Dose Responses of Field Populations of Alfalfa Weevil from Various Western States to Lambda-Cyhalothrin® Using a Feeding and Contacting Assay

Insects, including alfalfa weevil (AW), are known for their genetic ability to develop resistance to insecticides. In a population of an insect species, there may be a few individuals that carry the genes for resistance to a chemical. Upon exposure to insecticides, insects that do not carry the resistance genes die, thus allowing the individuals with the resistance genes to survive and reproduce, creating more resistant insects. With every subsequent generation and continued selection, the number of resistant insects increases; therefore, the insecticide becomes less effective in controlling the pest population. Ayman Mostafa and Kyle Harrington of the University of Arizona Cooperative Extension Field Crops IPM Program investigated lambda-cyhalothrin (Warrior II™) against AW to test for any resistance by comparing the dose response of field populations of AW from seven states using feeding and contacting assay. The results of these experiments will be helpful to growers and the agriculture industry in the western region and around the nation as they decide which insecticides to use on their crops and which ones are most effective.

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