Friday, August 13, 2010

Tobacco Budworm In Mix In Both Soybeans And Peanuts

We have confirmed that tobacco budworm is in both soybean and peanut fields.CLICK HERE to see a table with the percentages of each, corn earworm (CEW)/tobacco budworm (TBW), from 8 fields in Virginia and northeast North Carolina.

Note that the IDs were based on the differences in jaw construction in the two species (mandibular identification), which means the jaws of each worm (240 total) had to be dissected and inspected under high magnification.

Most collections came from fields that had been recently treated by the grower with either Baythroid XL or Karate Z.

We also included the day post treatment that the worms were collected. With the exception of collections from two untreated fields, these worms represent pyrethroid escapes .

Unfortunately, we do not have pre-treatment samples so do not know what the species ratio was prior to application. Escapes ranged from 4 to 86% TBW. Were these selected for by the pyrethroid sprays, as TBW is known to be harder to kill with pyrethroids?

That would be our best guess. In the future, knowing the ratio of CEW/TBW could be critical to achieving good control by guiding the insecticide choice. If TBWs are known to be in the mix, it might tip the scale in favor of using the more effective, but more costly, non-pyrethroids.

In soybeans, that means Steward, Larvin, or Tracer. In peanuts, Steward or Tracer. Soon there may be some new options. Our field plot research is showing a lot of promise for Bayer CropScience s Belt insecticide, Dupont s Coragen insecticide, and a few others. Belt has just received a label for use in soybeans and some other legumes (CLICK HERE for details).

When will this group of products be available and what will they cost? Good questions.

From Ames Herbert, Virginia Extension Entomologist

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