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May 2, 2003

Barrier Treatment for Tent Caterpillars Crawling Through Grass

Dan Potter, Professor
Department of Entomology
University of Kentucky College of Agriculture

Large tent caterpillars are beginning to wander from infested trees in search of pupation sites.

Field tests conducted earlier this week by UK entomologists as part of a Grayson-Jockey Club-funded research project indicate that dry residues of a 0.5% tank mix of Astro insecticide will quickly kill large tent caterpillars crawling over or through treated pasture grass. Mortality of caterpillars was 100%. The residues were 1-day old when challenged.

How long such a barrier effect will last will not be known until further trials next week, but it likely will remain effective at least several days, and possibly a week or more. Rainfall the night before the test (after spray residues had dried) did not reduce the effectiveness.

Astro (FMC Corportation) is a pyrethroid insecticide containing 36.8% permethrin. It is labeled for use as a perimeter treatment, including on grass outside of fence lines. The rate used was 1.6 fluid ounces (50 ml) of product per gallon or water, sprayed as a band about 6 feet wide. Farms needing to stop tent caterpillars from crawling into pastures from adjacent untreated areas may want to consider this tactic. Alternatively, Astro can be applied to lower tree trunks or to the ground around the base of trees.

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