Bt cotton plants with the Cry1Ac protein have shown varying efficacy against field populations of the insect Helicoverpa armigera. This may cause H. armigera to evolve resistance to the Cry1Ac toxin.

In “Changes in Cry1Ac Bt Transgenic Cotton in Response to Two Environmental Factors: Temperature and Insect Damage,” Olsen and colleagues of the Commonwealth Scientific and Industrial Research Organization (CSIRO) of Australia study how changes in temperature and degree of insect damage can contribute to Bt cotton’s efficacy in the field. Their work appears in the latest issue of the Journal of Economic Entomology.

Researchers used H. armigera, a chewing insect, and the aphid Aphis gossypii, a sucking insect, to investigate how the insects could affect the crop’s efficacy. They found lower levels of Bt toxin in the cotton after infestation with H. armigera, although attack by the aphid did not affect the Bt toxin levels as dramatically. They also found that cooler temperatures lowered the efficacy of Bt cotton, while plant growth at high temperature increased it.

The study could be a baseline for future research in pest resistance management, and its techniques used to monitor changes in the efficacy of biotech crops.

Subscribers to the Journal of Economic Entomology can access the full article at
http://www.bioone.org/bioone/?request=get-document&issn=0022-0493&volume=098&issue=04&page=1382.

Other readers may take a look at the abstract at
http://www.bioone.org/bioone/?request=get-abstract&issn=0022-0493&volume=098&issue=04&page=1382.