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March 27, 2003

Eastern Tent Caterpillar Status

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

Eastern tent caterpillar (ETC) egg hatch is virtually complete in central Kentucky. The very small caterpillars have been moving to feed on expanding leaves and have begun to build small tents (1" to 4" long) at branch and limb forks. Initial growth of the caterpillars will be slow but over the next two to three weeks caterpillars in limb nests will begin to move to main trunk branch angles and join in a smaller number of larger tents on individual trees. This aggregation behavior can be used to advantage in managing the insect.

Trunk injection with bidrin (Inject-A-Cide B) to control ETC larvae should be very effective if made during the next 7 to 10 days. An on-farm trial in 2002 showed that control by injection was much less effective if ETC larvae were more than 1-1/4 inches long.

Foliar sprays for caterpillar control can be made during this time period, as well. Spray residues of products based on Bacillus thuringiensis (Bt) must be eaten by small caterpillars to be effective; there is no contact effect. Consequently, applications should be made to as much of the canopy as is feasible, especially the foliage around active nests. Direct application to nests will not provide any control. Bt residues on foliage can be broken down by sunlight in 3 to 4 days so it is important to assess control and re-treat if necessary.

Foliar sprays with products such as bifenthrin (Talstar) or carbaryl (Sevin) have both stomach and contact activity so they can be effective when sprayed onto foliage or tents. The residual life of carbaryl is about a week; and of bifenthrin at least that long and probably longer.

Regardless of the treatment used, it is important to re-visit the sites in about 5 days to assess caterpillar activity.

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