Alfalfa weevils (Coleoptera: Curculionidae) in the western United States are resistant to multiple type II pyrethroid insecticides.

The alfalfa weevil (Hypera postica Gyllenhal (Coleoptera: Curculionidae)), a key pest of alfalfa (Medicago sativa L. (Fabales: Fabacae)) across the US, has developed resistance to pyrethroids lambda-cyhalothrin and zeta-cypermethrin in at least 6 western US states. Unfortunately, 6 pyrethroid active ingredients represent most commercial insecticides registered for alfalfa weevil control in forage alfalfa systems.

First Report of Alfalfa Weevil (Coleoptera: Curculionidae) Resistance to Lambda-Cyhalothrin in Montana.

Forage alfalfa (Medicago sativa L. [Fabales: Fabacae]) is a major agronomic crop grown nationally and Montana ranks highly in acres harvested. The alfalfa weevil (Hypera postica Gyllenhal [Coleoptera: Curculionidae]) is the primary defoliating pest that requires insecticide applications to prevent yield loss, particularly pyrethroid active ingredients (a.