University of Wyoming Extension News

Sheep producers should benefit from new UW research

Wool growers wondering how to control perhaps the most serious insect pest that can affect their animals and ultimately their pocketbooks will welcome research by a University of Wyoming College of Agriculture team working in collaboration with others.

Their studies found that the commercially available PYthon ear tag effectively controls the sheep ked, a blood-feeding insect that can ruin pelts and cause a reduction in weight gains, fleece production and fleece quality.

The joint research project by the UW College of Agriculture, Montana State University (MSU) and U.S. Department of Agriculture (USDA) also determined the insecticide Permectrin WS, when sprayed on sheep, effectively controls the ked.

Permectrin WS is not currently sold in the United States, but cooperation between the sheep industry, manufacturer (Houston-based KMG Chemicals Inc.) and others could make it available to producers, according to the researchers.

Conducting the studies were project leader Jack Lloyd, professor emeritus in entomology in the College of Agriculture’s Department of Renewable Resources; Bob Stobart, associate professor in the College of Agriculture’s Department of Animal Science who specializes in sheep and wool; Will Reeves, an entomologist with the USDA’s Arthropod-Borne Animal Diseases Research Laboratory in Laramie; and Greg Johnson, Rodney Kott and Hayes Goosey with MSU’s Department of Animal and Range Sciences in Bozeman, Mont.

Lloyd will present the team’s findings at the American Sheep Industry Association’s annual convention Jan. 21-24 in San Diego.

Of particular concern to sheep producers is the damage caused by keds to the pelts of market lambs, according to a paper by the research team.

Feeding by the sheep ked is responsible for a condition in the pelt known as “cockle.” The cockle is a nodule or deposition of dense, fibrous material in the hide resulting from an allergic reaction to the salivary secretions of the ked. The blemish cannot be softened, and these nodules will not accept a dye evenly.

The result is an inferior leather product that is unacceptable to the garment industry and results in significant loss of income to producers, according to the paper.

“Both the PYthon ear tag and Permectrin WS spray work well in the control of keds,” Lloyd said. “They will be effective replacements for Ectrin WDL.”

In 1983, research by Lloyd, in cooperation with Fermenta Animal Health, demonstrated that the insecticide Ectrin WDL eliminated the sheep ked from test flocks in Wyoming.

“Unfortunately,” Lloyd said, “Ectrin WDL is no longer available to U.S. producers because the active ingredient, fenvalerate, is no longer licensed in the United States.”

Stobart added, “It’s my understanding the company believed it wasn’t economical to go through the relicensing process. They decided the cost-benefit ratio wasn’t there.”

Other commercially available insecticide formulations have not been as effective as Ectrin WDL, Lloyd said, and many flocks have once again become heavily infested.

Lloyd said he and other members of the research team are confident use of Permectrin WS, if it becomes available, and the PYthon ear tag will allow producers to control keds easily, safely and cost effectively.

Stobart said PYthon ear tags are now commonly used to control flies and lice in livestock as well as the biting midge that carries the virus that causes bluetongue in sheep. A bluetongue outbreak in Wyoming’s Big Horn Basin in 2007 killed more than 300 sheep.

PYthon tags cost about $1.50 to $2.25 each, depending on the number purchased.

“If Permectrin WS becomes available, the cost should be considerably less than the cost of ear tags,” Stobart said.



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