Bacillus thuringiensis (Bt)
Organic farmers have expressed concerns about the widespread use of plants engineered to contain Bt. They note that normal applications of Bt — one-time, high-level doses — may kill some nontarget insects, but plants with Bt in their stalks, leaves and pollen can poison nontarget insects — including beneficials — throughout the growing season. Not only may Bt crops potentially reduce biological diversity, say ecologists and organic growers, but these engineered plants also increase the risk of pests developing resistance. That would remove a major weapon in an organic farmer’s arsenal.