Blue orchard bee-Eulophid wasp

Melittobia acasta

Pest description These small, dark brown wasps (adults 1-1.5 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 Plastic strips coated with Dichlorvos is an effective trap in climate-controlled rooms, and are most effective when used from May-November. Parasites directly exposed to strip die within 2 hours, or 7 to 8 hours 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 of 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.