Insect resistance management and integrated pest management for Bt crops: prospects for an area-wide view.

Abstract Throughout this book, several authors have reviewed the pest resistance challenges within the context of the use of genetically modified (GM) crops, the solutions that are necessary to mitigate the evolution of insect pest resistance and the continued need for effective insect resistance management (IRM). Clearly, the current selection pressure has resulted from the extensive adoption of GM crops by millions of farmers worldwide due, in part, to their real or perceived benefits. Many of the benefits of GM maize and cotton have been well documented. They include increased yields, reduced yield variability, increased economic returns to farmers, reductions in insecticide use, reductions in pesticide exposure to farm workers, the subsequent conservation of beneficial insects, and the environmental benefits resulting from less tillage. These benefits, however, are not universal for all GM crops, and several important insect pests have exhibited 'field-evolved resistance' to crops engineered to express toxins from Bacillus thuringiensis (Bt). In several cases, 'practical resistance' and yield losses have been confirmed. From these case studies, we can review the factors that often contribute to resistance and thereby develop more proactive IRM programmes that are not only compatible with integrated pest management (IPM), but are fully integrated with IPM. Several compatible IPM tactics, such as biological control and cultural controls (e.g. crop rotation) can be quite effective with Bt crops and should further reduce selection pressure. Within the context of IRM and IPM, a primary question remains: what can we learn from the case studies of Bt resistance versus longer term success in order to better design future IRM plans? In this chapter, the benefits of Bt crops are reviewed as a basis for understanding grower decision making and the rationale for Bt crop use. I then summarize the key IRM elements that are necessary to facilitate the sustainability of Bt crop use within an IPM context, and subsequently review several reasons why the goals of IRM and IPM may be best understood and implemented from a landscape, or area-wide, management perspective.