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Green peach aphid.
(K836-3)
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Steaming baked potatoes, crispy
french fries, crunchy chips....Consumers love potatoes from the Pacific
Northwest. And so do insects.
With increased regulatory scrutiny of many oft-used pesticides, potato growers
are looking for alternatives to keep pests at bay.
ARS researchers at the Yakima
Agricultural Research Laboratory in Wapato, Washington, are devising new,
integrated strategies to protect potato crops. The biggest concern in the
Pacific Northwest is the green peach aphid, says ARS entomologist Lawrence A.
Lacey, because the aphid transmits leaf roll and other viruses. Leaf roll virus
can decrease yields and turn parts of the potato flesh brown, making it
unacceptable for either the fresh or processed market.
Lacey is researching two potential biological control agents: a fungus,
Verticillium lecanii, and a parasite, Aphidius colemani. The
fungus is already registered for use against several insects, but there's one
complication: The fungus and the parasite may inhibit each other.
"In a different study, my student and I showed that parasites avoided
Russian wheat aphids that were infected with fungi and that the fungi were less
likely to become established in parasitized aphids," Lacey says.
"We're investigating whether the same situation exists with these two
organisms in green peach aphids," he says.
Meanwhile, ARS entomologist David R. Horton is evaluating more-selective
pesticides. "Right now, growers use broad-spectrum insecticides. But those
are the types of chemicals most likely to face restrictions," Horton says.
"If we can find chemicals that control only aphids, for example, they
might fit in well with an integrated pest management program that also uses
beneficial insects and cultural controls such as crop rotation."
Although such selective products are available, Horton says this approach
leaves the door open for secondary pests, such as the Colorado potato beetle.
Once a grower stops using systemic insecticides, the beetle could cause
significant damage. But right now, the beetle poses a much lesser threat than
the aphid.
Lacey has demonstrated that a mixture of the fungus Beauveria bassiana
and a strain of the bacterium Bacillus thuringiensis provides good
control of Colorado potato beetle in the Northwest. Further, because the fungus
can survive in soil and in the bodies of killed overwintering beetles, the
mixture provides better long-term control than the bacterium alone.
By combining basic and applied research, the team hopes to develop a set of
tools that give potato growers more options if their preferred methods of
defense disappear.—By
Kathryn Barry
Stelljes, Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS National
Program (#304) described on the World Wide Web at
http://www.nps.ars.usda.gov.
Lawrence A. Lacey and
David R. Horton are at the
USDA-ARS Yakima Agricultural Research
Laboratory, 5230 Konnowac Pass Rd., Wapato, WA 98951; phone (509) 454-6550,
fax (509) 454-5646. |
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