FMC and Universities Join Forces on Alfalfa Weevil Research

In a unique effort, researchers from Montana State University, Oklahoma State University and the University of California Cooperative Extension, along with FMC, are partnering on a two-year research study to investigate effective insecticide application timings for alfalfa weevil control. Leading this project is Kevin Wanner, associate professor in entomology at Montana State University in collaboration with Kelly Seuhs, associate extension specialist in entomology and plant pathology at Oklahoma State University, and Michael Rethwisch, farm advisor in crop production and entomology at University of California Cooperative Extension.

Spurring this project is funding from the U.S. Alfalfa Farmer Research Initiative (USAFRI), administered by the National Alfalfa and Forage Alliance (NAFA), that recently awarded $50,000 to support the multistate research project. In addition, FMC is matching the research funding distributed by NAFA to support a graduate student position at Montana State University for the two-year study.


“Alfalfa weevil is the number one chewing insect pest of alfalfa that causes economic damage across the U.S.,” Wanner stated. “With few choices for insecticide mode of action (MOA) groups to choose from and the loss of effective pyrethroid-type insecticides due to widespread resistance to this MOA, it (alfalfa weevil) is a significant challenge for forage alfalfa producers in many areas.”

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“The partnership across academia and industry is critical right now as alfalfa growers continue to wade through so much uncertainty when it comes to managing alfalfa weevil, from timing to control options,” explained Erica Rudolph, precision agriculture field manager at FMC. “This research is a proactive approach to help the industry mitigate further resistance development and find solutions to better manage alfalfa weevil.”

The study’s objective is to create a phenology model using Arc™ farm intelligence from FMC to accurately predict when adult alfalfa weevils are moving into the field and laying eggs. To drive model development, local weather data will be utilized. The anticipated output is a blueprint that will help growers make more informed and precise application decisions to manage alfalfa weevil with greater efficacy.

On the prospect of this project, Seuhs commented, “As insecticide resistance broadens, further research efforts are needed to establish levels of resistance throughout the state (Oklahoma). The need to identify patterns of cross-resistance, examine potential for early-season timing (adult and larvae) and identify impacts of weather will be crucial in the coming years. This will arm educators, specialists and scouts with information to provide timely integrated resistance management recommendations and resources to alfalfa stakeholders.”

As part of this project, university researchers will also trial novel application timings of Steward® EC insecticide and review and verify its impact on adult alfalfa weevils. Steward EC insecticide is already established as an effective solution for managing alfalfa weevil larvae. The verification of this tool for adult alfalfa weevil is essential as alfalfa growers seek new management solutions with different modes of action to help mitigate resistance and replace chemistry, like chlorpyrifos, that has exited the market.

This multistate research project will commence May 2023 and conclude after the 2025 growing season. Findings will be available following the conclusion of the 2025 season.