Seed wasp on multiflora rose, Rosa multiflora, in Virginia.
R. multiflora is a major weed of pastures, highway embankments and recreational areas. A chalcid wasp, Megastigmus aculeatus, which feeds on R. multiflora seeds, is a potential biological control agent. Examination of R. multiflora achenes collected from 58 sites in 51 counties in Virginia during 1983-86 showed that M. aculeatus was present in all but one of the counties. Female:male ratio was high (94:1) indicating parthenogenesis. Infestation rates of the achenes averaged 26.5% in 1985 and 23.9% in 1986. Severe winter temp. appears to affect the wasp population adversely.