Insect Resistance Management for GE Crops: Industry Principles, Policies, and Programs

Introduction Resistance is a natural phenomenon, a result of evolution and adaptation to environment. When a pest population is exposed to a pest management tool, whether chemical, biological, or cultural, the individuals in that population that are genetically predisposed to overcome the management tool are more likely to survive and pass their genes on to the next generation. Over multiple generations, the genotypic make-up of the targeted pest population shifts from susceptibility to resistance. Insect resistance management (IRM) is the set of practices that are intended to slow this evolutionary process, delay the onset of resistance, and reduce its economic and environmental impact. In the context of agricultural biotechnology, the rate at which resistance develops in target pest populations is influenced by genetic, biological, and operational processes (Bates et al., 2005; Gould, 1998). For genetically engineered (GE) insect protection traits, operational factors include the level of mortality the GE crops cause to the pest populations, the extent to which the GE traits are adopted across the agricultural landscapes and over time, and the diversity of other crop and non-crop hosts of the target pests in the landscapes (Gustafson et al., 2006). Biological factors include the intensity of selection pressure for resistance imposed by a crop as a result of the expression of an insecticidal trait; the extent to which the insect pests use alternative host plants; the dispersal, mating, and oviposition behavior of the insects; and fitness costs associated with resistance mechanisms (Caprio, 2001). Population genetics are driven by the genetic diversity of a pest population, including the number of genes involved in resistance to an insect protection trait; the frequency of alleles that confer resistance; the level of the resistance that is achieved; and the level of resistance conferred on heterozygous insects that carry one copy of a resistance allele and one of the wild-type susceptible allele. The most widely Insect Resistance Management for GE Crops: Industry Principles, Policies, and Programs