Friday, August 13, 2010

Corn Earworm Pressure In Flowering Soybeans - When Do You Treat?

To date, this has been one for the records in terms of corn earworm pressure in soybeans. Many of our fields have been treated, although most are still in the flowering/late flowering stage.

We do not have thresholds for flowering beans but know that high numbers of worms can do too much damage by eating all the flowers which can result in delayed maturity.

What's next for these fields? Will earworms recycle to present another threat to podding fields?

My guess is, yes, at least some percentage of fields may need to be retreated. The decision to retreat should be made based not on rumor, seeing spray rigs running in the neighbor s field, or conversations at the diner, but based on knowledge that thresholds have been met.

Growers cannot afford to make unnecessary sprays, especially with low yield potential and having already paid for one application. And, if a pyrethroid was used the first time we would strongly recommend that these second applications be non-pyrethroids.

If you have treated with Karate, Baythroid, Endigo, Brigade, Bifenthrin, Tombstone, Sniper, Mustang Max, Hero, Proaxis, or Leverage you have treated with a pyrethroid. In our field trials we are having good success controlling worms with relatively low rates of these non-pyrethroids (e.g., Steward at 4.6 oz and Larvin at 10 oz). But even at these rates, the cost is more than the pyrethroids.

From Ames Herbert, Virginia Extension Entomologist

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