POINSETTIA (EUPHORBIA-PULCHERRIMA WILLD EX KOLTZ) CULTIVAR-MEDIATED DIFFERENCES IN PERFORMANCE OF 5 NATURAL ENEMIES OF BEMISIA-ARGENTIFOLII BELLOWS AND PERRING, N-SP (HOMOPTERA, ALEYRODIDAE)

Laboratory evaluations of five natural enemies of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring, n. sp., were conducted to determine their potential as biological control agents in greenhouse poinsettia ranges. Adult longevity, prey consumption or host feeding and parasitism rates, and parasitoid emergence were measured for one predator, Delphastus pusillus LeConte, and four parasitoids, Encarsia formosa Gahan, Encarsia luteola Howard, Encarsia pergandiella Howard, and Encarsia transvena (Timberlake), as possible indicators of efficacy. Characterization of each parameter was performed on two poinsettia cultivars: the first, 'Annette Hegg Brilliant Diamond,' has trichome densities on the leaf undersurfaces approximately 15% less than the trichome densities on the leaf undersurfaces of the second cultivar, 'Lilo.' Adult longevity varied significantly between natural enemies (ranging from an average high of 85.2 days for female D. pusillus feeding on B. argentifolii nymphs to an average low of 2.8 days for the Canada colony of E. formosa), but not between cultivar. Prey consumption and oviposition by D. pusillus varied between prey type (nymphs consumed > eggs consumed) and poinsettia cultivar ('Annette Hegg Brilliant Diamond' > 'Lilo'). Host feeding, parasitism and total number of B. argentifolii nymphs killed varied significantly among Encarsia spp., but no single wasp performed better than the rest across all three parameters. Host feeding, parasitism, and total number of nymphs killed were greater on 'Annette Hegg Brilliant Diamond' than on 'Lilo' and this difference was consistent among the four parasitoid species. Among parasitoid species differences in percentage emergence were consistent between the two poinsettia cultivars with emergence from parasitized nymphs on 'Lilo' being greater than emergence on 'Annette Hegg Brilliant Diamond.' Results from these evaluations suggest that the probability of achieving successful augmentative biological central will be greater on poinsettia cultivars with fewer trichomes. In addition, achieving biological control is likely to be difficult with releases of E. transvena, but a greater chance for success may be possible through releases of D. pusillus when whitefly densities are high or through releases of E. formosa (Beltsville colony) or mated E. pergandiella independent of whitefly densities. (C) 1994 Academic Press, Inc.