By MATTHEW WEAVER

Capital Press

Researchers hope a new combination of chemicals will be approved to help combat the wheat pest wireworms.

Washington State University entomologist Keith Pike and WSU Extension agronomist Aaron Esser provided an update on wireworm control efforts to the Washington Grain Commission meeting in Spokane.

Wireworms are the larvae of click beetles and can damage cereal crops, increasing weed pressure and decreasing yield and profits, primarily in spring wheat.

Pike said the combination of the chemicals thiamethoxam and fipronil would eliminate wireworms for three to four years, including new eggs that hatch. The combination would be more effective than the chemical lindane, considered by farmers to be the most effective control method until it was discontinued in 2006.

A higher rate is used per acre in potatoes, so Pike is hopeful label approval can be sought from the Environmental Protection Agency to register the chemical combination for use in wheat.

Neonicotinoids are a class of insecticides related to nicotine. The chemicals clothianidin, imidacloprid and thiamethoxam are registered as effective and have proved useful on high populations of wireworms, Pike said. But those chemicals need to be applied each year.

"Neonicotinoid seed treatments will reduce wireworm populations, but they will never entirely eliminate the problem," Pike said.

While waiting for label approval, Esser recommends farmers introduce a no-till fallow segment into their crop rotations.

He also suggests identifying and accurately assessing the situation and wireworm populations on site. Some farmers may panic when they find one hot spot and apply chemicals unnecessarily to the entire field, he said.

"Some people are making rash decisions based on 3 percent of their ground," he said.

Tom Zwainz, chair of the board for the grain commission, has had wireworms on farmland in Reardan and Colfax, Wash., for the last four years. He's used high rates of the pesticides Gaucho and Cruiser to keep the wireworms in check, but still has hot spots.

"In higher rainfall areas, it's a big issue," Zwainz said. "It's not just confined to direct seed programs. Conventional farms are having the same definite impact."

Pike plans to retire from WSU in April 2013 after nearly 37 years, but he expects the wireworm control efforts will increase with the continued work of Esser and the rest of the team of researchers.