03/26/2015 1:50PM

Eastern tent caterpillar egg hatch begins in central Kentucky

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A hatching of Eastern tent caterpillars, which have been associated with Mare Reproductive Loss Syndrome (MRLS), was reported March 23 in Scott County, Kentucky, north of the heart of the Thoroughbred breeding industry in Lexington.

Tent caterpillars are one of the first insects to become active in the spring, hatching from eggs laid last summer on wild cherry, cherry, apple, and related trees. Populations of the caterpillars have been climbing over the past few years, a trend likely to continue in the near future.

“This is a hardy insect, so it is unlikely that our winter temperatures caused much mortality,” Lee Townsend, University of Kentucky College of Agriculture, Food and Environment extension entomologist, said. “Studies have shown that caterpillars in the egg can withstand temperatures down to 31 below zero Fahrenheit.”

The Eastern tent caterpillar played a key role in the outbreak of MRLS in Kentucky from 1999 to 2001. According to a University of Kentucky survey of 159 Thoroughbred farms taken during the outbreak, 21 percent of the 3,294 pregnant mares on those farms had experienced early fetal loss.

MRLS can be contracted when mares inadvertently eat caterpillars and the insect’s hairs embed the lining of the gastrointestinal tract, which can cause bacteria to gain access to and reproduce in places with low immunity protection, including the fetus and placenta.

Experts suggest that owners with pregnant mares should begin to monitor fence lines in the coming weeks for small tents produced by developing caterpillars. If practical, farms should move pregnant mares from areas where cherry and other trees are located to minimize chances of exposure. The potential for exposure is highest when mature caterpillars leave trees and wander to find places to pupate and transform to the moth stage. To get rid of active caterpillars, Townsend recommends pruning them out and destroying nests as they are seen.