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Relationship of Sweet Corn Silking Stage to Oviposition by the Corn Earworm 2002

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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:

It is commonly believed that corn earworm (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 during 2001, utilizing silk dryness treatments ranging from 0% to 75% and methods to prevent oviposition before the silk dryness targets were attained, were utilized to test the hypothesis. The results did not confirm our hypothesis, for 50% and 75% silk dryness treatments yielded 58% and 44% infestation of ears, respectively. Duplicate experiments performed during 2002 and reported here, provided similar results. Under extremely high infestation pressure from CEW, all treatments were nearly 100% infested regardless of the degree of silk dryness when exposed to oviposition. Possible reasons for this unanticipated result are discussed.

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