Oklahoma State University Stillwater, OK
Oklahoma Alfalfa Oklahoma Cooperative Extension Service Oklahoma Agricultural Experiment Station

Alfalfa Seed Chalcid
Life Cycle and Damage. The adult of this species is a tiny, black wasp; length = 1/10 inch) that lays eggs in developing alfalfa seeds within green pods. A single larva develops within each seed, destroying all contents, then forms a pupal stage. Upon emergence from the pupal stage, adults chew holes in seeds and seed pods to escape and lay eggs for a new generation. Several generations are completed each year, with increasing population densities and greater potential for damage through mid- and late summer. Larval and pupal stages of the fall generation overwinter in seed to emerge as adults the following spring. Surveys of damage in seed produced in Oklahoma have shown up to 80% loss due to the seed chalcid, with an average loss of 10-15%. Sampling and Control. Seed chalcids cannot be controlled effectively with chemical insecticides and spray applications made during bloom and seed set may cause high levels of mortality to pollinators. Thus, the primary means for limiting infestations is reduction of populations entering seed production fields through sanitation. Methods of sanitation include: Elimination of volunteer alfalfa along fence rows and roadsides by mowing or spraying with herbicides. The primary source of host plants for the chalcid in spring and early summer is volunteer alfalfa. Careful harvesting to avoid spilled seed that can serve as overwintering sites for chalcids. Not storing uncleaned seed through the winter as it may be infested with chalcids. Schedule seed production to complete harvesting by mid-August to avoid the time in late summer when the highest populations of chalcids are present. Additional information on alfalfa seed chalcids can be found at Oklahoma Alfalfa.
Richard Berberet, Alfalfa Entomologist  Department of Entomology and Plant Pathology  Oklahoma State University

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