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March 31, 2004

Eastern Tent Caterpillar Status

Lee Townsend, Dan Potter, and Beth Ann Choate
Department of Entomology
University of Kentucky


Most eastern tent caterpillar (ETC) egg masses should have hatched by now in central Kentucky. Scattered observations point to an overall population level comparable to 2003. Caterpillar numbers should be well below area-wide outbreak levels but there will be some strong local pockets of infestation. Careful inspection of wild cherry and related trees is the way to assess the situation on your farm. Now is the time to begin looking.

ETC larvae are still very small but they are feeding on leaf buds and have started to form tents at branch angles. The tents will become more visible as the caterpillars grow and add to the structure. This will be the key to use and determine treatment sites and timing. At this point, the first full week of April should be the time to assess treatment with continued inspections as needed.

Caterpillar management options are the same as those recommended for 2003. Foliar sprays of Bacillus thuringiensis (Bt) products or the pyrethroid Talstar should be made when the tents are about the size of a baseball.

Bt residues must be eaten by the caterpillars so treatment should be directed at foliage around active tents. Bt products are most effective against caterpillars that are no more than 1 inch long. Residues of these products are broken down by sunlight and remain on the foliage for less than one week. Two applications of Bt products may be needed for adequate control. Mortality results from disruption of the gut lining of the caterpillars so they do not die until several days after ingesting the material.

The pyrethroid Talstar has contact and stomach poison activity and has a residual life of about 1 week after application. As with Bt products, targeted applications should be used, not full tree sprays.

Trunk injections of Bidrin have been used successfully to control ETC larvae. As with foliar sprays, baseball-sized tents are a good clue for timing treatment if injection is warranted.


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