The earliest hatching eastern tent caterpillars (ETC) have finished feeding and have entered the “wandering” stage of their life cycle. Over the next 10 days to 2 weeks, restless tent caterpillars will crawl from their home trees, eventually finding a sheltered spot to stop and spin a cocoon in which they will pupate.
Wandering larvae (Figure 1) may move several hundred yards, using the sun as a compass to direct their general movement. They tend to move in the morning or afternoon; those abandoning trees in the afternoon tend to move the farthest. ETCs orient themselves to contrasting vertical objects, so they may climb fence posts or structures encountered during their journey.
Dispersing eastern tent caterpillars can cause two main problems:
(1) The greatest potential harm is associated with pregnant mares on pasture. Ingestion of these hairy caterpillars can trigger early and late term foal abortions associated with Mare Reproductive Loss Syndrome (MRLS). Keep pregnant mares away from ETC-infested fencerows until caterpillar movement has subsided.
(2) These hairy caterpillars pose a significant nuisance to landscapes located near concentrations of the caterpillars on wild cherry trees, their favored host.
- The size and hairy covering of the caterpillars tends to limit the effectiveness of insecticides, so chemical control is often unsatisfactory. Direct sprays of landscape insecticides containing a pyrethroid (bifenthrin, cyfluthrin, cyhalothrin, or permethrin) are among the best choices. The results of these applications are slow to appear so they can seem to be completely ineffective.
- When practical, sweep up caterpillars and dump them into a trash bag, and then seal. The Velcro-like hooks on the fleshy abdominal legs causes them to cling to rough surfaces, which often turns removal efforts messy.
By Lee Townsend, Extension Entomologist