University of Illinois

No. 7/May 9, 1997

Alfalfa Weevil Update

The headline story with alfalfa weevils continues to be the cool weather. Development of alfalfa weevils has been quite slow, as indicated by comparing maps of actual and predicted heat-unit accumulations in previous issues of this Bulletin. If you are continuing to track the biological activity of alfalfa weevils throughout the state, Figure 2 shows the actual heat-unit accumulation (base 48 degrees F) from January 1 to May 4, 1997. Predicted heat-unit accumulation from January 1 to May 18 is shown in Figure 3.

Figure 2. Actual heat-unit accumulation (base 48 degrees F) from January1 to May 4, 1997.Figure 3. Projected heat-unit accumulation (base 48 degrees F) from January1 to May 18, 1997.

Jim Morrison, Crop Systems educator in Freeport, and David Feltes, IPM educator in the Quad Cities, were working in an alfalfa field in Ogle County on May 6 and found no alfalfa weevils. Given the accumulated heat units as of May 5, this is not surprising because weevil eggs usually do not hatch until about 200 heat units above 48 degrees F have accumulated. However, they did find a potato leafhopper. Leafhoppers before alfalfa weevils--what is the world coming to?

We still have not received reports of any significant damage caused by alfalfa weevils. This may not be their year. If you become aware of weevil problems in alfalfa in your area, don't hesitate to contact us.

Kevin Steffey, Extension Entomology, (217)333-6652