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Soybean aphids gain resistance to pyrethroid insecticides

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AUDIO: Erin Hodgson, Iowa State Extension entomologist

A common field pest becomes more difficult to treat within recent years.

Iowa State Extension reports soybean aphids have been in Iowa since 2001. Extension entomologist Erin Hodgson says Extension staff have watched soybean aphids gain resistance to pyrethroids.

“For the last couple growing seasons, there have been populations in Minnesota, South Dakota, North Dakota and one location in Iowa where we (have) identified pyrethroid resistance in commercial fields,” Hodgson said. “This means if you apply pyrethroids, aphids are likely to survive that exposure.”

A decent amount of farmers use pyrethroids, common insecticides, to combat pests, such as soybean aphids. As soybean aphids gain pyrethroid resistance, it becomes more challenging to treat the common pests. If you suspect pyrethroid resistance in your field, Hodgson encourages you to avoid pyrethroids and their mode of action.

“The other common choice they would have available to them would be an organophosphate,” Hodgson said. “I’d recommend using that if they’re at all hesitant about a pyrethroid.”

Unfortunately, pyrethroid resistance is not preventable. However, Hodgson says farmers can delay resistance by utilizing the few tools available and scouting fields frequently.

“My first recommendation is to scout,” Hodgson said. “Scout on a regular basis to see what you have, not only for soybean aphids, (but) other pests and plant pathogens you have in the field as well. If you have aphids that (have) built up a treatable threshold, try and known down the population best you can with a well-timed insecticide.”