Evaluation of Eretmocerus eremicus and Encarsia formosa (Hymenoptera : Aphelinidae) Beltsville strain in commercial greenhouses for biological control of Bemsia argentifolia (Homoptera : Aleyrodidae) on colored poinsettia plants

The effectiveness of average weekly inundative releases of female Eretmocer us eremicus (evaluated in 2 greenhouses) and Encarsia formosa Beltsville st rain (evaluated in 2 greenhouses) per plant for control of Bemisia argentif olii Bellow and Perring was determined on colored poinsettia plants grown u nder commercial conditions. Parasitoid efficacy was determined by making we ekly population counts of B. argentifolii lifestages (excluding eggs) on pl ants exposed to parasitoids in biological control greenhouses and comparing final per leaf densities of B. argentifolii nymphs to those plants in inse cticide treated greenhouses. At the 2 sites where B, eremicus was used, fin al nymphal densities ranged from 2-4 per leaf when a sales inspection proto col was employed at time of harvest. On insecticide-treated plants, nymphs ranged 0.02-0.18 per leaf but final whitefly densities in biological contro l greenhouses and insecticide greenhouses were commercially acceptable. Col ored plants at one site where E. eremicus was used were harvested and sold without any insecticide use. At the second E. eremicus site, two sulfotepp applications were made at week 11 of the 16 week trial and colored plants w ere harvested without further use of insecticides. In comparison to insecti cides, the cost off. eremicus in 1995 ($2.70 per plant) was 30 times higher than using imidacloprid ($0.09 per plant) for B. argentifolii control. At the 2 sites where E. formosa Beltsville strain was released, trials were te rminated early and insecticides were applied when B. argentifolii densities reached 4-6 live nymphs and pupae per leaf. Low emergence rates of E. form osa Beltsville strain may have been a major factor lowering the efficacy of this parasitoid in commercial greenhouses.