As of July 29, we have tested a total of 768 corn earworm moths in our pyrethroid AVT (adult vial testing) program. Although the percent survivorship is down somewhat from last week, we are still seeing greater than 20% survive (see the attached line graph). Could this mean that field failures are likely? Possibly, especially if worm populations are large. Our goal is to process as many moths as we can and post these weekly updates. We are also responding to calls from crop consultants, advisors and growers. We have one reported case of a ‘less than acceptable’ level of control in a peanut field. Could some of those surviving worms have been tobacco budworms, which are known to be more difficult to control with pyrethroids? Possibly, but it is almost impossible to distinguish between corn earworm and tobacco budworm without inspecting the moth parts of the worms under magnification in lab. We do know that budworms can be in the mix, up to 30% one year when we did a lot of worm IDs. Bottom line, this is the third consecutive year that local corn earworm populations are demonstrating high levels of pyrethroid resistance. Proceed with caution and consider non-pyrethroids especially in peanut or soybean fields with a lot of worms.
Additional information: cew-avt-jul-29-2010-ppt