Do Bt crops contribute to IPM?

As of 2009, transgenic crops were grown on 134 million hectares worldwide in 25 countries. Transgenic Bt crops, which produce various Cry proteins from Bacillus thuringiensis and confer resistance to lepidopteran and coleopteran pests, are commercially grown in 23 countries on approximately 50 million hectares. Bt crops can be viewed as a convenient way to deliver selective insecticides or more appropriately as host plant resistance. In either case, because Bt crops may sometimes be used in a preventative manner without a determination of need, it has been suggested that they are not being used within an IPM framework. However, we need to view IPM as broadly consisting of a suite of avoidance tactics (e.g., biological control, cultural control, host plant resistance) that underlie more conventional prescriptive control based on need. This broader view forces realization that Bt crops are only a single tactic in the IPM toolbox and that careful integration of tactics are needed to strategically manage the pest complex of any crop. An example from the Arizona cotton system will be used to illustrate how the integration of Bt cotton into the whole system has contributed to massive reductions in insecticide use and greater sustainability over the last 15 years.