Pasture and Forage Minute: Alfalfa Weevil Resistance to Pyrethroids, Expectations for Old Hay

Feb 12, 2026

By Ben Beckman and Samantha Daniel

Alfalfa Weevil Resistance to Pyrethroids

Alfalfa weevil is a serious pest of alfalfa and can cause significant damage, usually in April and May before the first cutting. Reports of reduced efficacy of pyrethroids in Nebraska as well as confirmed resistance to pyrethroids in several western states led to a project in 2025 to determine if Nebraska weevil populations are developing resistance.

During the 2025 season, alfalfa weevil larvae were collected from 12 counties across the state, including the Panhandle, southwest, south-central and eastern Nebraska. The larvae were shipped live to the PREEC Entomology Lab in Scottsbluff, where they were exposed to the label rate of two types of pyrethroid insecticides: lambda-cyhalothrin and permethrin.

The study found that five of the 12 weevil populations had 90% or less mortality when exposed to lambda-cyhalothrin. This indicates that some Nebraska weevil populations may be losing susceptibility to lambda-cyhalothrin. In contrast, all 12 weevil populations had a 100% mortality rate when exposed to permethrin.

What does this mean for alfalfa weevil management?

Currently, there are only two insecticide modes of action available for chemical control of this insect: pyrethroids and indoxacarb (Steward). Because of this, resistance management and the use of alternative control methods is critical. Make sure to scout and only spray when thresholds are reached, use the highest labeled rates, rotate control measures to delay resistance development.

Source : unl.edu

Video: Season 7, Episode 1: Managing Risk and Seeing Opportunities in U.S. Pork Production

Today’s episode features three guests discussing the similarities and differences between pork production in the United States and Brazil, along with strategies for managing risk in today’s industry while recognizing and acting on opportunities. First, Dr. Anne Caroline de Lara, executive manager of live pig production at Seara Alimentos, a JBS company in Brazil, is joined by Dr. Matthew Turner, head of operations for JBS Live Pork. Together, they discuss how labor, climate and ventilation challenges vary between Brazil and the United States, while underscoring their shared commitment to raising healthy pigs. They also point to lessons producers in both countries can take from one another’s systems and on-farm experiences. Then, Brady Reicks, risk manager at Reicks View Farms, shares his perspective on risk management, drawing from his background in markets and his transition into farming. He discusses how protecting margins varies by operation and offers practical approaches producers can use to make marketing and business decisions with greater confidence rather than hesitation.

Both conversations were recorded at recent industry events focused on swine livability, including the International Conference on Pig Livability and Iowa Swine Day.