Some GM crops, those modified with the bacterium Bt (Bacillus thuringiensis), produce natural proteins that kill pest insects. Bt crop farming has resulted in a sharp reduction in the spraying of pesticides. But Bt crops are not without critics. One repeatedly cited concern is that pests could over time develop resistance to these proteins, making Bt plants ineffective and requiring additional spraying down the road.
A new study out of Cornell University and published in the journal PLoS One concludes that the combination of natural enemies, such as ladybeetles, with Bt crops, delays a pest’s ability to evolve resistance to these insecticidal proteins.
“This is the first demonstrated example of a predator being able to delay the evolution of resistance in an insect pest to a Bt crop,” said Anthony Shelton, a professor of entomology at Cornell University’s New York State Agricultural Experiment Station, and a co-author of the paper, in a statement:
Bt is a soil bacterium that produces proteins that are toxic to some species of caterpillars and beetles when they are ingested, but have been proven safe to humans and many natural enemies, including predaceous ladybirds. Bt genes have been engineered into a variety of crops to control insect pests.
Since farmers began planting Bt crops in 1996 with 70 million hectares planted in the United States in 2012, there have been only three clear-cut cases in agriculture of resistance in caterpillars, and one in a beetle. “Resistance to Bt crops is surprisingly uncommon,” said Shelton.
To delay or prevent insect pests from evolving resistance to Bt crops, the U.S. Environmental Protection Agency promotes the use of multiple Bt genes in plants and the practice of growing refuges of non-Bt plants that serve as a reservoir for insects with Bt susceptible genes.
“Our paper argues there is another factor involved: the conservation of natural enemies of the pest species,” said Shelton. “These predators can reduce the number of potentially resistant individuals in a pest population and delay evolution of resistance to Bt.”
Related on the SLP
The research seems to suggest that even the most advance GMO plants can still benefit from the traditional methods of integrated pest management.
Additional Resources:
- GM technology an aid in the ‘long, hard fight’ against Texas boll weevil, Southwest Farm Press
- Researchers confirm Bt corn’s benefits aside from pest resistance, Crop Biotech Update (ISAAA)
- GM cotton in India has probably reduced farmer suicides not caused them, Genetic Literacy Project
