Lannate and Larvin Resistance in Beet Armyworms from the Low Desert Regions of Arizona and California

Abstract

Beet armyworm populations were collected in 1996-97 from spinach, melons, lettuce and alfalfa in Arizona and California, and tested for resistance to topical applications of Lannate. Resistance levels were found to be low to very high. The lowest level of resistance detected came from Blythe, CA, having no detectable resistance to Lannate, and from Parker, AZ, having a resistance level of approximately 24 fold. The highest level of resistance detected was a 685 fold increase, from a population collected from alfalfa in Imperial County, CA. In Yuma, larvae collected from alfalfa following an insecticide application that included Lannate, was 4.43 fold more resistant than the pre-application population. Only very low levels of resistance were found to Larvin, and no evidence of cross -resistance between Lannate and Larvin was found. Larvae resistant to topical applications of Lannate were found to be susceptible to Lannate given orally. Lannate resistance appears to be due to cuticular penetration and/or cuticular metabolism.