High Alfalfa Weevil Damage
Photo Credit: Krista Hamilton, Department of Agriculture, Trade & Consumer Protection, Wisconsin
Alfalfa weevil is expected to impact folks in the Southern region this week (~May 22nd), next week in the Central region (~May 27th) & in the Northern region (~May 27th) — so it is time to go scout your alfalfa fields for plant damage!
Critical Economic Information
The economic threshold for insecticide treatment occurs when 40% or more of your stems are damaged AND you are more than 7 days from your harvest date. Please note: the WI threshold is NOT related to the number of larvae in your sweeps.
For those fields with significant damage, scout regrowth thoroughly to ensure weevils are not feeding on new stems or crown buds.
Chemical control: Please note that alfalfa weevil can quickly become resistant to insecticides, so chemical rotation is important. See Table 1 here for more information.
Scouting
To scout for alfalfa weevil damage, walk the field in a W-shaped pattern. Examine at least five alfalfa stems in five separate areas of your field. See here for more information.
Learn more with UW-Madison Extension’s Alfalfa Weevil Resource, and DATCP’s Field Note’s section on Alfalfa Weevil.
If you found this information on the web, you can sign up for insect pest text alerts here.
