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Wheat head armyworm, midge have low impact

Two insect pests are not expected to have much impact in the Pacific Northwest this year, according to WSU Extension specialist Diana Roberts.
Matthew Weaver

Capital Press

Published on July 11, 2014 4:34PM

Wheat farmers are unlikely to see much impact from two insect pests beginning to show up in the region, a Washington State University Extension specialist says.

Washington State University Regional Extension Specialist Diana Roberts found a few larvae that could be the wheat head armyworm at WSU’s Wilke Farm in Davenport, Wash., and few adult moths in pheromone traps.

“It’s a really intermittent pest,” she said. “Even in other areas of the country where it’s found, it will be there for a year or so, and then it doesn’t show up for several years. Which makes it a hard insect to study — not enough is known about it.”

Several years ago, researchers collected several “true” wheat head army worms, but also a similar native species, the false wheat head army worm, and several other moth species.

To identify the insects, researchers must find the larvae feeding in the field and raise them to an adult moth. Roberts collected larvae last year, which will be identified by a USDA entomologist in Wapato, Wash., this summer.

Identification will help determine the pest’s status. That allows Roberts to provide more information to farmers.

But identification could open up more questions.

“If it’s native, why is it just now becoming a pest?” Roberts said. She wonders what factors are going on to allow the insect to become troublesome.

Beyond a few isolated cases, farmers are also unlikely to experience a problem with wheat midge.

Both insects are relatively new pests for cereal grains in the Pacific Northwest. Roberts has been studying the range and impact of the insects for several years, with funding from the Washington Grain Commission.

Neither has achieved widespread pest status, Roberts said.

Roberts advises farmers to walk their fields and report sightings. She cautions against spraying insecticides and damaging beneficial insects. Often, insect damage is worse on the edge of the field, she said.

Pheromone traps give an indication of the insect levels. There have been very few midge males turning up in traps, Roberts said, but even if there’s more males, that doesn’t mean there are many females. She recommends farmers go out at dusk to count females laying their eggs on spring wheat or barley plants.

The pheromone traps are capable of drawing in males from a large area and not necessarily indicative of the populations in a field, she said.

Wheat and barley plants are susceptible to wheat midge damage only from head emergence to when flowering is complete. Planting early or late can help avoid the pest, she said.

Roberts and crop consultants continue to monitor traps.




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