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Pyrethroid Resistant Soybean Aphids in ND (08/29/19)

In 2019, soybean aphids were low and present at non-economic populations in soybeans in ND. A few aphids were collected from a soybean field in Grand Forks County for the pyrethroid resistance bioassay.

In 2019, soybean aphids were low and present at non-economic populations in soybeans in ND. A few aphids were collected from a soybean field in Grand Forks County for the pyrethroid resistance bioassay. These aphids were sent to Dr. Koch’s laboratory at the University of Minnesota for rearing and testing for pyrethroid resistance. Results indicate that this population was fairly resistant to bifenthrin (Trade name Brigade 2EC and generics) with 60-70% survivorship, and two of the four lambda-cyhalothrin (Warrior II and generics) vials had single survivors while one had 50% survivorship. So, pyrethroid resistant soybean aphid populations may be established in ND or migrating into ND from other resistant areas.

This illustrated the importance of proper pest management, especially treating fields with insecticides only when necessary and at the E.T. - average of 250 aphids per plant when populations are actively increasing in 80% of field. For more information, consult the multistate extension publication, E1878 Management of Insecticide-resistant Soybean Aphid.

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Janet J. Knodel

Extension Entomologist

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