Parasitism of Bemisia argentifolii on collard with reduced or normal leaf wax
Collard, Brassica oleracea var. acephala L., cultivars with reduced leaf wax (i.e., glossy phenotypes) possess ovipositional antixenotic resistance to the silverleaf whitefly, Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae). We investigated parasitism by 2 parasitoids of B. argentifolii reared on 2 phenotypes of the collard cultivar 'Green Glaze', differing in amount of leaf wax. When Eretmocerus sp. (Hymenoptera: Aphelinidae) parasitoids were given a choice between parasitizing whitefly nymphs on glossy and normal-wax collard, there were no significant differences in the number of parasitized nymphs on the 2 plant phenotypes. However, 4.5 times more Encarsia pergandiella Howard (Hymenoptera: Aphelinidae) emerged from whiteflies on glossy than on normal-wax plants. In a no-choice test, the number of Eretmocerus sp. emerging on glossy and normal-wax plants did not differ significantly. In a similar no-choice test, more than twice as many E. pergandiella emerged from whiteflies on glossy collard than on normal-wax collard. Time to 50% emergence for whiteflies and both species of parasitoids did not differ on the 2 collard types in any of the no-choice tests. We conclude that management of B. argentifolii populations can be improved on collard, and probably other B. oleracea vegetables, through the use of reduced leaf wax cultivars that have antixenotic resistance to B. argentifolii and have no detrimental effects, possibly even beneficial effects, on important whitefly natural enemies.