Corn earworm moths already showing high levels of pyrethroid resistance in Virginia

From Ames Herbert via the Virginia Pest Advisory (

As of the end of this week (June 29, 2012) we have tested 372 corn earworm (CEW) moths for pyrethroid susceptibility and have a season average of 31.2% surviving the AVT (adult vial test) challenge (see the attached line graph). We had one sample with over 40% survivorship. These are high numbers for the beginning of the season and compare pretty well to what we had at this time in 2011, if not a bit higher. What does this tell us? We cannot claim pyrethroid resistance based on this kind of random survey of moths, but historically, when we see survival numbers of about 25-30% or higher, we can expect some pyrethroid control problems, especially if moth fights are heavy, and the weather turns dry. That combination would almost guarantee control problems. But, if CEW populations reach only low to moderate numbers and the season continues to get plenty of rainfall, field failures will not be nearly as common. With loss of Larvin, an effective non-pyrethroid for controlling CEW, growers will need to turn to other non-pyrethroids like Belt, Coragen (Prevathon**), Steward, or combinations that include a pyrethroid plus a non-pyrethroid either tank mixed (like a pyrethroid + Orthene) or as a product (like Besiege** which contains Karate and Coragen). (**note, the registration status of these products is not certain at this point)

One thought on “Corn earworm moths already showing high levels of pyrethroid resistance in Virginia

  1. Ames Herbert

    We have tested another 166 moths since last weeks report and are seeing some improvement, maybe. This recent batch showed a drop to only 17.4 percent surviving the AVT challenge, making a 28.2 percent average survivorship for the seasonal 538 total testeddown a bit from the 31.2 percent survivorship reported last week. Before giving a sigh of relief, data from last season showed an almost identical pattern with the same slight drop in early June of 2011 followed by a peak exceeding 50 percent survivorship. Stay tuned for more updates. We are also finding what appears to be a high percent of sweet corn ears infested (we pulled a bunch this week at the research center for our respective family 4th of July cookouts). We will be initiating our annual field corn survey soon which gives us the best idea of the size of the CEW population we will be dealing with.


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