George B. Frisvold
University of Arizona
Jeanne M. Reeves
Cotton Incorporated

While crop biotechnologies deployed worldwide with herbicideresistant (HR) or insect-resistant (IR) traits have provided significant economic and environmental benefits, these benefits are threatened by the evolution of insect and weed resistance. This article examines why field-level resistance has not posed a problem for IR crops but has become a growing problem for HR crops. Key factors include compatibility of the technologies with integrated pest and weed management and the regulatory and institutional setting in which they were deployed. Transgenic crops will be more sustainably deployed if they are embedded in integrated pest and weed management with strong, outward extension linkages to farmers and backward linkages to research institutions. Public and private plant breeding can play a critical role in developing stacked traits that reduce overreliance on single chemical compounds or toxins. Extension can serve two important functions along with its traditional role of information provision: (a) facilitating farmer collective action for area-wide resistance management and (b) providing government agencies with information needed to increase the flexibility and cost-effectiveness of resistance management regulations. The article concludes by discussing some implications for resistance management in developing countries.

Key words: Resistance, herbicides, IPM, weed management, Bt cotton.