Alfalfa weevil

The larvae and adults of alfalfa weevil (Hypera postica) are the primary defoliators in alfalfa. Heavy infestations can reduce tonnage and forage quality. Scouting for alfalfa weevil relies on predicting activity based on degree day accumulation and looking for weevils once benchmark degree days are met.

alfalfa weevil larvae in a sweep net and a plant with heavy feeding injury
Left: alfalfa weevil larvae in a sweep net. Right: in the same field, heavy alfalfa weevil feeding caused a silver appearance on the leaves. Photos by Angie Rieck-Hinz.

An encyclopedia article details alfalfa weevil identification, biology, plant injury, scouting, and management. This includes how to track growing degree days and a step-by-step sampling plan for larvae.

Alfalfa weevil encyclopedia article

The Iowa Environmental Mesonet hosts a Pest Forecasting page where growing degree days for alfalfa weevil development may be tracked. 

Track alfalfa weevil development

Annually, spring scouting alerts for Iowa are posted on the Integrated Crop Management News page. Throughout the growing season, additional updates on alfalfa weevil activity may be posted on ICM News or on the Integrated Crop Management Blog page.

If you would like to receive timely alerts of alfalfa weevil activity in Iowa via text messaging, sign up for the Iowa Pest Alert Network!