Alfalfa leafcutting bee-Eulophid Wasp

Melittobia acasta

Pest description These small, dark brown wasps (adults 1 to 1.5 mm) are ectoparasitoid idiobionts that develop gregariously. Female adults chew through cocoons and repeatedly insert ovipositor where she then feeds on the hemolymph from the wound, and lays eggs. Eggs are initially laid on the ventral side of the host in batches of 4 to 12, and take from 15 to 28 days to develop through four instars. Several hundred progeny may be produced over multiple successive generations each year. Females prefer to oviposit when the BOB are in pre-pupa or pupa stages, and are attracted to cocoon volatiles, frass and acetic acid.

Management Use of traps when rearing alfalfa leafcutting bees is recommended from May to November to attract and control parasites that emerge from nests returning from the field. Plastic strips coated with Dichlorvos is an effective trap in climate-controlled rooms. Parasites directly exposed to strip die within 2 hours, or 7 to 8 hr if buffered by a cocoon. The strips should be used as soon as the first parasites emerge, but with great care as to not expose the bee for a prolonged amount of time. No predators upon Melittobia have been recorded.

For more information:

De Wael, L., M. De Greef and O. Van Laere.1995. Biology and control of Melittobia acasta. Bee World, 76(2): 72-76.