November 20, 2002 | By: Haven Miller

When teams from the University of Kentucky begin monitoring pastures in early spring, they’ll be looking for signs of a small insect that’s been linked to the cause of a very large problem.

The insect is the eastern tent caterpillar, a hairy little critter that UK scientists believe is the key to unlocking the mystery of Mare Reproductive Loss Syndrome.

“We’re going to focus on the growth stage of these little caterpillars in early spring and be watching for egg hatch and when they’re established in their tents,” said Jimmy Henning, the agronomist in charge of the monitoring program.  “I think one of the largest services we can provide is aiding horse farm managers in locating the caterpillars before they leave their host trees because after that control becomes harder.”

Central Kentucky had heavy infestations of ETC in both 2001 and 2002, and entomologists believe there’s a strong likelihood caterpillar populations in 2003 will again be significant.

Research trials at UK have produced information about caterpillar behavior that will benefit horse farm managers in implementing control measures.

“Eastern tent caterpillars are most susceptible to control when they’re small and are spending most of their time feeding or resting in or around their clearly visible silken tents,” said Lee Townsend, UK entomologist.  “We need to use this instinctive behavior against them while we can.  Once they begin to move from trees, the task becomes much more difficult.  Then, control measures must be applied over a much larger area and the options and degree of success we can expect becomes much more limited.”

Farm managers also should be aware that although caterpillars are closely associated with cherry trees, they also thrive on other trees as well.

“Last summer their eggs were laid on wild cherry and related trees, but if ETC completely strip the leaves from their ‘home’ tree before completing development next spring, they’ll be forced to find additional food,” Townsend said.  “They can survive on leaves of some other trees such as white oak.  Fortunately they do not do well on hackberry, another common fence line tree.”

 Townsend said remembering the acronym “ERASE” will help producers develop their caterpillar control strategies.

“The E and R stand for exposure reduction, meaning keeping pregnant mares in pastures away from cherry trees and the insects, and the A and S stand for directing control measures toward ‘action sites,’ or the tent-like nests where ETC are concentrated and control will be most effective,” he said.  “The E is for elimination, which really means cleaning up the caterpillars that have left trees and are wandering across the ground.  These caterpillars frequently climb fence posts and other vertical objects.”

In addition to scouting caterpillar activity, the monitoring teams also will take a second year’s look at tall fescue in pastures.

“We know it’s not good for pregnant mares to be exposed to the toxic endophyte in fescue so we want to monitor the pastures for another year to give additional information,” Henning said.


Jimmy Henning, 859-257-3144; Lee Townsend, 859-257-7455