Evaluating Efficacy of Stubble - Applied Insecticide Treatments for Alfalfa Weevil Control in Oklahoma
ISSN 2158-9429
Volume 17, Issue 2 - December 2024
Editor: Linda Chalker-Scott
Abstract
Abstract
Alfalfa Medicago sativa L. (Fabales: Fabaceae) is the nation’s third most valuable field crop. In Oklahoma, alfalfa is also highly valued and ranks in the top three most economically important field crops. Insecticide resistance poses a significant risk to forage alfalfa production in the United States. The alfalfa weevil Hypera postica Gyllenhal (Coleoptera: Curculionidae) is an economically damaging pest of alfalfa in North America. Due to insect resistance to pyrethroids, limited alternative mode of action (MoA) groups are available for alfalfa weevil control. The objective of the study was to evaluate efficacy of stubble - applied insecticide treatments for alfalfa weevil control in Oklahoma. A field trial was conducted in Stillwater, Oklahoma (Payne County). Treatments consisted of five commercial insecticide formulations applied on alfalfa, as stand-alone applications or tank mixes at maximum label rates, early stubble, and prior to traditional threshold timing. Insecticide treatments, stand-alone or tank mix, in the stubble-treated field trial failed to provide expected control (90%) targeting alfalfa weevil larvae. No treatment provided control greater than 58%. Results from this study suggest stubble - applied treatments for alfalfa weevil control were not effective. There is a need for future research to explore if scouting protocols, based on the adult life stage, could be an alternative strategy.
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