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A tiny insect called the black grass bug is destroying valuable range grasses across the state, says a Utah State University entomologist.

"This is one of the worst infestations I've seen in recent years," said Austin Haws.Damage caused by the bug, coupled with below-normal precipitation levels, could spell big trouble for Utah's range livestock producers, he said. Rangelands provide a large share of feed for Utah's cattle industry, which makes up nearly one-third of the state's agriculture.

Haws and Ted Evans, a USU Extension entomologist, surveyed the black grass bugs May 2-4 from Kanab in the south to Cache Valley in the north.

They reported huge infestations of the bugs on crested and intermediate wheat grasses statewide, except around the Delta area, where populations were lower.

"The bug can be found anywhere there is grazing grass in the state below the 7,000-foot level," Haws said. He estimated damage as high 95 percent on grasses where the bug was found.

Jay Karren, USU Extension entomologist, said livestock producers and others who manage Utah rangelands need to act quickly. The best control method, Karren said, is 8 ounces of Malathion ultra-low-volume per acre, applied from the air.

He said getting cattle to graze on infested lands also helps control the bugs because the cattle will eat many of the eggs. Fall burning also helps.

"Females are preparing to lay eggs now," Karren said, "so if something is not done there could be a bigger problem next year."

As the weather warms in the next few weeks, infestations are likely to appear above the 7,000-foot elevation.

In Haws and Evans' survey, they collected 400 to 500 bugs for each sweep of the net. That compares with Haws' survey in 1986, another year of heavy black grass bug infestations, when he averaged around 330 bugs per net sweep.

Karren said the insect (Labops hesperius) has sucking, not chewing mouth parts. It destroys grasses by sucking out the sap, removing the grasses chlorophyl and nutrients.

As the bug does not present a threat to crops, be said.

Ranchers who need help identifying the black grass bug and developing an effective spraying plan should call the local USU Extension county agent.