In early April, the female weevils begin to chew holes in alfalfa stems with their beaks. They deposit one to 40 eggs in each cavity. The eggs are small and bright yellow, although they darken as they near maturity. Egg hatch occurs in one to two weeks. Later, they feed on the leaves, producing a characteristic ragged or skeletonized appearance.
Severe damage gives the field a grayish or whitish cast, as if it had been frosted.
Larvae usually can be found in the field for one to two months, mostly during May and June. Mature larvae move down the plant or drop to the ground and spin a fragile, lacelike cocoon attached to debris or the plant. A new adult emerges after 10 to 12 days. Adults can be found in the field until early fall, when they move to their overwintering sites. Any crop management practice that helps produce a dense, uniform stand will make the crop better able to tolerate insect feeding.