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WSU issues wheat midge alert

Published on July 13, 2011 3:01AM

Last changed on August 10, 2011 2:59PM

Washington State University scientists report that a spring wheat pest has been captured in low numbers in pheromone traps in three counties.

The wheat midge has been captured in Spokane County's Peone Prairie area, Lincoln County and Garfield County.

WSU Extension Agronomist Diana Roberts said in a press release that farmers should not apply insecticide unless they know they have an infestation. Close examinations of wheat fields in the area have not revealed populations that will likely cause economic damage, she said.

Spraying crops can kill beneficial insects, she said.

According to the release, spring wheat crops are most susceptible to egg-laying infestation by the midge from the time the wheat heads until anthers hang out of the florets. After that time, the midge causes little damage. Winter wheat and barley crops are seldom affected.

The midge needs warm, calm weather and moisture for successful egg laying.

Roberts is in contact with researchers in Canada who have biological controls for the wheat midge.

"While the midge populations are still at low levels, we will take the opportunity to bring in the biocontrols," she said.

In March, University of Idaho entomology professor Ed Bechinski told the Capital Press the wheat midge was reliably confined to Boundary County in Northern Idaho for 20 years, but had begun to move outside that region in recent years.

The adult midge is a fragile insect with a body type similar to a mosquito, but about half the size. It has an orange body, conspicuous black eyes, three pairs of long legs and one pair of wings. The female lays eggs on the awns and heads of wheat plants. The eggs hatch into larvae that crawl inside the floret and feed on the very young, developing grain and cause yield loss and shrunken kernels. The larvae are about the same size, shape and color as the anthers of the wheat floret.

"Take care with identification," Roberts said. "There is a lookalike fly that has an orange, but fat body and it rests head downwards in the wheat."

Information: Contact Roberts at 509-477-2167 or robertsd@wsu.edu .

-- Matthew Weaver


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