April 2007
Pacific Northwest Taking Proactive Measures to Stop Threat

The recent discovery of potato tuberworms (PTW) and tuber moths has potato growers and industry officials concerned and researchers studying how and why tuber moth, thought to be a subtropical pest, has migrated to northern latitudes where it has not been seen before.

Has it genetically mutated, is it responding to global warming or has it been introduced from somewhere else? These are just some of the hypotheses being explored by researchers in Washington, Oregon and Idaho.

There has been some evidence, mostly anecdotal, that tuber moths have been in the Columbia basin before. But in 2002, they were found in north central Oregon in Hermiston, and since then they have been found in traps from Hermiston, Ore., to the Northern Columbia Basin in Wilbur, Wash. In the summer of 2005, they were documented in southwestern Idaho for the first time.

On Aug. 26, two PTW moths were caught at the University of Idaho’s experimental station at Parma in southwest Idaho. At that time, 36 pheromone traps had been deployed in the fields. Following the discovery of the moths, the Idaho State Department of Agriculture, University of Idaho researchers and industry officials decided to implement a more extensive survey by deploying 461 traps throughout southern Idaho.

Between Aug. 26 when the first moths were trapped and Dec. 2, the traps netted a total of 19 PTW moths in three western Idaho counties: Canyon, Payette and Elmore. No moths were found east of Elmore County.

University of Idaho Extension Entomologist Juan Alvarez, located at the University of Idaho Research and Extension Center in Aberdeen, has been warning growers and processors to be alert to potential infestations. It’s a problem that has loomed on Idaho’s horizon. PTW infestations are believed to have been a recurring problem in the Columbia Basin during the past two decades, but the severe infestation in Hermiston, Ore., in 2002 has been followed by additional infestations in the region since then.

Alvarez considers the PTW to be a real threat.

It’s probably the most important potato pest in the world,” Alvarez said. “It causes two kinds of damage; it infests the fields and infests the plants and causes lower production, but it also infests the tubers in storage places, in the cellar, and if you have ideal conditions in the cellar, you could have insects the whole year; you have overlapping generations and you have insects the whole year.”

According to Alvarez, the Idaho Potato Commission is trying to take a proactive position by setting traps to locate initial infestations.

“We talked about this insect three years ago with the Idaho Potato Commission,” Alvarez said. “This insect hasn’t been in Idaho for almost 50 years. As soon as we see any moth sightings that would suggest an immediate introduction, we propose efforts initiated to isolate, control or prevent them, and early detection is the best means to contain any future spread of this pest.”

Alvarez is very cautious when discussing the source of the PTW moths and chooses his words carefully so as not to offend neighboring states.

“It’s not a good flyer. What happens is that the infested tubers are transported from infested places,” he said.

“This insect has not been found in any larval stage in Idaho and so far we haven’t found any plants with damage and any tubers with damage. What we have found is adults (moths) in the pheromone traps.”

The Idaho Potato Commission’s concerns can be traced to the recent infestations found in the Columbia Basin. Since 2002, tuber moths have been captured in pheromone traps from Hermiston, Ore., to Wilbur, Wash. Pheromone traps are being used in Idaho, Washington and Oregon to monitor the developing situation.

Andy Jensen, director of research for the Washington State Potato Commission, is concerned but optimistic that PTW and tuber moths will not become unmanageable pests.

“Processors are doing plenty. They’re looking for the insects to keep track of which fields might have it (PTW) to make sure they ship clean,” Jensen said. “I’m optimistic, based on this winter, that it may be less of a problem this year.”

“It’s not going away,” he said. “The main thing is we in the Washington Potato Commission and the research community are putting a lot into this to understand how the industry can manage the pest.”

Jensen and Phil Hamm, a plant pathologist at the Oregon State University Extension office in Hermiston, decided to set traps in 2004 after seeing more damage from PTW in 2003.

“We set those (traps) out not knowing what to expect,” Hamm said. “We set more than 100 traps in Oregon and Washington, with 35 in Oregon. We found moths in half the 35 traps, in low numbers in May, and that really surprised us. We found some across the Columbia River, and as time progressed, we saw numbers increase. We kept 11 traps going through the whole winter. During freezing weather conditions, we still found we had huge numbers of moths into a week before Christmas.”

Hamm believes the pest is manageable.

“I don’t believe it’s catastrophic,” he said. “It will become just another management issue, such as late blight, early blight, Colorado beetle. There will be some costs to control it. The point is, it’s a new pest. We will solve this issue.”

Silvia Rondan, an entomologist at the Hermiston Extension office, is leading OSU research on PTW. Rondan is collecting specimens in Oregon, Washington, Idaho and California to determine if these populations are related or different.

“We are doing DNA tests to determine where the population is coming from, whether it has been here before or if it has been introduced from somewhere else,” Rondan said.

Idaho growers, producers and industry officials are united in their concern regarding the discovery of PTW, but all expressed support for the Idaho State Department of Agriculture (ISDA) approach.

Dave Smith, president of the Idaho Growers and Shippers Association, said his organization supports the regulatory actions taken by ISDA in concert with University of Idaho research.

Potato grower Michael Van Orden of Pingree applauds the state’s actions.

“What they did last summer was quite beneficial,” Van Orden said. “They’ve done a good job. I think that they’re going to have to monitor seed as it comes into the state.”

Frank Muir, chairman of the Idaho Potato Commission, called PTW a “very sensitive topic.”

“Several western states are affected by it. It’s a serious problem,” he said. “The ISDA has taken a very strong stance to keep PTW moth and tuberworm out of the state and we support their actions. The best action is preventative.”

Muir is effusive in his praise of how ISDA leadership has handled the situation.

“I think Pat (Takasugi, director ISDA) has done a very outstanding job in protecting Idaho’s premier crop. The key message right now is that we do not see a problem here in Idaho but we have to keep vigilant in order to keep this pest out of the state,” Muir said.

ISDA spokesman Wayne Hoffman echoed Muir’s call for vigilance.

“People need to be assured we’re being vigilant and we’re going to monitor and take necessary steps to keep this from getting out of hand,” he said. “We’re going to do additional traps this spring. We don’t want to end up in a situation where Idaho’s potato industry is on the defensive; we want to be on the offensive. The issue is protecting Idaho’s very valuable potato industry.”

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