March 30, 2007

My seed dealer said it is OK to plant YieldGard Corn Borer hybrid corn as a refuge for my Herculex I Bt corn field because they use Bt proteins with different modes of action. Is this correct?

According to the EPA-approved label which outlines requirements for using Bt corn hybrids, the refuge corn must not be a Bt corn active against European corn borer, if the Bt corn hybrid has a Bt protein active against the European corn borer. Remember, the goal of the refuge is to promote survival of European corn borers who have not been exposed to Bt protein, in the immediate area of the Bt corn field. Using a Bt corn active against European corn borer would not be an effective method to allow survival of corn borers in the refuge.

There is a kernel of truth in the original suggestion; in general, using different toxins with different modes of action has the potential to reduce resistance development. In this case however, rotating toxins is not compatible with the goals of the refuge-based resistance management plan that we are using.

Bob Wright
Extension Entomologist