No. 8 Article 7/May 14, 2004

Where Are the Alfalfa Weevils?

Has the alfalfa weevil come and gone? We've heard very little concerning this pest over the past 2 weeks. In their latest "Tips for Crop Watchers," Jim Morrison, crop systems educator in Rockford, and Dave Feltes, IPM Extension educator, Quad Cities, report light weevil activity and small pinhole feeding in fields in northwestern Illinois. Degree-day accumulations since January 1 (base 48°F) indicate that producers in the northern half of Illinois may be finding alfalfa larvae in their fields (Figure 1). Growers should scout alfalfa fields for pinhole feeding and larvae feeding on leaf tips. Also keep alert for brown or discolored larvae. These larvae may have been infested with a fungus called Zoophthora phytonomi. This fungus is favored by a warm and humid environment. Dave and Jim remind growers to scout fields to avoid any surprises and keep postharvest intervals in mind if insecticide treatments are needed.--Kelly Cook

Figure 1. Degree-day accumulations (base 48°F) from January 1 through May 12.

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