What is in this article?:
- Resistant earworms, budworms likely in North Carolina soybeans
- Looks like resistance
- Steward promising
• Since the spray was a full rate of a pyrethroid, it is likely these insects are resistant to this chemical.
• We simply cannot predict the areas in which pyrethroids will fail.
• Weknow we have resistant worms in our system. The safe bet is to spray a chemical other than a pyrethroid.
Looks like resistance
The disturbing fact was that 75 percent of the remaining worms were corn earworm. Since the spray was a full rate of a pyrethroid, it is likely these insects are resistant to this chemical.
Jack Bacheler has a somewhat different perspective, identifying worms from soybeans and peanuts that ranged from 90 percent to 100 percent tobacco budworm in the Rocky Mount area. Based on these findings, we are concerned about pyrethroid spray failures.
Last year, I tested moths for pyrethroid tolerance, measuring over 50 percent surivorship in one area and 0 percent survivorship from a trap 5 miles away. This, combined with our experience with spray failures, tells us we simply cannot predict the areas in which pyrethroids will fail.
You could spray one field and have great control, drive down the road and have a complete failure, due to presence of tobacco budworm, resistant corn earworm, or both.
Because moths flights have been so low this year, I have only been able to test moths once (this past Monday) for pyrethroid tolerance — despite sampling 3 times a week since June.
From a five trap loop in Washington County, I found, on average, 13 percent moths that survived a night in a pyrethroid-treated vial. In contrast, Ames Herbert, in Suffolk, Va., is finding surivorship around the 30 percent range.
In summary, we know we have resistant worms in our system. The safe bet is to spray a chemical other than a pyrethroid. The diamides, like Belt and Prevathon are some examples.
Syngenta has a new registration for Besiege, which is a pre-mixed product containing the active ingredient of Prevathon, plus a pyrethroid (lambda-cyhalothrin, aka Karate).
Blackhawk (Tracer) offers a unique chemistry class, the spinosyns, and is highly effective against corn earworm.