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Project Leader: Richard W. Straub, Cornell’s Hudson
Valley Lab., Highland NY
Cooperator(s): John Gill, Gill Corn Farms, Inc., Hurley,
NY
Teresa Rusinek, Ulster County CCE, Kingston, NY
Type of grant: Monitoring, forecasting, and economic
thresholds
Project location: Throughout the Northeast
Abstract: Corn earworm (CEW) is an annual pest of sweet
corn in most of the Northeastern US and requires multiple applications of insecticides
to manage below a threshold level. It is commonly believed that CEW do not oviposit
(i.e., lay eggs) on sweet corn silks after they have dried. If true, insecticide
treatments could logically cease at some predetermined time interval after pollination,
because silks commence drying within hours of pollination. Problematic however,
is that neither conventional wisdom, nor the historical literature, precisely
defines the point at which silks are sufficiently dry to become unattractive
for oviposition. We hypothesized that CEW cease to oviposit on silks that are
50% dried. Field experiments, utilizing silk dryness treatments ranging from
0% to 75% and methods to prevent oviposition before the silk dryness targets
were attained, were performed during 2001 by which to better define a silk stage
treatment threshold for CEW. Under high infestation pressure from CEW, results
did not confirm our hypothesis, for 50% and 75% silk dryness treatments yielded
58.4% and 44.3% infestation of ears, respectively. Visual estimations of silk
dryness however, correspond well to simultaneous measurements of % loss of silk
wt. Possible reasons for the erroneous hypothesis are discussed.
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