xt718911pz81 https://exploreuk.uky.edu/dips/xt718911pz81/data/mets.xml   Kentucky Agricultural Experiment Station. 1952 journals 001 English Lexington : Agricultural Experiment Station, University of Kentucky Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Progress report (Kentucky Agricultural Experiment Station) n.1 text Progress report (Kentucky Agricultural Experiment Station) n.1 1952 2014 true xt718911pz81 section xt718911pz81 CONTROL OF THE CORN EARWORM l
ON
SWEET CORN
IN I
KENTUCKY
Jn G. Rodriguez and W. A. Price
Progress Report No. 1
Department of Entomology and Botany
— Agricultural Experinoent Station
University of Kentucky
Lexington
February, 1952

 CONTROL OF THE CORN EARWORM
ON
SWEET CORN IN KENTUCKY
J. G. Rodriguez and W. A. Price
Department of Entomology and Botany
Progress Report 1
The corn earworm, Heliothis armigera Hbn. , is easily the
most destructive insect  sweet corn, and heavy infesta-
tions of this pest have occurred in Kentucky through the years.
Garrnan and Jewett in 1914 described fields which were 100 per-
cent infested,The situation apparently remains unchanged for it
is quite common to find untreated sweet corn fields with virtual-
ly every ear infested.
lnfestations are not limited to corn; much damage is done
yearly to tomatoes in Kentucky by this insect. Corn is the pre-
ferred host, however, and losses are particularly heavy from J
the infestations of this insect when plantings of market sweet _
corn are made in succession during the season. ln this situation,
the earworm populations have the opportunity of building up in
successive generations. I
Control measures have to be aimed at the hatching larvae in
the corn silk; the eggs are deposited on the silks and the hatching
worms immediately seek to tunnel they way down the silk channel 1
to the ear to the kernels. Emmert and Price (1942) found that
clipping of corn silks, after the silks had begun to dry, provided
good control of the earworm; this was a more effective and more
economical method of control than a pyrethrum-oil treatment
which was applied by hand to the individual earn
With the advent of the chlorinated hydrocarbons, in the past
several years, much work has been done by various investigators
in the control of the corn earworm on sweet corn. Kelsheirner ”
et al. (1950) tested DDT, methoxychlor, parathion, chlordane,
and toxaphene on corn earworm and found that DDT gave the best
and most consistent control. Blanchard et al, (1950) also found
DDT the most satisfactory of the materials used. This report
and other studies by different investigators agree further that
sprays of DDT and mineral oil are considerably more effective
than dusts.

 G3, U
Because the population level of the corn earworrn is probably
the most important single factor in corn earworm control and be~
cause this population level is likely to be different in different
parts of the country, it is essential that the control problem be
studied in each area. Other variable factors which have an in-
fluence on the control program are: corn varieties, cultural `
practices, and, of course, the climate or weather.
Recent Work in Kentucky
This progress report is presented in order to give sweet corn
growers in the state an indication of what to expect in the way of °
infestation levels and the control that can be obtained under various
conditions., The work thus far (1950-51) has been conducted in
large field plots with the cooperation of market sweet corn growers
in the Louisville area. 1
Methods and Materials. Dusts were applied with a conventional
power dusgr using three fixed nozzles per row. Sprays were
applied with a self-propelled high clearance sprayer equippedwith
` a boom and extension drops, allowing three fixed nozzles per row,
and applying about 25 gallons per acre at 100 pounds pressure.
DDT, 25% xylene based emulsion concentrate, was used in all the
sprays. This was used at 3 quarts (1 1/2 pounds) to the acre.
White mineral oil (70-80 second Saybolt viscosity) was used at l 1/,4
and 2 1/Z gallons (5 and 10 perrcent) per acre. The emulsifiable
DDT concentrate plus the mineral oil were diluted to 25 gallbns, the
amount used peracre. Agitation was provided by a strongcoverflow
stream into the tank.
The plots were eight or more rows wide and usually several
hundred feet long; treatment was under light and heavy infesta-
tions and at different times in relation to silking as well as varying num--
bers of applications. On treatments calling for several appli- _
cations, they were made at 3 or 4-day intervals depending on the
_ weather and the development of silking. (Unfortunately the work
could not be made extensive enough to give data on all combina-
tions under the various infestations. )
Results. The following tables summarize the results obtained in
., the work in the Louisville area during 1950-51:
1‘The assistance of Mr. William A. Schneiter, Mr. William
Fagenbush, and Mr. H. C. Brown is gratefully acknowled ed.

 -4- .
Table 1. Summary — Corn Earworm Control withDusts
Applzlcatznons $0 S1l1<1ng Worm'- ree
Materials Pounds and at First Ears
per acre Interval Application per 100 ·
Test 1. (Carmelcross)
1. Parathion, 1% 40 3 at 3 days 10 30
Z. DDT, 5% 40 3 at 3 days 10 50
3. Untreated —~ -~» -~— 41
Test 2.. (Carmelcross`) 1
1. DDT, 5% 40 Z at 3 days 20 62
Z. Untreated -·= ·~- »»  10 .
Test 3. (Golden Cross Bantam)
1. DDT, 10% 20 Z at 3 days Z0 89
2. Untreated -- »-·— ~— 45

 ..5.2
Table Z. Summary —— Corn Earworm Control withDDT Sprays
 
Gauomts per acre} Applications % Sillcing Wofmlfyee
________,______a_______ and at First Ears
. 3
DDTZ 011 l:nte:¤:·val Application per IOO
 
Test L {Golden. Cross Bantam)
1 3/44
· l ~~=- 3 at 3 days 10 33 ·
2. 3/4 1 1/4 4 at 3 days 10 90
3., Untreated ——-·—— —= 6
Test Z. (Golden Cross Bantam)
1. 3/4 2 1/2 1 90 89
2. 3/4 21/2. 2 at 3 days 20 98
3. 3/4 1 1/4 3 at 3-4 days 10 97
4. Untreated ·=-— —-- 45
Test 3. (Stowells Evergreen)
I. 3/4 l I/4 2 at 3 days Z0 96
2. 3/4 1 1/4 1 20 76
3. Untreated ·--·— ·»— 45
1 Materials diluted to 25 gallons with water and applied at this
1 rate per acre.
2 DDT, 25% emulsion concentxaatep xylene base, used in all sprays;
3/4 gallons equal 1 1,/2 pounds actual DDT.
. 3 Oil; white 1minera1,, of 70-80 second Saybolt viscosity.
Y 4 "C011tim1ed European Comm Boxer spray" -· No mineral. oil.,
There was only it0.sigr1.;T.iican.t iznjuiry caused by the use of any of
the DDT »~ m;i.1i1e;<*al oil treatments. There was evidence that the
I Stowells Evetzlgxeen variety was rnore susceptible to i¤.n.ju1·y than
Golden Cross Baxitaml
Samples of corn treated with DDT dust, DDT em1.1.Z|.s11or1 concerl.---
ticate, and the m1nera.¥. oxxl m1C.?»¢tu.ire =» were frozen and later sub~
m1ttted to a panel oi judges of the Home Ec;o1.=omir.is Departrnent.

 -6- ·
The samples were tasted as corn—on-the-cob and_cr€am _ ~
style; the taste panel found no difference in the treated and un-
treated samples.
Conclusions. 1. Spray mixtures of DDTand mineral oil were
superior to any other material tested in corn earworm control,
and gave satisfactory control under high infestation conditions,
2. DDT, without mineral oil, used as a "con-
tinued European corn borer spray" was totally unsatisfactory as
a corn earworm control measure under a high infestation con-
dition.
3. Adequate control with dusts can be obtained
only when the infestation is very low.
4. There is no accurate way to determine a pop-
ulation level of corn earworm ahead of time.,
i 5. If the silking period is prolonged, the control
becomes more difficultt Four applications at 3,-day intervals `
will usually cover prolonged per iods. C A
6. While only insignificant injury to husks or leaves l
occurred, it is felt that a mechanical agitator would practically
eliminate the possibilities of "burning" and inadequate control
due to separation of the DDT and oil, ·
7r No injurious affects to pollination were observed., V
8. DDT and mineral. oil treatments did not cause
off—flavor in sweet corn.
CONTROL MEASURES
On the basis of present knowledge, the following suggestions
can be made:
Commercial Plantings, V
Use. DDT, xylene base, 2.5% emulsion concentrate, Squarts
white mineral oil, (70-80 second Saybolt viscosity.); I 1/4ga11Ons.
Dilute to Z5 gallons with water

 .47..
Method of Application: Apply Z5 gallons per acre. Direct 2
to 4 noz.zles—at ear zone using 100 (or more) pounds pressure.
Mechanical agitation is almost a necessity.,
Timing and number of applications; Apply four applications
starting at IO per cent silk and continuinggrt; 3-day intervals. This
should give satisfactory control under high infestation conditions.
lf only two or three applications are to be made start at 20 per
cent silk and space the other applications to cover the silking
period. Doubling the mineral oil to Z l/2 gallons will aid in con—— A
trol if only two mr three sprays can be made.
Smaller Plantingst (Individual Ear Treatment).
l. Knapsack Sprayers. Use the same materials and methods
as described above. Constant agitation and maintenance of pres-—
sure as high as possible are required. To make one gallon of
mixture iuse about 4 Il. oz. of the DDTandi 6 l/2 fl. oz. of the oil.
Only a small amount of the mixture (1. 5_ cc) is needed per indi-
diviéual ear. ‘
2. Injection. Use a DDT   and mineral oil (99%) mixture
and apply a measured dose per individual ear (not more than 1
cc)*when first wilting appears on the silk. lf application is made
witlra medicine dropper, 1 cc equals one compression of the
dropper.
3. Clipping the Silks. Clip the silks and shucks to the tip
of the cob 4 to 6 days after the first silks brown. Destroy cut ·
portions. V
Literature Cited
l. Blanchard, R. A.- , W. A. Douglas, G. P. Wene, and O. B.
Wooten. 1950. DDT sprays for control of the corn earworrn
and the budworm in sweet corn. U. S. D. A. , Agric. Res.
Adm.} B. E. & P. Q. Ee'780 Rev.

 -3-
Z. Emmert. E.lVI. and W. A. Price. 1942.. The control of
of the corn earworm by clipping. Ky. Agric. Expt. Sta.
13111.436. '
3. Garrnan, H. and H. H. Jewett. 1914. The life-history and »
habits of the corn earworm (Chloridea obsoleta). Ky.
Agric. Expt. Sta. Bul.-l87.
4. Kelsheimer, E.G., N. C. Hayslip and J.   Wilson.
1950. Control of budworms., eaxmorms and other insects
attacking sweet corn and green corn in Florida. Fla.
Agric, Expt. Sta. Bul.466.
V/