Bt plants are genetically engineered to produce insect-specific toxins. They target specific insect pests, but the researchers wanted to determine how these plants influence non-target insects in the environment.

To find out, scientists from ARS collaborated with researchers at the University of Nebraska at Omaha, Iowa State University and the U.S. Environmental Protection Agency. Steven Naranjo, a research leader at the ARS Arid Land Agricultural Research Center in Maricopa, Ariz., and Jonathan Lundgren, an entomologist at the ARS North Central Agricultural Research Laboratory in Brookings, S.D., contributed to the work.

The scientists compared the abundance of groups of non-target insects. They first compared the abundance of these insects in Bt plants and non-Bt plants without any insecticides. They also compared the insect populations in both types of plants treated with insecticides. And they compared the non-target insect populations in Bt plants without insecticides versus the populations in non-Bt plants treated with insecticides.

They formed these groups of non-target insects with data drawn from a modified version of a public database created by Santa Clara University biologist Michelle Marvier and colleagues. The toxins examined included Cry1Ab and Cry3Bb in maize, Cry3A in potato and Cry1Ac and Cry1Ab in cotton.

The researchers observed considerable variability in the effects of Bt cotton and maize plants on non-target insects. However, the data within the groups were fairly consistent. The most influential factor was the insecticide applied. Collectively, insecticides such as pyrethroids, organophosphates, carbamates and neonicotinoids had larger negative impacts on non-target insects than did the Bt plants.

The researchers concluded that when it comes to killing non-target insects, no treatment at all has the least impact. Bt plants have considerably less impact on non-target insects than do conventional insecticides. Also, insecticides affect insect populations uniformly, regardless of whether they?EUR??,,????'?????<

Source: Science Daily