The forsythia are blooming and in Kentucky, that means that Eastern tent caterpillars (ETC) are 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 ETC population in 2004 isn't expected to come anywhere near the number of the insects that hatched in 2001 and 2002, but researchers at the University of Kentucky are still working with two main objectives; first, to find the mechanism by which the caterpillars cause abortions, and second, as a stopgap measure, controlling the ETC population to limit their exposure to horses.
At an open meeting at Keeneland on Tuesday, two University of Kentucky entomologists shared their best recommendations for monitoring and reducing the ETC population. Dr. Ken Haynes detailed his research with female ETC pheromones, which, in tests, have been effective in luring male caterpillar moths to a 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.
Dr. Dan Potter said he is one of 20 researchers at the university working on MRLS. Potter has done further study on a number of pesticides which have proven successful in killing Eastern tent caterpillars. He found that Bidrin, a product that is injected into trees where the insects live, resulted in a 99-100% 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 was effective, but not 100% effective in killing young caterpillars. Potter also said treating egg masses before they hatch, even as early as December, worked well because the residue remained in place.
Potter encouraged those in attendance to support further research. "If we don't understand the mechanism (used by ETC to cause MRLS), we're going to be spraying forever."
Dr. Karen McDowell, who has done much of the research surrounding ETC and their effects on broodmares, was at the meeting. She said she is not currently working on any MRLS projects because she is writing grants for further funding. In January McDowell was part of a fundraising presentation to farm representatives. She would like to further research her hypothesis that bacteria found normally in the horse's digestive tract are allowed into the bloodstream, where they migrate and attack the fetus, eyes, and heart, thus causing abortions.