Eastern tent caterpillar egg hatch was reported March 23 in Scott County.
Lee Townsend, PhD, University of Kentucky College of Agriculture, Food and Environment extension entomologist, said the tiny larvae will continue to emerge over the next two weeks from eggs laid last summer on flowering wild cherry, cherry, apple, and related trees.
The eastern tent caterpillar spends the winter as tiny, fully developed insects in distinctive egg masses that encircle twigs of wild cherry and related trees. It is one of the first insects to become active in the spring and is well-adapted to survive Kentucky’s erratic winter and early spring weather.
“This is a hardy insect, so it is unlikely that our winter temperatures caused much mortality,” Townsend said. “Studies have shown that caterpillars in the egg can withstand temperatures down to 31 below zero Fahrenheit.”
Populations of eastern tent caterpillars have been climbing over the past few years. This trend is likely to continue, he said, producing locally high numbers in some areas. The rise in numbers is normal and mirrors the cyclical aspects of insect populations in general. Eastern tent caterpillar cycles are roughly 10 years in length, said Townsend. After two or three high years, the numbers usually drop again due to diseases or natural enemies.
When mature, the large, hairy caterpillars wander from their developmental sites along fencelines. Consumption of large numbers of caterpillars by pregnant mares precipitated staggering foal losses in the mare reproductive loss syndrome (MRLS) outbreak that peaked in 2001. MRLS can cause late-term foal losses, early- and late-term fetal losses and weak foals. Studies by UK researchers revealed that horses will inadvertently eat the caterpillars, and the caterpillar hairs embed into the lining of the alimentary tract (which includes the pharynx, esophagus, stomach, small intestine, and colon). 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.