Eastern tent caterpillars, responsible for the deaths of hundreds of Central Kentucky Thoroughbred foals and abortions of thousands more, have begun hatching early, according to University of Kentucky entomologist Lee Townsend.
Townsend said horse owners and farm managers with pregnant mares should begin to monitor fence lines containing wild cherry and other host trees in about 10 days. Developing caterpillars will begin small tents in the trees; once mature, they begin to move, and farms should be plan to move pregnant mares away.
The first caterpillars were spotted Thursday in Scott County, he said.
“This year’s first observed hatch is seven days earlier that 2015, reflecting the warm spring temperatures,” Townsend said in a UK news release. “The hatch is not synchronized; tiny larvae will continue to emerge over the next two weeks from eggs laid last summer on wild cherry, flowering cherry, apple and related trees. This is a hardy insect, so predicted low temperatures in the 30-degree Fahrenheit range late this week should not affect their survival.”
The number of caterpillars has been on the rise in the past four to five years and is expected to rise again this year; the population peaks about every 10 years.
The hairy caterpillars hatch and grow, then begin wandering, often along fence lines, for hundreds of yards. When pregnant mares come into contact with them, the results can be devastating.
In 1999-2001, heavy caterpillar populations caused the outbreak of what has been identified as mare reproductive loss syndrome, which causes late-term foal losses, early- and late-term fetal losses, and weak foals.
UK researchers discovered that horses will inadvertently eat the caterpillars, and the caterpillar hairs embed into the lining of the horse’s alimentary tract. Once that protective barrier is breached, normal alimentary tract bacteria can gain access to and reproduce in sites with reduced immunity, such as the fetus and placenta.