When fully grown, the larvae spin a cocoon on the leaves of alfalfa plants or on the ground. A second generation of adult weevils emerges around mid-June, feeds for a few weeks but does not produce a second larval generation. Damage Larvae feed on the tips of plants and on leaves, resulting in a skeletonized plant. This insect is primarily a pest of the first cutting. However, if high populations were present just before the first cutting, regrowth of the second cutting may also be damaged.
Adults can also feed, but their damage is minor.
Larval damage results in reduced yield and quality of the first cutting. It may also result in season-long yield loss and reduce the life of the stand. If alfalfa is less than 12 inches tall when the weevil population peaks, fewer than 2 larvae per stem can defoliate a crop. In comparison, alfalfa greater than 18 inches tall can tolerate significantly higher populations. If fields are monitored routinely and sprayed only when economic levels are present, natural enemies may be able to suppress weevil populations below an economic level.