Biology of Cosmobaris amertcana Casey1, a Weevil Attacking Sugarbeets2

Abstract

Adult and larval feeding on the petioles of sugarbeets, Beta vulgaris L., by Cosmobaris americana Casey, a weevil that attacks betaceous crops and several weeds, chiefly members of Amaranthaceae and Compositae, interfered with the translocation processes; larval feeding also caused injured petioles to wither and die. In the Northwest, adults first appeared in May and lived 3-4 months; eggs were first deposited in feeding pits in late May, and eggs started hatching in June. The larvae developed slowly, but became full grown in August; those that were not full grown by October died during the winter. Full-grown larvae overwintered in old feeding galleries in weed hosts and only rarely in sugarbeets; pupae and adults were both produced mostly in May. There was 1 generation. The suitability of various plants for completion of the weevil's life cycle depended largely on the moisture in the parenchymous tissues mined by the larvae. Larvae feeding in watery petioles of sugarbeets drowned in decomposing tissues or starved after the injured part dried and died; larvae feeding in woody stems of weeds were not so affected.