Predators Delay Pest Resistance to Bt Crops

Scientists at Cornell University reported that the combination of natural enemies, such as ladybeetles, with Bt crops delays a pest's ability to evolve resistance to Bt insecticidal proteins. According to Anthony Shelton, co-author of the study, their findings is the first reported case of predator being able to delay the evolution of resistance in an insect pest to a Bt crop. In the study, the researchers set up large cages in a greenhouse where each cage contained Bt broccoli and refuges of non-Bt broccoli. They studied populations of diamondback moth larvae, a pest of broccoli, and their natural enemies, ladybird beetles, for six generations. Cages contained different combinations of treatments with and without predators, and with and without sprayed insecticides on the non-Bt refuge plants.

Results showed that diamondback moth populations were reduced in the treatment containing ladybird beetles and unsprayed non-Bt refuge plants. It was also observed that resistance to Bt plants evolved significantly slower in this treatment. In contrast, Bt plants with no refuge were completely defoliated in treatments without ladybirds after only four to five generations, showing rapid development of resistance in the pests. In the treatment with sprayed non-Bt refuge plants and predators, diamondback moth populations were reduced, but the larvae more quickly evolved resistance to the Bt plants.

Based on the results, the effectiveness of Bt plants in controlling the pest population, the lack of effect of Bt on the predators and the role predators play in delaying resistance to Bt plants in the pest population.

The research is published in the open-access journal PLoS One.

Read the media release at http://mediarelations.cornell.edu/2014/03/04/predators-delay-pest-resistance-to-bt-crops/.