Eastern tent caterpillars, which were responsible for massive foal losses that devastated the Thoroughbred industry in 2001 and 2002, have begun hatching in Central Kentucky.
Egg hatch was reported Monday in Scott County, said Lee Townsend, an entomologist with the University of Kentucky College of Agriculture, Food and Environment.
The larvae will emerge over the next two weeks from eggs laid last summer on flowering wild cherry, cherry, apple and related trees, often in fence lines, he said.
The number of caterpillars is expected to be high again this year, despite the cold winter.
When mature, the large, hairy caterpillars wander, creating the greatest danger. Consumption of large numbers of caterpillars by pregnant mares precipitated staggering foal losses known as the mare reproductive loss syndrome outbreak that peaked in 2001. MRLS can cause late-term foal losses, early- and late-term fetal losses, and weak foals.
UK researchers determined that horses will inadvertently eat the caterpillars, and the caterpillar hairs embed into the lining of the alimentary tract. Once that protective barrier is breached, normal alimentary tract bacteria might gain access to and reproduce in sites with reduced immunity, such as the fetus and placenta.
UK recommends that horse owners and farm managers with pregnant mares should begin to monitor fence lines containing wild cherry trees in about two weeks for small tents produced by developing caterpillars.
If practical, farms should plan to move pregnant mares from areas where those trees are abundant to minimize the chance of exposure to the caterpillars.
To get rid of active caterpillars, Townsend recommends pruning them out and destroying the nests as they are seen, if practical.