRY AND DAIRY VETERINARY SCIENCE
D. A. Sanders, D.V.M., Veterinarian'
E. L. Fouts, Ph.D., Dairy Technologist' M. W. Emmel, D.V.M., Veterinarian'
R. B. Becker, Ph.D., Dairy Husbandmana C. F. Simpson, D.V.M., Asso. Veterinarian
S. P. Marshall, Ph.D., Asso. Dairy Husb.3 L. E. Swanson, D.V.M., Parasitologist
W. A. Krienke, M.S., Asso. in Dairy Mfs.' Glenn Van Ness, D.V.M., Asso. Poultry
P. T. Dix Arnold, M.S.A., Asst. Dairy Husb.2 Pathologist
L. E. Mull, M.S., Assc. in Dairy Tech. G. E. Batte, D.V.M., Asso. Parasitologist
BRANCH STATIONS SUB-TROPICAL STATION, HOMESTEAD
NORTH FLORIDA STATION, QUINCY Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
J. D. Warner, M.S., Vice-Director in Charge D. O. Wolfenbarger, Ph.D., Entomologist
R. R. Kincaid, Ph.D., Plant Pathologist Francis B. Lincoln, Ph.D., Horticulturist
L. G. Thompson, Ph.D., Soils Chemist Robt. A. Conover, Ph.D., Asso. Plant Path.
W. C. Rhoads, M.S., Entomologist Milton Cobin, B.S., Asso. Horticulturist
W. H. Chapman, M. S., Asso. Agron. R. W. Harkness, Ph.D., Asst. Chemist
Frank S. Baker, Jr., B.S., Asst. An. Husb. J. L. Malcolm, Ph.D., Asso. Soils Chemist
Mobile Unit, Monticello W. CENT. FLA. STATION, BROOKSVILLE
R. W. Wallace, B.S., Associate Agronomist
Mobile Unit, Marianna William Jackson, B.S.A., Animal Husband-
R. W. Lipscomb, M.S., Associate Agronomist man in Charge2
Mobile Unit, Chipley RANGE CATTLE STATION, ONA
J. B. White, B.S.A., Associate Agronomist
Mobile Unit, Pensacola W. G. Kirk, Ph.D., Vice-Director in Charge
R. L. Smith, M.S., Associate Agronomist E. M. Hodges, Ph.D., Agronomist
D. W. Jones, B.S., Asst. Soil Technologist
E. M. Kelly, B.S.A., Asst. An. Husb.
CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Vice-Director in Charge CENTRAL FLORIDA STATION, SANFORD
W. L. Thompson, B.S., Entomologist
W. L. Tho sn, .S.A Entom ologist R. W. Ruprecht, Ph.D., Vice-Dir. in Charge
J. T. Griffiths, Ph.D., Asso. Entomologist W. Wilson, c.D., Entomologist
J. W. Wilson, Sc.D., Entomologist
R. F. Suit, Ph.D., Plant Pathologist
Ben. F. Whitner, Jr., B.S.A., Asst. Hort.
E. P. Ducharme, M.S., Asso. Plant Patho. en. F Whitner,JrB.S.A Asst. Hrt.
R. K. Voorhees, Ph.D., Asso. Horticulturist P Westgate, Ph.D., Asso. Hrt.
C. R. Stearns, Jr., B.S.A., Asso. Chemist
J. W. Sites, M.S.A., Horticulturist WEST FLORIDA STATION, MILTON
H. O. Sterling, B.S., Asst. Horticulturist C. E. Hutton, Ph.D. Agronomist'
J. A. Granger, B.S.A., Asst. Horticulturist H. W. Lundy, B.S.A., Associate Agronomist
H. J. Reitz, M.S., Asso. Horticulturist
Francine Fisher, M.S., Asst. Plant Path. FIELD STATIONS
I. W. Wander, Ph.D., Soils Chemist.
A. E. Willson, B.S.A., Asso. Biochemist Leesburg
J. W. Kesterson, M.S., Asso. Chemist
R. N. Hendrickson, B.S., Asst. Chemist G. K. Parris, Ph.D., Plant Path. in Charge
Wallace T. Long, M.S.A., Asst. Hort.
J. C. Bowers, B.S., Asst. Chemist Plant City
D. S. Prosser, Jr., B.S., Asst. Horticulturist A. N. Brooks, Ph.D., Plant Pathologist
R. W. Olsen, B.S., Biochemist
F. W. Wenzel, Jr., Ph.D., Supervisory Chem Hastings
Alvin H Rouse, M.S., Asso. Chemist A. H. Eddins, Ph.D., Plant Path. in Charge
L. W. Faville, Ph.D., Asst. Chemist E. N. McCubbin, Ph.D., Horticulturist
EVERGLADES STATION, BELLE GLADE Monticello
R. V. Allison, Ph.D., Vice-Director in Charge A. M. Phillips, B.S., Asso. Entomologist2
F. D. Stevens, B.S., Sugarcane Agronomist John R. Large, M.S., Asso. Plant Path.
Thomas Bregger, Ph.D., Sugarcane
J. W. Randolph, M.S., Agricultural Engineer J. R. Beckenbach, Ph.D., Hort. in Charge
W. T. Forsee, Jr., Ph.D., Chemist E. G. Kelsheimer, Ph.D., Entomologist
R. W. Kidder, M.S., Asso. Animal Husb. David G. Kelbert, Asso. Horticulturist
T. C. Erwin, Assistant Chemist E. L. Spencer, Ph.D., Soils Chemist
Roy A. Bair, Ph.D., Agronomist Robert O. Magie, Ph.D., Gladieli Hort.
C. C. Seale, Asso. Agronomist J. M. Walter, Ph.D., Plant Pathologist
N. C. Hayslip, B.S.A., Asso. Entomologist Donald S. Burgis, M.S.A., Asst. Hort.
E. H. Wolf, Ph.D., Asst. Horticulturist
W. H. Thames, M.S., Asst. Entomologist Lakeland
W. N. Stoner, Ph.D., Asst. Plant Path. Warren O. Johnson, B.S., Meterologist2
W. A. Hills, M.S., Asso. Horticulturist
W. G. Genung, B.S.A., Asst. Entomologist 1Head of Department.
S'In cooperation with U. S.
Daniel W. Beardsley, B.S., Asst. An. Husb. n Cooperative, other divisions, U. of F.
W. D. Hogan, M. S., Asst. Plant Path. 4 On leave.
INTRODUCTION --- -.--------------------- 5
HISTORICAL --- __ .--------------------- ----------------- -----6
LIFE HISTORY, HABITS AND TYPES OF DAMAGE ----- ---------------- 6
a) Corn earworm ----..----_ ..----.-___ ---------_- 6
b) Fall armyworm --_......----. _. _.---- -------- 9
c) Other insects ----------------------- 12
1. Sugarcane borer .--- __..__-- -- ---- ------------ 12
2. Fruit flies and scavenger beetles --------- --- --12
3. Corn-silk fly ----- ---------------------------- 15
4. Corn lantern fly-------------- --- ------ 15
5. Lesser cornstalk borer------ -------- ------------- 15
6. Cutworms ---- ------------------_ 15
7. Wireworms ----------- ---- 15
EXPERIMENTAL DATA, 1946-1948 15
a) Introduction ------------ ----------------------15
b) Vegetable Crops Laboratory, Bradenton --. ---------------- 17
c) Central Florida Experiment Station, Sanford --------------_ 19
d) Everglades Experiment Station, Belle Glade -- ------- __ 22
e) Discussion of experimental results ---- -------------------27
A BASIC CONTROL PROGRAM _.------------------------------------- 28
a) Selection and preparation of land --------------------------28
b) Planting the crop -- ----------------- 29
c) Insect control from germination to the silking period ----------30
d) Insect control during the silking period --_----- ________----32
RECOMMENDATIONS FOR QUICK REFERENCE - 23
a) Corn earworm --_____________ _------ 23
b) Budworms (fall armyworm and corn earworm) --------34
c) Cutworms -_--______-----_________ ----------_ 35
d) Wireworms ---_------------------------------- 35
e) Corn-silk fly ---_.---__---------------_---------- 35
f) Lesser cornstalk borer ------ --_------------_ --------_ 36
g) Corn lantern fly --.. ___ ______ __ __ __ __ ___----------- -------36
h) Sugarcane borer ----------________ ___----- 36
i) Fruit flies and scavenger beetles in tips of ears --- ----__ 36
PRECAUTIONS ....... .----------------------------_--_.----------------------- 36
SUMMARY ----------- -----....----------. .. .... ....----.._ 37
LITERATURE CITED ---..____ __... ___ ._.__________ ____------------------------------------__ 37
Budworms, Earworms and Other Insects
Attacking Sweet Corn and Green
Corn in Florida
By E. G. KELSHEIMER, N. C. HAYSLIP and J. W. WILSON
Entomologists, Florida Agricultural Experiment Stationst
Sweet corn is quickly taking its place in the agriculture of
Florida. It is an excellent crop to grow following fall crops or
for alternate-year cropping with other vegetables. The limiting
factors have been a lack of good varieties adaptable to Florida
conditions and difficulties encountered in the control of ear-
worms in the ears of corn.
Damage to the ears is caused mainly by the larvae of two
principal pests-the corn earworm and the fall armyworm. The
amount of damage sustained is influenced by (1) the density of
insect population, (2) the portion of the ear attacked, (3) the
natural resistance of the corn variety grown and (4) various
preventive measures which can be used. The time of year in-
fluences the density of the insect population.
Northern markets for Florida sweet corn are largely unde-
veloped, but are being developed rapidly. There has been a
prejudice against short-eared yellow-kernel sweet corn in
Southern markets, probably because most of the people in this
section prefer a large, long-eared white-kernel corn. Some of
this prejudice no doubt has been brought about by the fact that
sweet corn is so susceptible to damage from corn earworm, fall
armyworm and other larvae. Also, even when informed of con-
trol measures that will allow them to produce and market a
worm-free ear of sweet corn, growers object to a variety such as
Golden Cross Bantam because the stalks may be short and the
ears close to the ground, thus making harvest most laborious.
However, sweet corn can be grown economically in Florida.
A comprehensive comparison of varieties adapted to Florida is
being made for early publication elsewhere.
1 The authors are indebted to D. G. A. Kelbert for the photographs
used as illustrations, except one credited to N. C. Hayslip.
6 Florida Agricultural Stations
The use of oil injected in the silks for earworm control in
sweet corn was first suggested in 1939 by G. W. Barber of the
USDA Bureau of Entomology and Plant Quarantine. In 1940
he reported that the addition of pyrethrum to the oil improved
its killing effect upon larvae attacking corn (2)2. In 1944 he
published a comprehensive report of his work on many phases of
earworm control (5). Pepper and Barber (11) reported the use
I of dichloroethyl ether in mineral oil for corn earworm control
in sweet corn. Barber (3) reported the use of styrene dibromide
S as a substitute for pyrethrum in oil. Other workers (4, 6, 7, 12
S and 14) have since reported upon the efficacy of oil and oil plus
Watson and Tissot in 1942 (13) reported the use of lead arse-
nate and zinc arsenate dusted into the buds for budworm con-
trol, and they also used the same dust on the silks for earworm
With the release of new organic insecticides, the control con-
cept has changed considerably since the work reported herein
was first begun in 1942. Literature on the new organic is
voluminous, particularly for DDT. DDT was first used on sweet
corn in Florida by Russell (15). Since then many new materials
have been used which will be mentioned later.
Life History, Habits and Types of Damage
There are two main species of lepidopterous larvae which
cause the bulk of the damage to corn grown for marketing at the
milk stage. A third species is of lesser importance, and certain
other insects may cause damage under special conditions. It is
probably desirable to describe these insects in some detail so that
commercial growers will have a better understanding of each
The corn earworm, Heliothis armigera (Hbn.), is so abun-
dant in Florida that an ear of sweet corn not attacked by one or
more of these larvae is often difficult to find. This pest, common
also to cotton, tomato, corn, beggarweed, etc., prefers sweet corn
2 Italic figures in parentheses refer to "Literature Cited" in the back
of this bulletin.
Control of Budworms, Earworms and Other Insects 7
to any other host plant. The same insect is called the tomato
fruitworm and the cotton bollworm on these other hosts.
The early generation of corn earworm larvae on corn is
known as the budworm. There are other species of lepidopter-
ous larvae that cause similar damage and are also known as bud-
worms. Budworms usually appear when the corn plant is be-
tween its fifth and thirteenth leaves. None of the plantings
under observation has been free from attacks of one or more
species of budworm.
Corn earworm larvae hatch from yellowish-white, promi-
nently ribbed eggs which are approximately 1/20 inch in diame-
ter. These eggs are laid singly on the leaves of the corn plant.
Literature (10) records as many as 500 to 3,000 eggs per female
moth, the average being over 1,000. Eggs hatch in three or four
days, the time varying with the temperature. Newly hatched
larvae are about 1/25 inch in length, white or nearly so, with the
cervical shield and head black and body marked with numerous
black tubercles. Larvae feed on leaves and the immature tassel.
They later migrate to the silks and enter the ear through the
silk, or less frequently through the husk at the side and shank
end of the ear. Since these larvae may migrate to the ears over
a period of several days, control measures are difficult.
Approximately 17 days from the time of hatching are re
quired for larval growth in the early fall, during which time they
moult five times. When full grown the larvae are 11/ to 2 inches
long, and are of variable colors ranging from pink, green or
/ yellow to almost black. The side is marked with a longitudinal
stripe, consisting of a pale stripe edged above with black. There
is a dark stripe along the middle of the back divided longitudi-
nally by a narrow white line (see Fig. 1).
When full grown the larva chews out of the side of the husk
or crawls out of the tip of the ear and crawls or falls to the
ground. The mature larva burrows into the ground and enters
the pupal stage for approximately nine days. The pupa is about
% inch long, first green in color and later brown. The moth
which emerges has a wing expanse of about 112 inches. In
color it varies from a dusty yellow to grayish, with a dark-grey
to olive-green irregular line across the front wings. The hind
wings are light in color with irregular dark markings. The moth
is commonly observed flying during the day, and egg deposition
generally occurs in the late evening.
8 Florida Agricultural Stations
Fig. 1.-Corn earworm and its damage.
Control of Budwiorms, Earwzorms and Other Insects 9
The life cycle of an earworm generation of this insect is
exactly the same as for the budworm except that eggs are
generally deposited on the silk. There may be a complete genera-
tion within 29 days. There are usually seven generations a year
in southern Florida, since some of the moths remain active
during the winter. Since there is no general hibernation there
is no large seasonal emergence of moths.
The fall armyworm, Laphygma frugiperda (A. & S.), is the
second most important pest of sweet corn and green corn. This
insect also acts as a budworm, sometimes producing commercial
damage by causing stunted, barren stalks. This pest may be
found at all times of the year, but it is more prevalent in spring
plantings. It attacks other crops such as grasses, sweet potatoes,
Round, pinkish-white eggs are deposited in clusters on the
leaves of the food plants. The egg mass is covered with fine gray
scales from the body of the moth. According to Watson (13),
eggs are laid mostly on grasses in masses of 50 or more and
hatch in about 10 days, and caterpillars require about two weeks
to attain full size. The full-grown caterpillar is about 11/2 inches
in length and brown in color, with a narrow yellowish-grey
stripe along the middle of the back and a brownish-black stripe
along each side. A conspicuous inverted Y on the front of the
head is the characteristic most commonly used in its identifica-
tion. There are four black dots on each segment of the worm
(see Fig. 2). The adult moth has a wing expanse of approxi-
mately 11/4 inches. Front wings are grayish-brown with a
bluish-white spot crossed by a diagonal white bar near the tips
of the wing, while hind wings are pearl-white with a brownish
The fall armyworm, when numerous, may be as destructive
as the corn earworm, and it is harder to control because of its
habit of burrowing into the ear at any place it chooses, Prac-
tically all injury to the butt of the ear is caused by this pest. It
may occur alone or with the corn earworm in the ear (see Fig.
Most of the larvae of these two pests enter through the tip of
the ear, and these may be controlled by insecticidal measures. If
10 Florida Agricultural Stations
Fig. 2.-The fall armyworm.
Control of Budworms, Earworms and Other Insects 1
Fig. 3.-Top larva, corn earworm; lower larva, fall armyworm.
12 Florida Agricultural Stations
damage is slight, the damaged portion may be cut away. En-
trance into the ears through the side or butt end ruins the ear for
human consumption. The presence of the larvae, their excre-
ment, plus fermentation odors and perhaps molds, are all un-
desirable features from the viewpoint of the*consumer.
Sugarcane Borer.-The sugarcane borer, Diatraea sacchara-
lis (F.), (Figs. 4 and 5), is a minor pest of corn and may cause
slight damage in the form of broken tassels, broken stalks
weakened by tunneling of larvae, ears fallen to the ground due
to the shank being eaten partially through, or larvae tunneling
between the kernels. The pest has not been abundant on corn,
and is sporadic in its appearance. It is mentioned here because
it has so many habits suggestive of the European corn borer,
Pyrausta nubialis (Hbn.), a pest which has not yet been found
A common habit of the sugarcane borer is to bore into the
pith of the cob, hollow out a place, line it with silk and pupate.
The larva prepares an exit hole prior to pupating. If in the
stalk a thin membrane of plant tissue is left covering a hole al-
most cut through the tissue, if in the cob, the end is plugged with
frass. Eggs of the pest are round, flattened, and laid in clusters,
overlapping like shingles on a roof. They are white at first,
later changing to a brownish-orange color. According to Hollo-
way (9), eggs may be deposited on either side of the leaf. The
larva is about an inch long, the body white and covered with
regular brown spots. The head is also brown. The moth is the
color of dried brown corn leaves, with the forewings edged with
darker lines. The wing expanse is about one inch.
None of the control measures used against the corn earworm
and the fall armyworm have been successful against this insect.
Fruit Flies and Scavenger Beetles.-Any injury to the ear
of corn which exposes the kernel is almost sure to result in an
infestation of small brown beetles (Carophilus sp.) about 1/-inch
long. Corn in the milk stage ferments quickly when the kernel
is damaged and this probably attracts the beetles. Larvae of
3 An appeal is made to growers finding damage in cornfields having any
similarity to the above to send specimens of the insect causing the damage
to the Entomology Department, Agricultural Experiment Station, Gaines-
ville, Florida, for identification.
Control of Budworms, Earworms and Other Insects 13
Fig. 4.--Sugarcane borer.
14 Florida Agricultural Stations
Fig. 5.-Pupa of sugarcane borer in ear.
the fruit flies (Drosophila sp.) may infest ears, especially if the
the husk has been ripped apart to expose the tips. These insects
are an annoyance to merchants, and larval activity may cause a
high percentage of loss of ears where the tip is exposed.
Control of Budwiorms, Earworms and Other Insects 15
Corn-silk Fly.-The corn-silk fly, Euxesta stigmatias Loew,
(Figs. 6 and 7), an Otitid fly, at times prove a serious pest. It
has caused severe damage to sweet corn in the Everglades area.
Larvae causing the damage are about 3/8 inch long when mature.
Damage to the ear results from their working between the rows
of grain, entering the kernel at the base, hollowing out the kernel
and going on to the next kernel. Damage is generally to the tip
of the ear but sometimes they work on down the entire length.
In most cases the husk has to be removed before their presence is
noted. The adult is a small fly of a dark metallic green color
with black bands on the wings. The wings are often in motion
even when the fly is at rest. The adults are usually found around
the tassels and silks where moisture is present.
Corn Lantern Fly.-The corn lantern fly, Peregrinus maidus
Ashmead, is a slender yellowish-green insect about 1/6 inch in
length which collects in the buds and axils of the corn plant. It
is most destructive to young corn and large numbers sometimes
kill the plants. Corn that has reached the tasseling stage is not
severely injured by this insect.
Lesser Cornstalk Borer.-The lesser cornstalk borer, Elasmo-
palpus lignosellus (Zell.), at times is a serious pest of corn. The
larva is a bluish-green caterpillar that bores into the stem at the
surface of the ground and tunnels up and down in it, causing the
young plant to wilt and die. The larvae do not remain in their
tunnels except for feeding but are usually found in the soil in
a thin silken tube which is covered with sand and excrement.
Cutworms.-Several species of cutworms attack corn but no
attempt is made to separate the species. Damage is caused by
the larvae cutting off the young plants.
Wireworms.-Several species of wireworms attack corn. The
larvae are long, slender, hard, brown worms that feed below the
surface of the ground, boring into the plant and often causing it
to wilt and die. The larvae are most destructive to sprouting
Experimental Data, 1946-1948
Investigations on the control of insects attacking sweet corn
have been conducted at the Vegetable Crops Laboratory, Braden-
ton; Central Florida Experiment Station, Sanford; and Ever-
16 Florida Agricultural Stations
Fig. 6.-Corn silk fly damage to sweet corn.
Control of Budwuorms, Earworms and Other Insects 17
glades Experiment Station, Belle Glade. Results of these experi-
ments are reported in this section. Since these studies were
conducted individually at the various branch stations, slight
differences in methods of conducting experiments and evaluating
results occur. However, all experiments were so arranged that
they could be statistically analyzed. These data are the basis
for the recommendations made in this bulletin.
Vegetable Crops Laboratory, Bradenton
In the fall of 1946 a two-acre block of loana sweet corn grown
in a cover crop series experimental area received two ear treat-
ments, a 3 percent DDT dust and an oil-pyrethrum injection.
The dust plots received four applications directly to the silk, the
first when the silks were well out before pollination had taken
place and the remainder at three-day intervals for a total of four
applications. The oil series received one treatment when the
silks had wilted. There was a very heavy infestation of the fall
armyworm, amounting to 95 percent of the total worm popula-
tion. The remaining percent were the corn earworm. This was
not the usual proportion of species. The entire field was dusted
once for budworm with 3 percent DDT, using a crank duster,
when the corn was 12 to 15 inches high. It received two subse-
quent applications of 3 percent DDT dust with a puff duster when
the tassels were forming. The DDT killed small instar larvae of
the fall armyworm but was ineffective against 5th instar and
Fig. 7.-Close-up of corn-silk fly larvae.
18 Florida Agricultural Stations
mature fall armyworms. Mature larvae were rolled in the 3
percent DDT dust and pupated and produced normal moths.
There was little difference between the oil and dust treat-
ments in the percentage of marketable ears or in the number
absolutely worm-free. The percentage of ears with less than 1
inch of tips damaged for the dust-treated plots was 96.4 percent,
as compared to 94.5 percent for the oil-treated silks. The per-
centage of worm-free ears for the dust-treated silks was 85.9
percent, as against 83.3 percent for the oil-treated silks.
There was less sideworm (fall armyworm) damage in the
dust-treated ears, which is a rather important factor when we
consider the number of ears usually discarded because of side-
TABLE 1.-A COMPARISON OF Two SILK TREATMENTS FOR THE
CONTROL OF EARVIWORM.
Amount of Worm
Damage to Tips S p,
0 0 ai, a
3% DDT Dust ---_ 215 1,761 2,046 85.9 96.4 914
Mineral oil +
0.2% pyrethrum 242 1,803 2,164 83.3 94.5 917
There was no difference in weights of the ears from the two
treatments. Dust-treated ears weighed 914 pounds; those oil-
treated weighed 917 pounds. Dust-treated ears filled completely
to the tip, indicating no damage from the treatment. Oil-treated
ears receiving an application at the proper time filled to the tips;
otherwise from an inch to an inch and a half was not filled if the
silk was immature when oiled.
Truckers Hybrid sweet corn was planted in the spring of
1947. A number of organic sprays and dusts were compared
with mineral oil and 0.2 percent pyrethrins. The data are given
in Table 2. Practically all of the larvae attacking the ears were
Results of this experiment substantiated the previous one in
that four applications of 3 percent DDT dust applied at three-
day intervals reduced the sideworm (corn earworm) population
Control of Budworms, Earworms and Other Insects 19
very greatly. In this series all materials except mineral oil + 0.2
percent pyrethrins were applied four times at three-day intervals
as soon as silks appeared.
Three percent methoxychlor dust applied directly in the leaf
whorl was the only satisfactory budworm control in this test.
The budworms were mostly fall armyworms. DDT applied as a
dust or as a spray was ineffective against the later instars of
TABLE 2.-THE CONTROL OF EARWORM* IN CORN.
Treatment g" P 4 ,|
1. Check 13.9 10.7 32.2
2. Mineral oil + 0.2% pyrethrins -----52.1 43.4 20.6
3. Syndeet 1-400 spray ---------- 44.0 11.9 13.0
4. Chlordane 2 Lbs.-100 spray ._ ---- 28.3 9.4 25.4
5. DDT 50%W 3Lbs-100 spray ----------- 43.0 20.4 15.0
6. Piperonyl butoxide 1-800 spray--- 19.7 4.1 25.0
7. Piperonyl cyclohexenone 1-800 spray ----- 11.8 2.1 32.2
8. DDT 3% dust ---__ ---------------- 65.6 38.5 6.2
9. Chlordane 5% dust -..._....... ....._ ._ ..- .. 34.4 10.0 11.8
10. Methoxychlor 3% dust--------------- 66.3 40.2 5.4
11. Methoxychlor 2 Lbs-100 spray ---_- 27.1 8.6 25.9
12. Toxaphene 10% dust-- -.__-_--- 47.3 25.2 3.1
Difference necessary for significance ----- 13.7 12.9 12.4
*Heliothia armigera (Hbn.).
Central Florida Experiment Station, Sanford
During the spring of 1948 three series of experiments were
conducted at the Central Florida Experiment Station. Two of
these series of plots, one of which was used for dust materials
and the other for spray materials, were planted to Ioana sweet
corn March 16. The third series of plots, used for dust materials,
was planted to loana sweet corn March 31. These dates of plant-
ing are given here because it will be noted from Table 3 that
there is a considerable difference in the percent marketable ears
harvested from the two series of dust-treated plots. These dif-
ferencts are attributed to the higher population of corn earworms
occurring in the planting of March 16.
20 Florida Agricultural Stations
The plots were 6 rows wide and 60 feet long and each treat-
ment was replicated four times. Budworms failed to develop in
sufficient numbers to require treatment in the two plantings of
March 16. Two applications of 1 quart of 25 percent DDT emul-
sion to 100 gallons of water were made on May 10 and 17 for
budworm (Laphygma frugiperda (A. & S.)) control in the plant-
ing of March 31. Dust materials were applied in both series of
plots with a rotary-type hand duster beginning May 8 for the
March 16 planting and May 22 for the March 31 planting and con-
tinuing at three-day intervals for a total of four applications.
Spray materials were applied by means of a power sprayer
equipped with a six-row boom and fan-type spray nozzles. Spray
applications began May 10 and continued at three-day intervals
for a total of four applications.
Results presented in Table 3 are based on 50 ears of corn
harvested from the center four rows of each plot. The harvested
ears were shucked and separated into the following groups:
(1) worm-free, (2) less than 1 inch of the tip injured, (3) ears
showing more than 1 inch of tip injured and (4) with side injury
attributed to attacks by the fall armyworm.
In both dust-treated series of plots 5 percent DDT dust gave
best control of corn earworms. In the March 16 planting there
were no significant differences between the 5 percent DDT, 1.5
percent gamma isomer benzene hexachloride and 1 percent para-
thion dusts, but the 5 percent DDT was highly significantly
better than the other dust materials used in the March 31
planting. The 1 percent parathion dust-treated plots had the
lowest percentage of sideworm injury in the March 16 planting,
while the 5 percent DDT dust-treated plots had the lowest per-
centage of sideworm injury in the March 31 planting. In both
plantings ears harvested from the plots treated with 1.5 percent
gamma isomer dust mixed from the 25 percent gamma base had
a slightly objectionable flavor. For this reason benzene hexa-
chloride should not be used on sweet corn. No objectionable
flavor was noted in ears from any of the other treatments.
Plots receiving mineral oil with 0.19 percent pyrethrins in-
jected into the silks at the time the silks wilted were included
with the spray plots. This material gave the largest percentage
of worm-free ears of all the treatments. Of the spray treatments
the 50 percent wettable methoxychlor at 4 pounds to 100 gallons
of water gave the best earworm control. However, this material
Control of Budwiorms, Earworms and Other Insects 21
TABLE 3.-RESULTS FROM TREATMENTS OF IOANA SWEET CORN AT SANFORD
WITH VARIOUS INSECTICIDES FOR THE CONTROL OF CORN EARWORM*.
Treatment 4 ,
"0"1 Q 5
Check ------------------- --- 10.5 2.0 56.8
5% DDT --- ------------ ------- 27.5 19.5 59.3
5% Methoxychlor ----- ---- 17.5 0.5 30.5
1.5% gamma isomer from high gamma ---- 21.0 5.0 27.6
1% Parathion ------------- ----- 27.0 2.0 17.7
10% Toxaphene --------------------- 19.5 1.5 41.3
5% Chlordane ---------- ---------- 17.5 1.5 54.5
Differences required for significance (19-1) 7.92 4.20 10.79
Check __------------------ 28.7 6.1 8.0
0.19% pyrethrins in mineral oil 80.5 64.7 1.5
25% DDT emulsion, 1 qt. to 100 gal. .---- 32.6 8.8 13.4
25% DDD emulsion, 1 qt. to 100 gal. --.... 37.5 21.0 7.6
50% Wettable methoxychlor, 4 lb. to 100 gal. 54.7 28.9 5.5
25% Wettable parathion, % lb. to 100 gal. 53.1 29.6 5.1
48% Chlordane emulsion, 1 qt. to 100 gal. -_ 49.6 26.3 3.1
Differences required for significance (19-1) 13.76 14.38 4.02
Check ------------- 11.9 0 49.1
0.25% Rotenone -- --------------
0.5% Piperonyl cyclohexanone --- 12.2 0.5 51.8
0.05% Pyrethrins ---- --
0.5% Piperonyl cyclohexanone -----
0.05% Pyrethrins -- ----------------- 16.7 0.5 48.8
0.125% Rotenone -----
0.5% Piperonyl cyclohexanone --- 12.9 0.5 42.9
5% DDT -- -----54.5 29.9 3.8
5% Methoxychlor --- --- ---------- 24.8 1.9 26.7
1.5% gamma isomer from high gamma .--- 20.2 1.9 28.5
1% Parathion -.-------------------- 32.9 7.6 26.1
20% Toxaphene ------------ 23.5 2.9 20.5
5% Chlordane -.-...---------------------------- 21.0 3.7 18.5
0.5% Parathion and 2.5% chlordane -- 34.9 5.4 27.8
Differences required for significance (19-1) 3.46 1.99 7.09
*Heliothis armigera (Hbn.).
**All of the dusts except those containing piperonyl cyclohexanone were mixed from
concentrates supplied by commercial formulators in the laboratory dust mixer. Pyrax was
used as a diluent.
First dust and spray-treated plots were harvested May 24 and 25, 1948. Second dust-
treated plots were harvested June 4, 1948.
22 Florida Agricultural Stations
was not significantly better than 1/2 pound of 25 percent wettable
parathion and 1 quart of 48 percent chlordane emulsion to 100
gallons of water. The-population-Qobudworms was not high, as
only 8 percent of the-ears-from the check plot showed side injury.
Everglades Experiment Station, Belle Glade
U. S. 34 sweet corn was planted in the spring of 1946 to test
certain spray and dust formations against the fall armyworm
attacking the buds of corn plants. A single treatment was ap-
plied 21 days following planting, using a wheelbarrow type
power sprayer at 200 pounds pressure to apply the sprays and a
rotary hand duster to apply the dust formulations. A list of the
various formulations of DDT used is included in Table 4, with
control data showing the superiority of sprays over dusts for
TABLE 4.-THE EFFECT OF SPRAY AND DUST FORMULATIONS OF DDT ON
FALL ARMYWORMS IN THE BUDS OF SWEET CORN*.
Average Percent of
Treatment Buds Damaged 8 Days
DDT emulsion-1 pound DDT per 100 gal. .--. 4.4
DDT wettable-1 pound DDT per 100 gal. ---.--- 6.4
DDT dust-3 percent in sulfur __-----------_ 22.1
DDT dust-3 percent in talc _------ ____- 25.5
DDT dust-1 percent in talc _---------- 43.7
Check, not treated -------- ----------- 43.8
Difference required for significance --------- 4.9
*Data of Dr. W. D. Wylie.
In the Spring of 1948 a planting of Big Joe field corn was
used for comparing several spray and poisoned bait formulations
for the control of fall armyworms in the buds of the corn. Spray
treatments were applied by a power sprayer with a three-nozzle
boom operating at 200 pounds pressure and delivering about 125
gallons of spray per acre. Baits were applied by hand, dropping
a small pinch into each bud. The first applications were made
when the corn was 16 inches tall, at which time almost 100
percent of the buds were infested with worms. A second treat-
ment was applied six days following the first. Control data were
obtained four days following each treatment. The list of ma-
trials applied and amount of control obtained are included in
Control of Budworms, Earworms and Other Insects 23
Tables 4 and 5 show that poisoned baits were most effective
in budworm control, followed by sprays and dust in the order
named. This order of effectiveness has been generally consistent
in all of the trials conducted during the last three years. On very
young corn, poisoned baits have not been as effective as on larger
corn. For example, a cryolite-corn meal bait applied to corn 21
days after seeding was inferior to DDT sprays but was superior
to cryolite dust or spray. The same type of bait applied to corn
58 days after seeding was superior to DDT sprays, with almost
complete eradication of budworms. As the worms migrate from
the leaves into the buds and feed deeper into the whorl, poisoned
baits become more useful. Baits applied to large corn from air-
planes may give effective control of budworms, but this method
of application is somewhat inferior to hand applications.
TABLE 5.-THE EFFECT OF SPRAYS AND BAITS FOR THE CONTROL OF
FALL ARMYWORMS IN THE BUDS OF FIELD CORN.
of Buds Damaged
W 4-> 0
Material Applied Formation
DDT-50 percent --- 2 lb. per 100 gal. 29.7 4.6
Methoxychlor-50 percent -_ 2 lb. per 100 gal. 40.2 8.9
DDD-50 percent- -_ 2 lb. per 100 gal. 32.7 9.5
Parathion-15 percent _...-----1 lb. per 100 gal. 36.3 9.3
Parathion-15 percent -_--_---.... lb. per 100 gal. 39.7 11.4
HCH-6% gamma isomer ------ 4 lb. per 100 gal. 33.6 13.5
Toxaphene-25 percent __--- 4 lb. per 100 gal. 28.5 7.4
Chlordane-50 percent ---------- 2 lb. per 100 gal. 22.9 7.3
DDT-wheat bran bait ------ 5 percent DDT 35.5 6.5
Chlordane-wheat bran bait ---- 5 percent chlordane 19.0 2.8
Parathion-wheat bran bait 1.5 percent parathion 13.4 0.0
Check, not treated ____ __-- -_ ___ 95.3 80.3
Difference required for significance 8.7 8.2
Sprays have consistently given satisfactory budworm control
when the applications were properly timed and coverage was
thorough. On young corn numerous worms are scattered over
the leaves and in the buds. All leaves and buds must be thor-
oughly covered with spray if a high percentage of these worms
24 Florida Agricultural Stations
are to be killed. On larger corn, after the worms have migrated
into the buds, most of the spray should be directed into the whorl.
A power sprayer is needed for best control. It is difficult to obtain
maximum control with a knapsack sprayer, requiring very care-
ful and thorough operation. The use of a power sprayer with
three nozzles per row operating at about 300 pounds pressure and
delivering 75 to 125 gallons of spray per acre (depending upon the
size of the plants) will give good control of budworms. Results
obtained with dusts indicate that they are inferior to baits and
sprays against budworms. Ground-powered dusters are fairly
effective and may be used if spraying is not possible. The dust
lso should be directed into the buds.
As noted in Table 5, several insecticides have been found ef-
fective against budworms in corn. The grower should first make
certain that he has equipment suitable for thorough treatment
land then select the material which fits his particular need. Cost
of the insecticide would certainly be one consideration. If crop
remains are to be fed to livestock, methoxychlor should be used,
since it is reported to be less toxic than DDT to warm-blooded
animals. Those with small acreages which do not justify the
purchase of power sprayers may elect to spray or dust young
corn with hand equipment and use a poisoned bait after the
worms have migrated into the buds.
Corn earworm control studies have provided the basis for
evaluation of a number of insecticidal dust and atomized oil
spray formulations applied to the silks. Data obtained from two
of these experiments are reported.
A planting of loana sweet corn was made in the spring of 1947
to test methods for control of corn earworms. The dusts were
applied with rotary hand dusters at the rate of approximately
35 pounds per acre for each application, and the oil-pyrethrum
injection treatment was applied with a hand force oiler at the
rate of .% cc. per ear. A light mineral oil containing 0.19 percent
pyrethrins was used. The first silks were observed May 2 and
the dust applications were made April 30, May 3, 7, 12 and 16.
One treatment was made on the oil injection plots on May 12.
Twenty-five ears of corn were obtained from each plot, giving a
125-ear sample from each treatment to determine insect damage.
The fall armyworm, corn earworm and the corn-silk fly were
present, and the amount of damage caused by each of these pests
was recorded. These data are included in Table 6.
Control of Budworms, Earworms and Other Insects 25
TABLE 6.-EFFECTIVENESS OF VARIOUS INSECTICIDES IN CONTROLLING
SWEET CORN PESTS DURING THE SPRING OF 1947*
From a Sample of 125 Ears
Number of Ears With
Less Than 2 Inches of c
Tip Damaged By: 1 E
Treatment | o
Chlordane-5 percent .------.------------... 112 110 | 121 28
Toxaphene-5 percent .------- ---- | 100 112 121 14
DDT-5 percent; Benzene hexachloride
0.36 percent gamma isomer _---------- 95 112 122 34
DDD-5 percent .----- ----.--..-.-- -. .------. | 90 115 121 44
Benzene hexachloride-1 percent
gamma isomer -__._-. -.. _--------------. 104 103 118 14
DDT-5 percent ..------. --. .....----------. 90 110 118 41
Pyrethrins (0.19 percent)- I
mineral oil -_ -------------.................-.... 83 120 102 99
DDD-5 percent; piperonyl butoxide--
1 percent -___.- ----------- .----_ 72 107 123 29
Check, not treated ----_ ...----_. 70 100 98 14
Difference required for significance. Not sign.1 11 13 14
*Data of Dr. W. D. Wylie.
TABLE 7.-RESULTS OF CORN EARWORM CONTROL STUDIES CONDUCTED
DURING SPRING OF 1948.
Amount of Damage Due
Treatment to Corn Earworms
Chlordane-3 percent --------------- 199 6
Methoxychlor-3 percent ----- ------- ------- 194 3
DDD-5 percent -._. ........----------- -- ....141 23
DDT-5 percent _- --------------- 116 39
Toxaphene-5 percent ------- ---------------- 203 2
Parathion-1 percent ---------------- 146 21
DDT-oil based-2.7 percent DDT** -----I 0 100
Check, not treated __---- ------------------ 218 1
Difference required for significance------------ 23
"*A scoring system was used as follows: 0-no worm damage; 1-less than one inch of
tip damaged; 2--one to two inches of tip damaged; 3--over two inches of tip damaged.
Total score for 100 ears shown.
"**Applied as an atomized spray on the silks.
26 Florida Agricultural Stations
An experimental planting of loana sweet corn designed to
compare the newer insecticide dusts and one atomized oil-based
DDT spray was made in the spring of 1948. Dusts were applied
to the silks at the rate of about 35 pounds per acre with a rotary
hand duster. The oil-insecticide plots were treated with a
hydraulic aerosol hand sprayer delivering 0.6 cc. of spray per ear
in the silk area from each side of the row. The first treatments
were applied when the silks began to show, and additional appli-
cations were made at 3-day intervals until a total of 6 treat-
ments were applied. The corn was harvested on two dates and
a sample of 20 ears of corn from each plot was examined for corn
earworm damage during the first harvest. A record of worm
damage under the various treatments is contained in Table 7.
Table 6 shows results obtained in the spring of 1947 where
the corn-silk fly, the corn earworm and the fall armyworm were
present in damaging numbers. The corn-silk fly infestation was
so variable that statistical differences could not be demonstrated.
However, it appears that some of the treatments may have been
effective in reducing the damage due to the pest. In the corn ear-
worm data the differences between treatments are much more
pronounced on the basis of worm-free ears than on the basis of
ears with less than 2 inches of the tips damaged. Based on
worm-free ears of corn, the oil-pyrethrum was better than any of
the dusts. Of the dusts DDT and DDD appeared to be the best,
while toxaphene and benzene hexachloride seemed to be least
effective. In taste tests all treatments were satisfactory except
the benzene hexachloride, which imparted an objectionable taste
to the corn.
Table 7 records the results of the spring 1948 corn earworm
experiment. Using the scoring system outlined, the 5 percent
DDT dust was superior to the other dust treatments in reducing
earworm damage. Five percent DDD and 1 percent parathion
dust were inferior to the 5 percent DDT dust but were superior
to 3 percent chlordane, 3 percent methoxychlor, 5 percent toxa-
phene and the check.
Complete absence of earworm damage in the atomized oil-
based DDT spray plots was a striking contrast to the best dust
treatment, which produced only 39 percent worm-free ears.
Six atomized DDT-oil treatments produced definite injury to the
tips of the ears by preventing kernel formation for from one to
three inches on many of the ears. This tip damage was quite
Control of Budworms, Earworms and Other Insects 27
similar to damage resulting from mineral oil-pyrethrum treat-
ments. Later studies with atomized oil-based insecticide sprays
indicate that excessive tip damage may be avoided by fewer
applications and proper timing. This problem is receiving active
study at the Everglades station and the atomixed oil treatment
is not recommended until these studies are complete.
Discussion of Experimental Results
In the three sections of experimental data presented, most of
the more promising control methods and materials have been
evaluated. The rapid revolution in insect control makes neces-
sary a more or less continuous research program to improve the
control of insects attacking corn, or any other crop. Certain
differences in control obtained with similar treatments at the
three branch stations serve to demonstrate the complexity of the
problem of insect control. By combining and analyzing the re-
search data, a recommended control program is presented for
insects attacking sweet corn.
Budworms have been controlled satisfactorily with a number
of insecticides, in bait, spray and dust formulations. Poisoned
baits have given the most effective control when applied by hand
to the buds. However, cost of application limits this method to
small acreages. Sprays applied with power sprayers have proved
most satisfactory to commercial sweet corn producers and are
superior to dusts. Ground- powered dusters have been fairly
effective when the treatments were thorough and properly
timed. DDT, methoxychlor, DDD, parathion, toxaphene and
chlordane have all given good control of fall armyworms in corn
buds. DDT emulsion is recommended for most purposes because
it (1) has been thoroughly tested, (2) is relatively inexpensive
and (3) is comparatively safe to apply. Methoxychlor should be
used for budworms if the crop remains are to be fed to livestock.
Oil-pyrethrum injection dusts and sprays have each given
fairly satisfactory control of corn earworms in certain instances.
DDT, methoxychlor, parathion, chlordane and toxaphene have
shown promise in at least one test. The oil-pyrethrum injection
method has consistently given the best control of corn earworms.
However, cost of application and time required for making the
treatment limit its use. Dust formulations have been most
thoroughly tested and application with ground-powered dusters
and airplanes make this method of treatment most satisfactory
28 Florida Agricultural Stations
at present. Spray formulations offer definite promise where high-
clearance sprayers are available. DDT has been consistent in
giving good earworm control except in cases where the infesta-
tion is extremely severe. The other materials have been erratic
in their control, giving satisfactory control in one test and poor
control in others. Benzene hexachloride imparted a flavor to
corn and is not to be recommended. Parathion is new and ef-
fective, but its use should be discouraged until more is known
concerning its safety on edible plants.
A Basic Control Program
Since-insect control plays such an important part in the suc-
cessful production of sweet or green corn that the grower should
make careful plans for meeting the insect problems before they
arise. The following program is designed to guide the sweet
corn grower in insect control as the crop develops, beginning
with the selection and preparation of land and carrying through
the harvest period. Certain control methods will necessarily
differ for the home gardner and the commercial producer. Where
these differences occur, recommendations are given for each.
Selection and Preparation of Land
To reduce damage to corn caused by insect feeding the crop
must (1) give a good and rapid germination and (2) grow vigor-
ously. A poor stand of corn suffers more from wireworm and
cutworm damage, since the feeding of these pests further re-
duces the stand and is more likely to result in an unprofitable
crop than would be the case if the original stand were good. If
corn seed is slow in germinating the insects present in the soil
have more time to feed upon it and the loss is usually more severe
than in corn plantings where the seeds germinate rapidly. Vigor-
ously growing corn plants often support an infestation of bud-
worms and make a good crop despite their presence, while slowly
growing plants are usually killed by budworms because the
plants produce plant material more slowly than the worms feed.
It becomes apparent that the selection of good productive soil
with adequate water control, as well as thorough land prepara-
tion, are important factors in making a crop more tolerant to
It is not advisable to plant corn in an area where wireworms
are known to be present in large numbers. By checking behind
Control of Budworms, Earworms and Other Insects 29
the plow as it turns the soil the grower can determine whether
wireworms are present. A method of determining the presence
of wireworms in soil after it is plowed consists of placing Irish
potatoes in the soil with stakes placed as markers. If these
potatoes are left for about five days and then dug and examined
wireworm damage will indicate an infestation if the pests are
present in large numbers. A third method of determining the
presence of wireworms consists of a hardware cloth screen
made into a sifter. Samples of soil taken over the farm may be
sifted and any wireworms present may be found.
Cutworms feed upon a wide variety of weeds and grasses
and are often present in soils with weed and grass cover crops.
When the land is plowed the weeds and grass are destroyed but
the cutworms remain in the soil for some time following cultiva-
tion. If the soil is prepared well in advance of planting many of
the worms will be starved out. However, if the corn is planted
immediately following plowing, the cutworms may destroy the
entire crop within a few days after it germinates. It is therefore
recommended that the land be prepared as far ahead of planting
as is possible, with one and two months before seeding being
Planting the Crop
To produce a high yield of good quality corn it is necessary to
use a fertilizer formula which fits the particular soil type where
the corn is to be grown and to apply this fertilizer in ample
quantities to insure vigorous growth. Fertilizer formula, rate
and placement recommendations may be obtained from the
Florida Agricultural experiment Station. If corn must be
planted where wireworms are present, an insecticide may be
mixed with the fertilizer and applied to the soil before seeding.
This method of wireworm control is in the experimental stage,
but preliminary work4 indicates that about 2 pounds of technical
chlordane per acre applied with the fertilizer before seeding will
reduce damage caused by wireworms. The best control was ob-
tained where the fertilizer-insecticide was placed in bands below
the seed. This treatment has not proven adequate for cutworm
4Wireworm control studies conducted by W. H. Thames, Assistant
Entomologist, Everglades Experiment Station.
30 Florida Agricultural Stations
Insect Control From Germination to the Silking Period
One of the most critical problems in sweet corn production is
in protecting the stand from the time the seed germinate until
the corn reaches about 8 inches in height.
Cutworms.-In many cases cutworms are present in the soil
when the seed is planted, and a moderate infestation of these
pests is capable of destroying entire plantings of young corn if
control measures are not initiated. The first evidence of cut-
worm damage is rather deceiving, with a tiny corn plant cut here
and there appearing far less serious than is actually the case.
These worms feed upon several plants each night and soon merge
into migrating colonies where the infestation is heaviest. The
second stage of this cutworm damage appears as small irregular
areas in which all of the plants have been destroyed. From
this period to total destruction of the field is only a matter of a
few days, since the worms assume true armyworm tactics of
feeding night and day in large colonies. It is recommended that
the grower check the entire planting closely for cutworm damage
as soon as the corn germinates, and make subsequent inspections
every other day until certain no cutworms are present. If cut-
worms are found, a poisoned bait of 3 pounds Paris green per 100
pounds wheat bran with water, molasses or SAE-20 oil added
as a sticker should be applied at once at the rate of 25 pounds per
The bait should be broadcast evenly over the area in the late
afternoon, and may be applied by hand or by airplane. If the
bait is to be applied by hand, water or molasses may be added as
a sticker at the rate of 1 gallon of molasses per 100 pounds bran
plus enough water to moisten slightly but not wet the bait.
Moist baits should be applied soon after they are made. If the
bait is to be applied with an airplane, 1 gallon of SAE-20 oil may
be substituted as a sticking agent. Do not apply the bait if a
rain is expected that night, since heavy rains destroy the ef-
fectiveness of poisoned baits. Do not throw large amounts of
bait on corn plants, or burning will result.
A 5 percent toxaphene or 5 percent DDT dust may be applied
in the late afternoon at the rate of 35 pounds per acre in place of
baiting. Dusts should be applied when the air is still. Growers
in the Everglades have controlled cutworms attacking young
corn with 1 to 11/2 quarts of 25 percent DDT emulsion or 4 pounds
of 50 percent wettable toxaphene per 100 gallons of water ap-
Control of Budworms, Earworms and Other Insects 31
plied at about 300 pounds pressure, using 3 nozzles per row and
delivering about 100 gallons of spray per acre. The home
gardener may prefer to scratch out the worms and destroy them.
In the Bradenton area 5 percent chlordane applied as a dust
in the row has given good cutworm control. Wet weather does
not affect its killing power.
Wireworms.-If these pests are present after the seed germi-
nates, wilted plants will be seen in the field. No control is known
after the crop is planted.
Lesser Cornstalk Borer.-This insect's presence also appears
in the form of wilted plants. Early treatments with DDT or
chlordane have reduced damage.
Budworms.-The presence of budworms is first noted as egg
masses or feeding of young worms on the leaves of the corn.
After feeding upon the leaves the worms migrate into the buds,
where they remain until they mature and go into the soil to
pupate. The first budworm treatment should be applied when
feeding signs appear on the leaves. Later applications will be
necessary at intervals, depending upon the severity of the in-
festation and weather conditions. A spray containing 1 quart of
25 percent DDT emulsion or 2 pounds of 50 percent wettable
DDT powder per 100 gallons of water is recommended for bud-
worm control. A good spreader-sticker should be added to the
spray for best results.
A power sprayer utilizing three nozzles per row to apply 75
to 125 gallons of spray per acre at about 300 pounds pressure will
give efficient coverage. As the plants become larger the amount
of spray should be increased from 75 to 125 total gallons per acre.
One nozzle should direct the spray into the buds from above and
the other two nozzles should be directed from each side of the
plants into the upper leaves. Spray applications at 10-day to
two-week intervals usually are sufficient for good control. How-
ever, under heavy budworm attacks it is necessary to spray once
each week. If high-clearance sprayers are used it is advisable
to spray until the corn reaches the tasseling stage. Sprayers
with limited clearance should be used as long as possible, making
a thorough cleanup treatment just before the crop becomes too
tall to use the sprayer.
If budworm treatments are necessary after the eorn is too
high for ground equipment, an airplane may be used to apply 35
pounds of 5 percent toxaphene or 5 percent DDT dust per acre;
32 Florida Agricultural Stations
or a poisoned wheat bran bait containing 5 percent toxaphene
may be applied at the same rate per acre. It is important to have
the corn free of budworms at tasseling time, since the worms
migrate into the young ears and cause heavy damage. After
feeding into the ears these worms cannot be controlled.
Producers of small acreages of corn and home gardeners may
use a knapsack or compression-type sprayer for budworm con-
trol. The DDT spray should be directed into the buds and from
each side of the plants to get adequate coverage. This means
three trips to each row with a single-nozzle sprayer. Dusting is
equal to hand spraying and a 5 percent DDT dust may be applied
at weekly intervals with a rotary hand duster. The dust should
be applied at about 35 pounds per acre and directed into the buds.
After the plants have reached about two feet or more in height
budworms may be controlled with poisoned baits. A 5 percent
toxaphene-wheat bran bait has been effective when a small pinch
was applied to each bud.
Insect Control During the Silking Period
Corn Earworm.-If budwords are present when the tassels
begin to show, applications of 5 percent DDT or 5 percent toxa-
phene dust should be made before the silks appear to control
these pests before they migrate into the ears. However, if no
budworms are present the first treatment with DDT should be
applied when the silks begin to appear and subsequent applica-
tions should be made at three-day intervals until the silks have
turned brown. This requires from four to six applications. Five
percent DDT dust is recommended at the rate of 35 pounds per
acre with ground-powered dusters, if available. The dust should
be directed at the silks. Airplanes may be used for applying the
dust if ground equipment is not available. Small acreages may
be dusted with a rotary-type hand duster. Applications should
be made when the air is calm, and late afternoon treatments
appear more effective than early morning applications.
The most effective method of controlling corn earworms has
been an oil-pyrethrum injection into the tips of the ears when
the silks wilt but before they turn brown. This method is rather
laborious and slow, and consequently is not used extensively by
large growers. For growers of small plots this method would
give a much higher percentage of worm-free ears than dusting.
A white mineral oil containing about 0.2 percent pyrethrins should
Control of Budworms, Earworms and Other Insects 33
be injected into the tips of the ears at the rate of %/ CC. per ear
with a force oiler equipped with an adjustment screw for regulat-
ing the amount of oil applied. This treatment must be carefully
timed to prevent damage to pollination. One treatment is suf-
ficient if the corn silks evenly. Applications made too early inter-
fere with kernel formation and those made too late will not con-
trol the worms. If the corn silks unevenly two applications may
Corn-silk Fly.-Check the corn plantings when the silks begin
to show for the presence of the adult flies on the leaves and stalks
and around the silks. If the flies are present, apply 35 pounds
per acre of 3 percent chlordane dust. This may be mixed with 5
percent DDT. One chlordane treatment is often sufficient to kill
the adul flies. The treatment should be made as soon as the silks
open in order to destroy the flies before they deposit eggs on the
Recommendations For Quick Reference
The following recommendations are brief statements on
methods and materials for insect control. A more detailed ac-
count may be found in the Basic Control Program section.
1. Check buds and tassels when tassels begin to show. If
worms are present treat with 35 pounds per acre of 5 percent
DDT or 5 percent toxaphene dust before silk appears. If a high-
clearance sprayer is available apply 150 gallons of spray per acre
containing 1 quart of 25 percent DDT emulsion or 4 pounds of
25 percent toxaphene per 100 gallons in place of dusting. Use
three nozzles per row, one over the tassels and one directed into
each side of the row.
2. When first silks appear apply 35 pounds of 5 percent DDT
dust per acre and repeat at three-day intervals until silks turn
brown. Four to six applications will be necessary. Ground-
powered dusters directing the dust at the silks from each side of
the row are most effective. Airplanes may be used if ground
equipment is not available. Silks must be kept thoroughly
covered with dust for good control.
Home Gardeners and Growers of Small Acreages.-Two alter-
nate procedures are suggested, depending upon type of material
and equipment available.
34 Florida Agricultural Stations
1. Check buds and tassels when tassels begin to show. If
worms are present treat with 35 pounds per acre of 5 percent
DDT or 5 percent toxaphene dust before silks appear. A rotary-
type hand duster directing the dust downward from the tops of
the tassels into each side of the rows will give good coverage.
When first silks appear apply 35 pounds of 5 percent DDT dust
per acre and repeat at three-day intervals until silks turn brown.
Four to six applications are necessary. A rotary-type hand
duster directing the dust at the silks from each side of the rows
is most effective.
2. The alternate method is to inject a small amount of mineral
oil containing 0.2 percent pyrethrins into the tip of each ear
through the silks. Care should be exercised to insure that only
ears with the silks beginning to wilt are treated with this ma-
trial. This means that usually a field will have to be gone over a
second time, two or three days after the first treatment, to treat
ears not far enough developed to be treated the first time. The
timing of the application of this material must be accurate.
When the application is made too early the oil will interfere with
pollination, resulting in a poorly filled ear. When the application
is delayed too long the earworms will have already penetrated the
silks and entered the ear. The treatment gives a high percentage
of worm-free ears.
Budworms (Fall Armyworm and Corn Earworm)
1. First treatment should be applied when leaf feeding is ob-
served, and at one- to two-week intervals, depending upon the
degree of infestation.
2. One quart of 25 percent DDT emulsion or 2 pounds of 50
percent wettable DDT powder per 100 gallons of water plus a
spreader-sticker is recommended-applied with a power sprayer,
2 nozzles per row, 300 pounds pressure and 75 to 125 gallons
spray per acre. Apply enough spray to create slight run down
into the buds for efficient control.
3. After the corn is too high for ground equipment the follow-
ing is recommended:
(a) 5 percent DDT or 5 percent toxaphene dust applied at 35
pounds per acre, or
(b) 5 percent toxaphene-wheat bran bait applied at 35 pounds
Control of Budworms, Earworms and Other Insects 35
Home Gardners and Growers of Small Acreage.-
1. One quart of 15 percent DDT emulsion or 2 pounds of 50
percent wettable DDT powder per 100 gallons of water applied
with knapsack sprayer with nozzle directed into the bud and
from each side of row. Spray each week, or
2. Thirty-five pounds per acre of 5 percent DDT dust applied
with rotary hand duster each week when air is calm.
3. After the corn is two feet or taller 5 percent toxaphene-
wheat bran bait may be applied by hand into the buds of corn.
A small pinch per plant gives good control of fall armyworms.
4. Methoxychlor 3 percent dust is recommended for those
growers intending to feed crop remains to fattening livestock and
to dairy cattle.
1. Make frequent checks for cutworm damage as soon as corn
2. Control cutworms at once on young corn.
(a) Broadcast 25 pounds per acre of 3 percent Paris green-
wheat bran bait in late afternoon. Avoid getting the bait on the
plants as it will burn, or
(b) Spray young corn with 1 quart DDT emulsion or 4
pounds of toxaphene (25% wettable) per 100 gallons of water, or
(c) Dust with 35 pounds of 5 percent toxaphene or 5
percent DDT in late afternoon or night.
(d) Home gardeners may scratch out and destroy worms
where cut plants occur.
1. Do not plant corn on land known to be heavily infested
with wireworms. If a light infestation occurs mix chlordane
with fertilizer and apply in bands below the seed at the rate of 2
pounds technical chlordane per acre before planting the seed.
2. No control is known after the crop is planted. Home
gardeners may locate wilted plants and scratch out the wire-
worms and destroy them.
If the adult flies are present in the field when the first silks
begin to appear apply 3 percent chlordane dust at the rate of
35 pounds per acre, or spray with 2 pounds 50 percent chlordane
wettable powder per 100 gallons water. The chlordane may be
36 Florida Agricultural Stations
mixed with DDT, since the regular corn earworm treatments
should be in progress during this treatment.
Lesser Cornstalk Borer
No satisfactory control is known. Chlordane may reduce
damage caused by this pest. Spray or dust the bases of the
Corn Lantern Fly
Spray with 4 pounds 25 percent toxaphene per 100 gallons
water. This will also control budworms. Repeat when necessary.
No control is known on corn. Toxaphene has been effective
on sugarcane and may reduce damage on corn.
Fruit Flies and Scavenger Beetles in Tips of Ears
These insects invade corn infested with earworms or damaged
by birds or varieties with short and loose husks. Select varieties
with rather long, tight husks extending beyond the tips of the
ears and maintain control of earworms and birds.
Work conducted by the USDA Bureau of Entomology and
Plant Quarantine has shown crops treated with DDT to be unsafe
for feeding to dairy and beef cattle. It has been suggested by
the bureau that the analogs of DDT, such as methoxychlor and
TDE (DDD), are less toxic than technical DDT and may reduce
the possible hazards for use on products that are to be used for
food or feed. Until more information is available crop remains
that have been treated less than 30 days prior to harvest with
DDT, chlordane and toxaphene should not be used for dairy or
beef cattle feed.
All of the insecticides recommended in this bulletin for the
control of insects attacking corn are poisons and should be
handled as such. Persons applying these materials in the field
should avoid the dust or mist from the spray. If they acci-
dentally get on exposed parts of the body, insecticides should be
removed immediately by thorough washing with soap and water.
After the application of the insecticide is completed operators of
dusting and spraying machines should bathe and change to clean
Control of Budworms, Earworms and Other Insects 37
Never use a duster or sprayer that has copper fungicide in it
for the application of insecticides to corn. This also applies to
the hopper of a plane. Corn is very sensitive to even small
amounts of copper. Typical copper burn is similar to scorching
A basic insect control program is offered as a guide to the
home and commercial grower of sweet corn and green corn from
preparation of soil to harvest. The use of paris green bait, 5
percent DDT, toxaphene or chlordane dust is so necessary for
control of cutworms that it may be considered as a cultural prac-
tice. Budworm control before tasseling is very important. For
these, DDT emulsion used as a spray, toxaphene and DDT as 5
percent dusts and toxaphene ,bait are recommended. From
silking to harvest a 5 percent DDT dust applied at three-day
intervals for four to six applications gives commercial control.
Either ground or air dusting equipment may be used. None of
the above materials affects pollination.
A corn variety that will silk within a two-day period and a
good growing season are two very important factors that de-
termine the success or failure of an earworm control program.
1. Andersen, E. M., et al. Commercial Vegetable Varieties for Florida.
Fla. Agr. Expt. Sta. Bul. 405. 1944.
2. Barber G. W. Mineral-oil treatment of sweet corn for earworm con-
trol. USDA Cir. 657. 1942.
3. Barber, G. W. Styrene dibromide as a substitute for pyrethrum in
oil for corn earworm control. Jour. Econ. Ent. 36:33C-2. 1943.
4. Barber, G. W., and J. Wilcox Styrene dibromide: a substitute for
pyrethrum in insecticidal oil used for control of earworms in sweet
corn. USDA Bur. Ent. & P. Q. E-619. 1944.
5. Barber, George W. Mineral oils, alone or combined with insecticides,
for control of earworms in sweet corn. USDA Tech. Bul. 880. 1944.
6. Carruth, L. A. The corn earworm and its control. New York Agr.
Expt. Sta. (Geneva) Cir. 190. 1940.
7. Davidson, Ralph H. The relative effectiveness of some corn earworm
control measures in sweetcorn. Jour. Econ. Ent. 36:938. 1943.
8. Emmert, E. M., and W. A. Price Control of the corn earworm by
clipping. Ky. Agr. Expt. Sta. Bul. 436. 1942.
38 Florida Agricultural Stations
9. Holloway, T. E., W. E. Haley, U. O. Loftin, and Carl Heinrich. The
sugarcane moth borer in the United States. USDA Tech. Bul. 41. 1928.
10. Metcalf, C. L., and W. P. Flint. Destructive and Useful Insects. 2d
Ed. pp. 368-371. McGraw-Hill. 1939.
11. Pepper, B. B., and G. W. Barber. Dichloroethyl ether in mineral oil
for corn earworm control in sweet corn. Jour. Econ. Ent. 33:584-585.
12. Pepper, Bailey B. The corn earworm and its control on sweet corn.
N. J. Agr. Expt. Sta. Cir. 413. 1941.
13. Watson, J. R., and A. N. Tissot. Insects and other pests of Florida
vegetables. Fla. Agr. Expt. Sta. Bul. 370. 1942.
14. Wilcox, J. Practical field tests of oils and oils containing other in-
secticides for the control of earworm in Southern California Jour.
Econ. Ent. 36:554-557. 1943.
15. Russell, J. C. DDT, a new insecticide for vegetables. Proc. Fla. State
Hort. Soc. pp. 208-210. 1944.