By SEAN ELLIS
The Environmental Protection Agency has again granted Idaho and Oregon onion growers emergency exemptions to use an insecticide designed to control thrips.
Thrips, which are a vector for iris yellow spot virus, are a major concern to onion growers in the region, said Stuart Reitz, a Malheur County crop systems extension agent with Oregon State University.
"It's probably the number one pest problem our onions growers have," he said.
The EPA's approval of the emergency requests to use the insecticide Movento extends to Oregon farmers who grow dry bulb onions in Clackamas, Klamath, Marion, Malheur, Morrow and Umatilla counties. In Idaho, it applies to Ada, Canyon, Gem Owyhee, Payette and Washington counties.
In both states, the exemption is effective immediately and lasts until Sept. 15.
During feeding season, thrips stress onion plants and can result in reduce bulb sizes, "but where we really get into trouble with them is when they spread yellow spot virus," said Mike Thornton, superintendent of the University of Idaho's Parma Research Center.
"Movento is one of the tools we absolutely have to have to keep thrips populations low enough to prevent the spread of the virus," he said.
The EPA is expected to fully register the product this year, said Oregon farmer Paul Skeen, president of the Malheur County Onion Growers Association.
However, farmers weren't certain full registration would occur in time for this year's growing season "so we thought we better get ahead of things and get another emergency exemption to cover our bases," he said.
Thrips have built up resistance to some other insecticides and Movento has proven effective in helping to control them, Reitz said.
"Movento is one of the few insecticides that has been effective against onion thrips," he said.
Onion growers in this region usually start to see increased thrips populations in mid to late May if there is a warm spring or in early June if spring weather is cool, said Thornton, who added that growers should spray for the insects while populations are still low.
"We like to see guys spray when there are between one to three thrips per plant," he said.
The emergency exemptions come with several restrictions and Reitz said the most important one is that a limit of 5 ounces per acre of the product can be applied per application with a crop season maximum of 10 ounces per acre.
The EPA also requests that beekeepers be notified prior to applying the product when possible.