Alfalfa Weevils are Active Statewide

Alfalfa weevil larval activity is beginning its peak activity across the state. Alfalfa weevil feeding activity is driven by the accumulation of growing degree days (GDD) and reaches their peak feeding and damage when heat units for the area are between 325 and 575 (accumulation from a base of 48°F starting January 1^st). The warm temperatures over the past week have contributed to a significant jump in GDD and ramped up alfalfa weevil larval feeding. As of writing this (Jan. 1 – April 28), heat units range from 499 in southcentral Ohio to 267 in northeast Ohio.

Scouting is key to the proper management of alfalfa weevil. Scouting is an easy process and was covered in an article written earlier this spring “Alfalfa Weevil Scouting and GDD.” Additionally, this video resource outlines the process: Alfalfa Weevil Scouting Video.

To monitor alfalfa weevil development, county educators from across the state scout fields in their respective counties as shown in Table 1.

Table 1: County alfalfa weevil scouting reports for April 22-28

The county averages listed don’t warrant utilizing a control method, but individual fields can be highly variable. Scout your fields and use Table 2 to help make management decisions.

For more information on control methods consult the OSU and MSU “Field Crops Insect Pest Management Guide” (https://aginsects.osu.edu/extension-publications/msuosu-ipm-guide)