The forsythia were blooming at the end of March, and in Kentucky, that means that Eastern tent caterpillars (ETC) were hatching. In 2001 and 2002, those caterpillars crawled across many farms in Central Kentucky and left in their path what was later termed mare reproductive loss syndrome (MRLS), which caused abortions in thousands of Thoroughbred broodmares.

The anticipated 2004 ETC population isn’t expected to come anywhere near the number of the hatched insects in 2001 and 2002, but University of Kentucky (UK) researchers are still working to find the mechanism by which the caterpillars cause abortions and to control the ETC population to limit their exposure to horses.

At an open meeting at Keeneland in Lexington, Ky., on March 30, two UK entomologists shared their recommendations for monitoring and reducing the ETC population. Ken Haynes, PhD, detailed his research with female ETC pheromones, which, in tests, have been effective in luring male caterpillar moths to a specific location. This method could be used to predict the size of an ETC crop, to reduce the crop size by disrupting mating patterns, to trap and kill the male insects, or to disseminate diseases among the ETC population.

Dan Potter, PhD, has found that the pesticide Bidrin, a product that is injected into trees where the insects live, resulted in a 99-100% ETC death rate, whether it was administered slightly before or during the hatching stage (which began March 25 in Central Kentucky). Potter also found a 100% success rate when spraying Talstar on young larvae, but Talstar is more toxic than Dipel, which wasn’t 100% effective in killing young caterpillars. Potter also recommended treating egg masses before they hatch, even as early as December