Defining Terms for Proactive Management of Resistance to Bt Crops and Pesticides201

Abstract

Evolution of pest resistance to pesticides is an urgent global problem with resistance recorded in at least 954 species of pests, including 546 arthropods, 218 weeds, and 190 plant pathogens. To facilitate understanding and management of resistance, we provide deÞnitions of 50 key terms related to resistance. We conÞrm the broad, long-standing deÞnition of resistance, which is a genetically based decrease in susceptibility to a pesticide, and the deÞnition of “Þeld-evolved resistance,” which is a genetically based decrease in susceptibility to a pesticide in a population caused by resistance on pest control can vary from none to severe.WedeÞne “practical resistance” as Þeld-evolved resistance that reduces pesticide efÞcacy and has practical consequences for pest control. Recognizing that resistance is not “all or none” and that intermediate levels of resistance can have a continuum of effects on pest control, we describe Þve categories of Þeld-evolved resistance and use them to classify 13 cases of Þeld-evolved resistance to Þve Bacillus thuringiensis (Bt) toxins in transgenic corn and cotton based on monitoring data from Þve continents for nine major pest species.Weurge researchers to publish and analyze their resistance monitoring data in conjunction with data on management practices to accelerate progress in determining which actions will be most useful in response to speciÞc data on the magnitude, distribution, and impact of resistance