ISU researchers are working on possible solutions to a western corn rootworm that is resistant to genetically modified corn in Iowa fields.

Bacillus thuringiensis (Bt) produces crystals of protein, which are toxic to many species of insects. Insects that eat plants with Bt crystals die because the walls of their guts break down. In order to reduce losses from pests, some plants, like cotton, have been modified with short sequences of Bt genes to express the crystal protein and protect themselves from insects without external Bt and/or synthetic pesticide sprays.

Aaron Gassmann, assistant professor of entomology, found why the four fields in Iowa suffered from western corn rootworm injury.

“The common pattern that was observed in the fields with problems was consecutive planting of the same type of Bt corn for at least three seasons,” Gassmann said. “The consecutive use of the same type of transgenic or Bt corn seems to be leading to this problem.”

The best-case scenario is to use proper rotation — moving the field out of corn production to something else like soybeasn, which could break the life cycle of the corn rootworm.

Other practical solutions are to change the type of seeds by using different types of transgenetic corn or to use different ways of killing the corn rootworm such as combining with different pesticides. Also, non-transgenic corn with pesticide is an operable plan.

These strategies make changes to the environment that help prevent worms from adapting Bt toxins and any other new practices.

Transgenic technology makes pest management easier. However, Gassmann pointed out that if people rely solely on the technology and use the same management strategy for years, problems may rise. Pests have the ability to adapt human practices.

Chad Hart, assistant professor and grain markets specialist of economics, said the western corn rootworm is both “a big deal and not a big deal. It is a big deal because we do find the rootworm that is resistant to Bt technology, and it does have impact on corn farming,” he said.

However, Bt technology is only one pest-resistance pathway. There are other techniques to keep rootworm in the bay. These pathways are already available for the farmers to react on the emergence of western corn rootworm. Rootworm does not have major effect on corn market, but only highly localized effect, which is under control. We should certainly watch on the evolving of pests and develop proper techniques to reduce the damage, Gassmann said.

Additionally, many articles use “Superbug” to describe the western corn rootworm, but Gassmann said the term is inaccurate. Usually, when the pests adapt to something (in this case Bt corn), it actually becomes weaker in other environments. The increased ability to survive in an environment comes from the cause of decreasing ability of survival in other environments. Therefore, the western corn rootworm is more like a specialized bug that developed a new way of surviving, not a superbug that can survive anywhere.