Alfalfa Weevil

Common: Alfalfa Weevil

Scientific: Hypera postica

Crop Hosts: Alfalfa, yellow sweet clover.

Identification and Life Cycle: The beetles are grayish-brown to nearly black. They are about 1/8- to 1/4-inch long with a medium-sized beak projecting downward from the front of the head. The weevils overwinter as adults. In the spring the females lay eggs on the alfalfa stem. There are 3 to 4 larvae instars over a period of 29 to 58 days. The larvae become full grown about the first cutting and drop to the soil where they spin a cocoon and emerge as adults in 10 days. The adults can live for 10 to 14 months. There is one complete and sometimes a partial second generation per year.

Geographical Distribution: In all alfalfa-growing areas in West, midland & eastern United States.

Damage and Treatment: After feeding in the stems for 4 to 5 days, larvae emerge and feed in the terminal buds, severely stunting the crop.

Treatment should be made when insect populations and/or damage levels reach economic thresholds. Refer to local University Extension Pest Management Guidelines for specific state thresholds.