Corn that contains proteins that protect it from insect damage has been grown in the U.S. since the mid-1990s. Known as Bt corn, because the proteins are derived from a bacterium called Bacillus thuringiensis , these plants have been widely grown by farmers.
While Bt corn has been highly effective against the European corn borer, it has been less so against the western corn rootworm, which has been documented to show resistance to the Bt proteins. In a new article in the Journal of Integrated Pest Management -- an open-access, peer-reviewed, extension journal -- the authors explain why this has occurred, and they recommend an integrated pest management (IPM) approach to address it.
In " Resistance to Bt Corn by Western Corn Rootworm (Coleoptera: Chrysomelidae) in the U.S. Corn Belt ," Drs. Aaron Gassmann (Iowa State University), Michael Gray (University of Illinois), Eileen Cullen (University of Wisconsin), and Bruce Hibbard (University of Missouri) examine why Bt corn has been more effective against the European corn borer, which tunnels in the stem of the plant, and less so against the rootworm, which attacks the roots.
First, Bt proteins intended for the European corn borer are produced at a higher dose than the ones intended for rootworms; this ensures that fewer corn borers are likely to survive, which lowers the chances of them producing offspring that may be resistant. Second, corn borer moths travel farther before mating, which increases the chances of potentially resistant insects mating with non-resistant ones that have not been exposed to Bt proteins; this lowers the chances of them producing resistant offspring. Finally, fitness costs -- or negative effects -- of resistance in rootworms appear to be low.
"One approach to IRM is not necessarily optimal for all insect pests," according to the authors, who recommend that growers use the following IPM approaches to delay further rootworm resistance to Bt corn:
The full article is available for free at:
http://esa.publisher.ingentaconnect.com/content/esa/jipm/2013/00000004/00000003/art00003
The Journal of Integrated Pest Management is published by the Entomological Society of America, the largest organization in the world serving the professional and scientific needs of entomologists and people in related disciplines. Founded in 1889, ESA today has more than 6,500 members affiliated with educational institutions, health agencies, private industry, and government. Members are researchers, teachers, extension service personnel, administrators, marketing representatives, research technicians, consultants, students, and hobbyists. For more information, visit http://www.entsoc.org .
Journal of Integrated Pest Management