A new cut worm pest in winter wheat

Farm and Ranch February 15, 2010 A moth called the greater yellow underwing has been in the Pacific Northwest states for several years, but in 2009 crop damage in winter wheat was reported from the feeding larvae stage of the insect.

Bechinski: “Because it has a broad host range we saw some fields last spring, we are talking about February, March, April in north Idaho where there were essentially 50 acre holes eaten out of these fields during the winter time.”

That is University of Idaho entomologist Ed Bechinski who says the damage appeared as if plants had been clipped with a scissors.

Bechinski: “These are the caterpillars that hatch from eggs in September and they fed October, November, December, January. They are going to feed right through the later part of April when their feeding is going to end.”

Bechinski believes the greater yellow underwing is probably present in every county in Idaho, Washington and Oregon and now is a good time to look for them in winter wheat fields.

Bechinski: “You are not going to see it during the day because it is hiding under clods and residue. So you have to brush that aside next to the areas where you have this damage. The alternative would be to go out later in the spring with a flashlight at night and you can actually see the caterpillars crawling up on the plant.”

Mature caterpillars are 1.5 to 2 inches long and will stop feeding so they won’t cause more damage. It’s the smaller ones that are of concern. Economic thresholds are not available but several commercial insecticides are effective on the pest. The larvae are olive brown with a series of broken black dashes on each side of the body segments. http://www.cals.uidaho.edu/edcomm/pdf/CIS/CIS1172.pdf

I’m Bob Hoff and that’s the Northwest Farm and Ranch Report on the Northwest Ag Information Network.

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