Get the dirt on tuber moths

07/01/2006 02:00:00 AM

Combine insecticides and cultural practices to help manage this profit-robbing potato pest

By Vicky Boyd
Editor

With three years of field trials under their belts, researchers say they are beginning to gain an understanding of the tuber moth, a tropical pest plaguing Pacific Northwestern potato growers.

Insecticides combined with cultural practices appear to control the moth and its offspring, the tuber worm, but scientists admit they still have several questions, including treatment thresholds, that they hope to answer.

"We are in our infancy in understanding how to control this pest,” says Alan Schreiber, president of the Agricultural Development Group of Eltopia, Wash., and a consultant to the National Potato Council in Washington, D.C..

Tuber moths have been the most serious potato pest in the tropics and subtropics for decades. More recently, they have plagued California potato growers in the Kern County area.

But they had rarely been found in the Pacific Northwest until 2002, when several Hermiston, Ore.-area growers were surprised to find fields with significant tuber worm damage.

Tony Amstad, a Hermiston potato grower who had a couple of circles damaged by tuber worms in 2002, says he learned a lesson. He now deploys pheromone traps near every circle to monitor for the pest, and he treats when traps pick up significant moth numbers.

“The tuber moth is a real issue for us,” Amstad says. “It’s moving farther up the [Columbia River] basin.

An expanding problem
Since it’s original discovery near Hermiston, the moth has expanded its range and now is found as far north as Wilbur, Wash., and as far south as the Klamath River Basin bordering Oregon and California. During summer 2005, University of Idaho researchers and Idaho State Department of Agriculture inspectors also found the moth in about two dozen fields in the southwestern part of the state.

Subsequent surveys by University of Idaho scientists that involved looking at foliage for larval feeding and examining thousands of tubers for damage yielded no tuber worms, says Eric Dotseth, an entomology support scientist with the university’s Aberdeen Research and Extension Center.

What does this pest look like?
The nocturnal, 1/2-inch-long, gray tuber moth causes little potato damage, feeding on nectar. Females prefer to lay eggs on the underside of green foliage. If no leaves are available, or if the leaves are dry, they’ll search for tubers exposed by cracked soil or a lack of soil covering.


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