05/08/2014 3:38PM

Breeders advised as to rising tent caterpillar population

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The University of Kentucky College of Agriculture, Food and Environment noted in its May 8 Ag News report that a sizeable population of eastern tent caterpillars are mature, have dispersed from trees, and are on the move.

The report advised farm managers to keep pregnant mares away from areas where the caterpillars have been spotted to avoid foaling complications.

The eastern tent caterpillar played a key role in the outbreak of Mare Reproductive Loss Syndrome 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 cause late-term foal losses, early- and late-term fetal losses and weak foals. It can be contracted when mares inadvertently eat the caterpillars and the caterpillar’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.

Lee Townsend, the University of Kentucky’s College of Agriculture, Food, and Environment’s extension entomologist, said the population of eastern tent caterpillars is up in 2014.

“Mature eastern tent caterpillars leave trees in search of protected pupation sites, where they will spin cocoons and transform into adults,” Townsend said to UK Ag News. “This dispersal is a normal part of their life cycle,”

“These wandering caterpillars may move several hundred feet from the trees where they developed,” he continued. “The direction of travel tends to be random and directly related to air and ground temperatures. Movement will be slower when temperatures are cool and faster when they are warm. The caterpillars wander for a period of time until internal hormones signal that it is time to stop and pupate.”

Townsend said that wandering caterpillars are drawn to dark, vertical objects like trees and fence posts, and encouraged farm owners and managers to check those objects to monitor caterpillar movement. He also said that insecticides are not very effective against large, dispersing caterpillars because they do not often eat. Direct treatment may help control the caterpillars, but Townsend said the effect is usually delayed.