I’m expecting our corn earworm flight to start kicking off this week. Given the fair amount of late-planted soybeans in the state, we need to be alert for infestations in soybean during August. Normally, our worst infestations of corn earworm in soybeans occur in the Mississippi River bottoms, but they can potentially occur anywhere. The recommended treatment threshold for corn earworm in soybeans is 9 larvae per 25 sweeps.

Against high infestations, Belt SC, Prevathon, or Besiege will provide extended residual control. I’ve also had good results with Steward and Tracer, although you should expect less residual control. Avoid the pyrethroid insecticides if infestations are well above threshold. Their performance has been inconsistent in recent years, and they do not provide effective residual control more than 7 days (less if it rains). 

A new product, Intrepid Edge, may be worth looking at on a limited basis. It is a pre-mix of Intrepid and spinetoram (e.g., Radiant). However, I’ve not tested this product against corn earworm. It is labeled at a rate of 4 – 6.4 oz/acre. This should be an excellent treatment for soybean loopers, but I’m concerned the spinetoram rate is too low for corn earworm.