By TIM THORNBERRY
Kentucky Correspondent

LEXINGTON, Ky. — Seven years ago that Kentucky was embroiled in a terrifying mystery surrounding its lucrative horse industry. Countless foals were dying for no apparent reason.

What became known as mare reproductive loss syndrome (MRLS) took nearly 30 percent of the thoroughbred foal crop in 2001-02, and months for researchers to find answers for the mysterious deaths.

Total monetary losses were estimated anywhere from $300 million to $500 million.

After months of speculation, the culprit was finally determined to be the Eastern Tent Caterpillar.

This year, experts are warning that population levels could be as high as those in 2001.

Mares that inadvertently digested the caterpillars contracted the disease, which can cause small hairs on the caterpillar’s exoskeleton to partially penetrate the intestine, potentially resulting in abortion, according to research at the University of Kentucky (UK).

“The eastern tent caterpillar populations are dramatically up this year – the highest I’ve seen since the MRLS crisis. The larvae are full size, many trees are totally defoliated and I’ve seen very large numbers of caterpillars moving along fence rails and wandering out many meters into pastures adjacent to the cherry trees we are using to conduct eastern tent caterpillar trials,” said Dan Potter, UK College of Agriculture professor of entomology.

“Maturation and wandering of eastern tent caterpillars is occurring a bit late this year due to the cooler spring.”

A report from the Department of Entomology at Auburn University states that the caterpillar can be found throughout the eastern U.S., west to the Rocky Mountains and north into southern Canada, and can be traced back to Colonial times.

The report also noted the caterpillar “is a foliage feeder and, as the name implies, a web- or tent-maker. Cherry, apple and other trees of the rose family (Rosaceae) are the preferred hosts, but larvae have been reported to feed on a variety of hardwoods, including ash, birch, blackgum, oak, sweetgum, maple and poplar.

“The grayish-white silken tents seen in forks of trunk and limb or at junctures of large branches in the crowns of preferred hosts are constructed by the larvae.”

Barry Robinette, manager at Glenwood Farm in Woodford County and president of the Thoroughbred Farm Managers Club, said those losses seven years ago were frustrating for the industry but helped in preparation for what is happening now.

“It was pretty strange at first. It was around Derby time, a time we should have been enjoying, but instead we had all these problems,” he said. “At first we thought it might just be bad luck for us. The farm I worked on at the time only lost two foals.

“But people became frustrated as it continued. We were just grasping at straws until we began to get more information about the caterpillars. They were just everywhere that year.”

Robinette added that he never would have imagined something like that causing the deaths, and that it felt like something out of a science fiction book. He also said since then, he and other farm managers have taken precautions every year to make sure it doesn’t happen again.

“We have pretty much stayed on top of this since then,” he said. “We inject our trees every year with a pesticide to get rid of the caterpillars, and removed all the bad trees.

“We’re always on the lookout every year at this time when the leaves start coming out. It has been expensive, but it’s worth it.”
UK entomologists are recommending removing host trees or keeping pregnant mares out of pastures bordered by cherry trees or other hosts for the next several weeks unless they have otherwise been aggressive in managing the caterpillars.

Research has shown the caterpillars go through population explosions, of sorts, followed by a decline for several years. In the United States, the timeframe between those extremes generally runs about 10 years, prompting warnings to farm managers to be vigilant until 2009.

The horse industry in the state leads all other agricultural commodities, representing more than $1 billion dollars to the economy.