Entomologists at the University of Kentucky College of Agriculture have studied several insecticides and treatment strategies to find out how well they work for control of Eastern Tent Caterpillar, the insect associated with Mare Reproductive Loss Syndrome.  The studies involved reduced-risk products, meaning products or application methods which are safer in terms of use near livestock.

Study results indicate effective control when certain products are used in a timely manner consistent with label instructions.

“We found that Talstar sprayed on the leaves of host trees was extremely effective in controlling all sizes of Eastern Tent Caterpillar larvae,” said Daniel Potter, UK professor of entomology.  “We also found that Dipel was effective against small larvae, although it was a little slower in terms of how long it took to do the job. Dipel was less effective, however, against large larvae.”

Potter presented the information to horse owners and managers January 31 at a meeting sponsored by the Grayson-Jockey Club Research Foundation held at Fasig-Tipton sales pavilion.

UK entomologists also studied a control method called “micro injection.” Micro injection refers to insecticide being injected into the base of a tree which contains caterpillars nests.

“The product Inject-A-Cide ‘B’ was very effective when directed against small caterpillars, and excellent control was observed within one week after micro injection treatment,” Potter said.

He said some of the products studied are restricted-use pesticides, meaning applicators must be certified to use them.

Researchers also studied the efficacy of horticultural oils and insecticidal soaps. These products did not prove to be effective.  Potter said tests of winter control of unhatched larvae still inside egg masses are under way, but early results indicate pesticides have difficulty penetrating the tough outer layer of the ETC egg mass, which is similar to plastic “bubble wrap.”

A study in which pastures were sprayed to kill caterpillars crawling across them to find food or a place to spin their cocoon gave poor control.

Central Kentucky had huge populations of ETC in 2001 and 2002.  Potter said there are fewer egg masses in trees this year and that indicates the likelihood of reduced numbers of caterpillars in 2003.  However, farm managers should still be vigilant and take appropriate control measures.

“We still don’t know the precise mechanism by which the presence of Eastern Tent Caterpillars leads to MRLS, so we still need to control the caterpillar and keep mares away from them,” he said.

Potter urged the equine industry to continue to support research to identify the basic mechanism of MRLS so that hopefully in future years the need for chemical control of ETC will be lessened.