Bt Corn for Corn Rootworms?

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Rod R. Youngman
Associate Professor and Extension Specialist, Department of Entomology, Virginia Tech, Blacksburg, VA 24061-0319

Well it's not here yet, but it's on the way. What I'm talking about is the long-awaited development of transgenic corn hybrids that are resistant to corn rootworms. According to a recent announcement by Monsanto Corp. in St. Louis, Missouri, they have developed a transgenic "rootworm-protected" corn product which expresses Bt proteins in corn roots in levels high enough to be toxic to corn rootworm larvae. Unlike the Bt corn hybrids currently on the market that protect against stalk and ear tunneling from European corn borer, these new "rootworm-protected" Bt corn hybrids are designed to protect corn roots from the ravages of western and northern corn rootworm feeding. Both of these rootworm species occur in Virginia, as well as other mid-Atlantic states. Research conducted by my lab in Virginia has shown that the western corn rootworm, which was first detected in Virginia in 1985, annually affects about 28% of the continuous corn acreage in the state.

In their announcement, Monsanto said that details on product efficacy, secondary benefits, resistant management, and product positioning are expected to be released soon. Monsanto stressed that much research still needs to be done in order to characterize product performance and develop appropriate resistance management strategies. Monsanto hopes to obtain EPA approval for their "rootworm-protected" Bt corn hybrids by as early as 2001.

Mycogen Corp. in San Diego, California is another prominent player in the biotechnology arena. If you recall, 1996 marked the first year that transgenic Bt corn hybrids were available to growers for controlling European corn borer, a major pest of corn throughout the U.S. corn belt and mid-Atlantic states. Mycogen Corp., in conjunction with Ciba Seeds, was the first company to market and register a Bt corn hybrid in the U.S. I visited Mycogen this past June and learned that they also have met with some success in developing Bt corn hybrids with activity against corn rootworm larvae. From an industry perspective, Mycogen speculated that Bt corn hybrids with activity against corn rootworms should be available to U.S. corn growers within five years.

Given the recent announcement by Monsanto, as well as the tremendous efforts being made in the Bt arena by other genetic engineering and large seed development companies, I fully expect that Bt corn hybrids with resistance to corn rootworms will be available to Virginia corn growers within the next five years. For more information on western corn rootworm biology, damage, and management in Virginia, please refer to VCE publication number 444-266.