Corn Rootworm Control Will Be Addressed in March Issue

So far control problems haven't been reported in Indiana.

Published on: Feb 10, 2012

Talk continues about the lack of control of rootworms by Bt methods bred into hybrids in western states. The primary reports of failure of control come from Iowa, Minnesota, South Dakota, Nebraska, parts of Wisconsin, and Illinois. Researchers in Iowa and Minnesota have documented many cases of lack of control.

So far the problem is linked to one genetic event, the Cry3Bb1 event- a YieldGard event. Part of the debate is whether the lack of control is true resistance from the insect to the trait or not.

While several entomologists quietly say it certainly appears to be resistance, Ken Ostlie, University of Minnesota Extension entomologist, notes that technically, as of this time, it's possible that not all of the requirements laid out by the Environmental Protection Agency to truly call an insect resistant have been met.

The fact remains that rootworms are feeding on corn in western states protected by this single genetic event. No problems have been reported so far with other events that are on the market.

The problem typically show up first on farms that are in continuous corn, or have been in corn for several years in a row, and on farms where the same Bt trait has been expected to control the insect each season.

The panel of Indiana Certified Crop Advisers in Hoosier Bug Beat and other articles in the March issue of Indiana Prairie Farmer will lay out possible actions to take. Primarily, in Indiana, it's to monitor fields, since the problem hasn't appeared here yet. There is no way to know if it will develop in Indiana or not. Fields affected in the western states have been impacted by the western corn rootworm, the same kind found here. However, except for eastern and central Illinois, most of those areas do not have the variant that lays eggs in soybean fields.

The panel also makes a strong case for crop rotation with soybeans, even though the problem hasn't shown up here. Planting corn after corn in the same field year after year, especially if you use the same genetic trait to control rootworm, puts intense selection pressure on the rootworm to seek a mutation that can survive and bust through control.

The other lesson from this, the panel believes, is that it is important to follow the refuge requirements laid out by companies. Many farmers follow refuge requirements religiously, but others have openly admitted in public settings that they don't bother with refuge.