APHID HOST EFFECTS ON THE BIOLOGY OF DIAERETIELLA-RAPAE (HYMENOPTERA,APHIDIIDAE)

Mated female Diaeretiella rapae M'Intosh, maintained in the laboratory on Brevicoryne brassicae (L.), feeding on Brassica oleracea L. for 12 generations parasitized 8 of 14 aphid species to which they were expo sed for 24 h on caged host plants. Diaeretiella rapae parasitized four small gram (barley) feeding, two crucifer feeding, one cotton feeding , and one sunflower feeding aphid species. The total time required for immature development, the proportion of aphids parasitized, and the d ry weight of newly eclosed adults differed significantly among host sp ecies. A greater percentage of B. brassicae than of other species were parasitized (94%), and the dry weight of adults eclosing from B. bras sicae was greater than for other species. Results are discussed in ter ms of the potential utility of habitat diversification for improving b iological control of small grain aphid pests in the Southern Great Pla ins.