The popular new strategy of planting genetically engineered crops that make two or more toxins to fend off insect pests rests on assumptions that don't always apply, University of Arizona researchers said Thursday, citing the need for improved preventive actions.
The study is published in the Proceedings of the National Academy of Sciences.
Compared with typical insecticide sprays, the Bt toxins produced by genetically engineered crops are much safer for people and the environment, explained Yves Carrière, a professor of entomology in the UA College of Agriculture and Life Sciences who led the study.
Although Bt crops have helped to reduce insecticide sprays, boost crop yields and increase farmer profits, their benefits will be short-lived if pests adapt rapidly, said Bruce Tabashnik, a co-author of the study and head of the UA department of entomology.
"Our goal is to understand how insects evolve resistance so we can develop and implement more sustainable, environmentally friendly pest management," he said.
The recent shift to the "pyramid" strategy – inclusion of more than one toxin – to thwart further evolution of pest resistance to Bt crops will expedite resistance, researchers say.
As reported in the study, the pyramid strategy has been adopted extensively, with two-toxin Bt cotton, for example, completely replacing one-toxin Bt cotton since 2011 in the U.S.
Though many scientists agree two-toxin plants are more durable, the extent of the advantage of the pyramid strategy, however, rests on assumptions that are not always met. Using lab experiments, computer simulations and analysis of published experimental data, researchers say the new results help explain why one major pest has started to become resistant faster than anticipated.