New research on GM cotton is showing that the reduced caterpillar attack in Bt (Bacillus thuringiensis) cotton suppresses the production of natural defence mechanisms which fight off other pests like the cotton aphid.
Non-Bt plants respond to caterpillar infestation by producing defence compounds like terpenoids, which also protect the plant against other pests. Previous studies had linked the surge in aphids to reduced use of insecticides in Bt GM crops.
T. M. Manjunath, a consultant in agrobiotechnology and integrated pest management from India, where Bt cotton is cultivated, says: “What this study shows with Bt cotton can happen with any other insect-control measure. Infestation by aphids and other non-target pests has been seen before the introduction of Bt cotton”.