Collaboration spurs solutions to alfalfa weevil woes across Western U.S.

Damage by alfalfa weevil is a serious threat to the livelihoods of alfalfa growers and those who rely on this important forage crop. Insecticide resistance in alfalfa weevil has become a major issue in many U.S. states, causing significant economic challenges.

Researchers from UC Davis and Montana State University teamed with farm advisors from UC Agriculture and Natural Resources to evaluate the problem and develop recommendations for management practices to mitigate it.

“The more we asked, the more we heard about the issue,” said Ian Grettenberger, assistant professor of Cooperative Extension in the Department of Entomology & Nematology at UC Davis. “We realized we needed to address it scientifically and from an extension standpoint. A few people, including our team, were working on it at the local level, but we wanted to dive in deep at a regional level.”

Grettenberger and Kevin Wanner, associate professor in the Department of Plant Sciences & Plant Pathology at Montana State University, were able to secure USDA funding for a regional project to determine the extent of the problem and provide stakeholders the information they needed to start managing and mitigating the resistance.

“The research first determined if reports of resistance were correct, because we always want scientific verification,” Wanner said. “We saw failure of the insecticide applications to control the pest, as well as higher numbers of the insects resulting in greater damage. It became clear that this was not a localized problem; it was relevant across the Western region.”

“It also made sense to address it together to have some project standardization,” Grettenberger added. “We wanted to generate data that were comparable across regions and could be combined, and that's what Kevin's lab has been doing.”

Most of the research has been completed and dissemination of the recommendations began in 2020. The grant project ends in September 2023, but the information will be valuable to growers for many years to come.

“It’s rewarding being able to address an issue that's so important to alfalfa producers and the alfalfa industry,” Wanner emphasized. “I’m proud that we had the foresight to tackle this as a regional problem because the impacts are greater. We've learned a lot, because the production systems and the insect development are different in different locations. The solution in Montana where it’s minus 20 or minus 30 in the winter is not the same as in Southern California.”

Partnership highlights benefits of collaboration on university research

Grettenberger said the issue demonstrates that university research is important in solving pressing pest challenges. “We serve a very specific role with the research and education,” he explained. “People in the chemical industries and the growers sometimes come at problems from different angles, and we're pushing for a long-term view of agricultural sustainability and economic viability. People have been hearing me beat the drum about insecticide resistance a lot, but it’s critical.”

Along with the importance of the research, Grettenberger values the connections they have made to carry it out. “I'm proud of the team of graduate students, undergrad students and technicians that has been doing excellent work on this project. I've also worked with a lot of farm advisors, and I've been very pleased with that experience and thankful for their help.”

Wanner said his team benefited from being able to begin their work as soon as February in the Southern California area, refining their methods from those initial experiments. “We accelerated our research by working in a regional way, because in Montana we'd be restricted to May to June.”

He also appreciated learning about the diversity of agronomy for alfalfa production. “I’m an entomologist, not an agronomist,” he said. “While there are some common management recommendations for the alfalfa weevil and other insect pests, I learned that the solutions need to be customized and specific to each region because of the climate.”

For Grettenberger, the work has underscored how difficult it is to manage insecticide resistance. “I knew that going in, but we're continuously reminded of it, both when we're putting together extension recommendations and when we get questions from people,” he said. “The landscape for alfalfa weevil management is challenging because the insecticides that are currently available are so limited. People's hands are tied in terms of what they can do.”

In addition to supporting alfalfa growers, the collaborators strive to provider a broader education about pesticide resistance. “We want to help producers manage alfalfa weevils and other pests and continue to produce alfalfa in an economically viable way,” said Grettenberger, “and our overall goal is to maintain the sustainability of pest management as much as possible, which reduces concerns about agrochemical use in our production systems.”

Wanner added, “The primary recommendation for slowing down insecticide resistance is to promote alternatives to pesticides through integrated pest management. The research and recommendations are promoting IPM, which is about reducing the reliance solely on pesticides to benefit the environment and society. These results give us scientific data to incorporate into our extension work and facilitate changing people’s practices.”

Building relationships yields opportunities for greater impact

The collaborators met through a working group that was formed to address alfalfa weevil management and was funded by the Western IPM Center, quickly realizing the potential for partnership in working on the alfalfa weevil issue. 

Wanner and Grettenberger stress the importance of collaboration in their work. “I've been lucky to find a lot of good and helpful people and it’s mutually beneficial to get more work done together,” Grettenberger said. He advises early career academics to always be open to collaboration and to continually think through all the people who potentially could be looped into projects.

“Networking is vital,” he added. “Go to meetings, look at other people's work, know what's going on so that you know how people could fit into your work or you could fit into theirs.”

Wanner added that collaboration is valuable for both career development and for funding. “A lot of funding agencies look for collaborations because they feel that they deliver more impact,” he said.

The researchers also commented on how rewarding it is to work with graduate students and train the next generation of researchers.