Here is an update on lesser cornstalk borers from Clemson peanut specialist Jay Chapin.
Dryland peanuts remain very spotty. Although we have a good crop set in some areas, we also have plenty of moderate to severe drought stress fields with reduced pod count, slack or poppy pods, and lesser cornstalk borer damage.
With most of the crop in the 90 – 110 DAP interval, the last fungicide application is being made. Velvetbean caterpillar remains as a threat to cause defoliation below the lakes and spider mites where ever there is continued drought stress.
Lesser Cornstalk Borer Control Possibility
Unfortunately some S. C. peanut growers will have their first experience with lesser cornstalk borer damage this year. Moths can be found laying eggs in drought stressed fields especially on the lightest soils.
For many years the only partially effective control of lesser cornstalk borer (other than irrigation, which is hands-down the best treatment) has been Lorsban granular. Lorsban granular treatment has a lot of practical limitations including almost a guarantee of setting off spider mite and foliage feeding worm problems.
Recent research (Dr. Mark Abney, UGA) has indicated that one of the new diamide insecticides, chlorantraniliprole, which is the active ingredient in Coragen (3.5 – 5 oz) and Prevathon (14 – 20 oz) may be effective as a foliar treatment.
Besiege also has the same a.i. along with lambda-cyhalothrin (Karate). The Besiege jug mix has definite advantages for certain pest situations (worm and hopper control), but under drought stress where spider mites are a threat, the Coragen or Prevathon may be a better choice.
Prevathon seems to be more available than Coragen, and perhaps priced more for the row crop market. Best results were obtained with the higher rate of Prevathon and that’s not cheap, but may be worth it.
We don’t know how consistent results are with Prevathon against lesser cornstalk borer, but there aren’t really any alternatives to attempt control. On drought stressed peanuts still with good yield potential, I would try Prevathon if I saw lesser cornstalk borer moths flushing when I walked the field. I would at least use the lower rate for control of velvetbean caterpillar or other worms in drought stressed fields because it might suppress lesser cornstalk borers. Prevathon, like all the diamide insecticides, has excellent residual activity against all foliage feeding worms and therefore will put an end to concerns about velvetbean caterpillar.
How do you recognize lesser cornstalk borer moths? Easy. If you see lots of small (1/4”) moths flushing as you walk through a drought stressed peanut field, you are seeing lesser cornstalk borer moths, and the females are there to lay eggs. Unlike other common peanut pest moths, the tan or charcoal moths rest with their wings straight back along the body.