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April 18, 2002

Report from Lee Townsend, Extension Entomologist
Department of Entomology
University of Kentucky College of Agriculture

Eastern tent caterpillar egg hatch is virtually complete in Central Kentucky and many larvae are 1/2 to 3/4 inch long.  These are in the “small” size range so application of a foliar insecticide can be made during next 7 to 10 days (April 19 - 26) with optimum results.

Bud break and leaf expansion of individual wild cherry trees has been variable this spring.  Waiting for leaf expansion on trees that are lagging behind is very important.  Bt-based (Bacillus thuringiensis) insecticides must be ingested by the caterpillars in order to be effective.  Therefore, the more green leaf tissue present to catch spray residue, the better.  The target site for application is foliage around the developing tents.  Sprays onto tent silk or caterpillars will not provide control.

Caterpillars stop feeding soon after eating foliage treated with a Bt insecticide but will not die for 3 to 5 days.  During this time they will look and behave as if they are healthy.  Wait about 5 days before examining infested trees to assess control.

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