Monitoring Your Alfalfa Fields for Weevil

Cornell Cooperative Extension continues to provide programming to assist agricultural producers

By Josh Putman, Field Crops Specialist with the SWNY Dairy, Livestock, and Field Crops Program

SOUTHWEST, NEW YORK (May 22, 2020) – Cornell Cooperative Extension’s Southwest New York Dairy, Livestock, and Field Crops Program would like to remind agricultural producers to be on the lookout for alfalfa weevil in their fields this season. Alfalfa weevil is a troublesome pest of established alfalfa in New York. Newly planted alfalfa fields aren’t usually affected, but established fields can be at risk as alfalfa weevil primarily overwinters as an adult in New York.

These adults return to alfalfa fields in the spring when temperatures allow and begin to feed and lay eggs in the stems of developing alfalfa plants. In an “early” spring, weevils emerge sooner, more eggs are laid, and damage to the alfalfa plant occurs while the plant grows. In general, both the weevil and the alfalfa plant respond well to favorable spring temperatures, but at lower temperatures, alfalfa develops more quickly than the weevil. Data generated from the Network for Environment and Weather Applications and NYS Integrated Pest Management Program at two locations in Southwest New York (Dansville and Jamestown), indicate that we are below the growing degree days needed for peak (50%) occurrence of alfalfa weevil. However, scouting for alfalfa weevil is very important as it can be detrimental to alfalfa yields.

Josh Putman, Field Crops Specialist, would like to share strategies farmers can use to monitor this difficult pest. Scouting for alfalfa weevil involves walking a random pattern in the field and stopping to collect a stem every 10 steps.  Once you have 10 stems, visually inspect the stems for weevil tip-feeding injury. Count each stem that shows injury within the top three inches to determine a percentage of damaged stems.  Repeat this collection of 10 random stems five more times throughout the field for a total of 50 stems inspected.  Repeat this scouting in different patterns within the field weekly. Before first cutting, farms should take action if 40 percent or more of alfalfa stems show damage.

There are several management tools growers can use if facing weevil damage. These can include early harvest, use of a recommended insecticide, or biological control. Cornell Cooperative Extension Specialists across the state are monitoring alfalfa fields to keep growers informed of potential pest infestation. Further information about alfalfa weevil can be found through the Cornell University Field Crops Page as well as the New York State Integrated Pest Management Program.  For more information about scouting your alfalfa fields in the Southwest New York Region, contact Josh Putman at 716-490-5572 or

Cornell Cooperative Extension’s Southwest New York Dairy, Livestock, and Field Crops Program specialists are here to help provide research-based resources and support during this challenging time. Their team of four specialists include Katelyn Walley-Stoll, Farm Business Management (716-640-0522 or; Josh Putman, Field Crops (716-490-5572 or; Alycia Drwencke, Dairy Management (517-416-0386 or; and Amy Barkley, Livestock Management (716-640-0844 or While specialists are working remotely at this time, they are still offering consultations via phone, text, email, videoconferencing, and mail. They are also providing weekly updates with timely resources and connections via email and hardcopy and virtual programming.

The Southwest New York Dairy, Livestock, and Field Crops Program is the newest Cornell Cooperative Extension regional program and covers Allegany, Cattaraugus, Chautauqua, Erie, and Steuben Counties. The Southwest New York Dairy, Livestock, and Field Crops regional specialists work with Cornell faculty and Extension educators to address the issues that influence the agricultural industry in New York by offering educational programming and research based information to agricultural producers, growers, and agribusinesses in the Southwestern New York Region. They are continuing to operate remotely at this time by offering one-on-one consultations, virtual programming, and paper mailings of resources. Cornell Cooperative Extension is an employer and educator recognized for valuing AA/EEO, Protected Veterans, and Individuals with Disabilities and provides equal program and employment opportunities. For more information about this program, or to be added to their contact list, contact Katelyn Walley-Stoll, Team Leader, at 716-640-0522,, or visit their website


Photo Captions: Alfalfa weevil larvae (left) and adult (right) can cause devastating damage to alfalfa fields in NYS. Cornell Cooperative Extension Specialist, Josh Putman, shares monitoring and control strategies for farms in SWNY.


If you would like more information about this topic, please call Josh Putman at 716-490-5572 or email For more information about Cornell Cooperative Extension, contact your county’s Association Executive Director. Allegany County – Laura Hunsberger, or 585-268-7644. Cattaraugus County – Dick Rivers, or 716-699-2377. Chautauqua County – Emily Reynolds, or 716-664-9502. Erie County – Diane Held, or 716-652-5400. Steuben County – Tess McKinley,, or 607-664-2301.