Matt Montgomery, Sangamon/Menard Extension unit educator in crop systems, has reported finding clover leaf weevils in some alfalfa fields in southern Sangamon County. Kevin Black, with Growmark, also has found clover leaf weevils in some fields of alfalfa and red clover. Although clover leaf weevils rarely cause economic damage in alfalfa in Illinois, their presence should be noted because they can be confused with alfalfa weevils.|
Although somewhat similar in appearance to both larvae and adults, clover leaf weevils and alfalfa weevils have distinctly different characteristics:
· The larvae of both species are green with a white stripe along the center of the back. However, the white stripe on the clover leaf weevil is bordered with smudges of pink or red.
· The head of a clover leaf weevil larva is tan; the head of an alfalfa weevil larva is dark brown.
· A fully grown clover leaf weevil larva is about 1/2 inch long; a fully grown alfalfa weevil larva is about 3/8 inch long.
· An adult clover leaf weevil (5/16 inch long) is about two times larger than an adult alfalfa weevil (3/16 inch long).
· An adult clover leaf weevil is light brown on the sides with a wide, dark brown stripe on the back. An adult alfalfa weevil is brown with a narrow dark stripe along the center of the wing covers.
Comparative photographs of these two species can be found in the April 27, 1997, issue of Iowa State University's Integrated Crop Management (http://www.ipm.iastate.edu/ipm/ icm/1997/4-21-1997/aflweevil97.html).
Clover leaf weevils and alfalfa weevils also feed and behave differently. Clover leaf weevil larvae feed at night, usually on lower leaves. They can be found on the ground around the crowns during the day. Alfalfa weevil larvae feed actively on alfalfa foliage, starting near the tips, during the day.
Don't confuse the two species. Including counts of clover leaf weevils with counts of alfalfa weevils could inflate the estimate of the alfalfa weevil population.--Kevin Steffey