xt7wpz51hs7x https://exploreuk.uky.edu/dips/xt7wpz51hs7x/data/mets.xml   Kentucky Agricultural Experiment Station. 1955 journals 035 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.35 text Progress report (Kentucky Agricultural Experiment Station) n.35 1955 2014 true xt7wpz51hs7x section xt7wpz51hs7x Progress Report 35
Control of Northern Corn Rootworm Adults on Corn
J. G. Rodriguez
Department of Entomology and Botany ‘
In years past there have been occasional reports of infestations of the
adult of the northern corn rootworm, Diabrotica longicornis, destroying the
silks of corn. In 1946, 1947, and 1948 widespread infestations occurred in the I
bottom land corn fields of western Kentucky. During this period, many growers
sprayed or dusted (mainly dusted) their corn fields with DDT, principally by air-
plane, to kill the beetle. Excellent control of the beetles was reported, but a
survey of some 40 treated and untreated fields in 1947 indicated that much of the
plant sterility observed was due to genetic factors rather than to insect damage.
During August, 1955, heavy infestations of the adults of the northern corn
rootworm appeared in some of the bottom lands of Ballard county. Specifically,
the injury was to the emerging silk and damage varied according to the degree
of silking, in a particular field, when the beetle attacked. In some fields the
silks were totally destroyed as they emerged, making pollination almost impos-
sible. Pollination apparently progressed normally or nearly so where the silks '
had been given a chance to attain 2-3 days' growth before the onslaught of the
infesting beetles hit them. Nearby soybean fields were also attacked, but feeding
preference was definitely directed to the emerging corn silk.
In order to study the influence of the beetles on pollination, plastic mesh
bags were tied to ears in various stages of silk development, and beetles were
either added (about 25) or excluded altogether. Observations made while these
tests were in progress showed that,while held in captivity, the beetles evidently ·
did not feed on the silks, even though they remained active for as long as 3 weeks
while caged in this manner. There was no significant difference betweem treat-
. ments in the yield of corn under the conditions described above.
In a test to study chemical control of the beetles, a field of about 230
acres of Stull 400 W, which was beginning to silk, was treated with DDT and
dieldrin. . A high-clearance sprayer, applying 6 gallons of spray mixture per
acre at 100 pounds per square inch and directing one nozzle to each side of the .
ear, was used. Knockdown was immediate, and these beetles evidently all died.
About one bushel of corn was harvested at random from these plots; a summary
of the results follows:
Material (Emul. Conc.,) Av.Wt Percentage Wt
per ear (lb) Increase over Check
Check, No treatment 0. 416 ——-——--
DDT, 2lb/A 0.590 ——--— 41.8
Dieldrin, O. 3 lb/A 0.590 —-——— 41. 8
Dieldrin, 0. 25 lb/A 0.600 —-—-- 44. 2
These preliminary data indicate that gains may be obtained by such treat-
ment of corn; dieldrin, 0.25 pound per acre would be the cheapest material to
apply. Further work planned includes a comparison of ground and aerial applica-
tion methods and a study of timing of sprays in reference to silking.
300-l-56
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