Evaluation of Eretmocerus eremicus and Encarsia formosa (Hymenoptera: Aphelinidae) Beltsville Strain in Commercial Greenhouses for Biological Control of Bemisia argentifolii (Homoptera: Aleyrodidae) on Colored Poinsettia Plants
The effectiveness of average weekly inundative releases of female Eretmocerus eremicus (evaluated in 2 greenhouses) and Encarsia formosa Beltsville strain (evaluated in 2 greenhouses) per plant for control of Bemisia argentifolii Bellow and Perring was determined on colored poinsettia plants grown under commercial conditions. Parasitoid efficacy was determined by making weekly population counts of B. argentifolii lifestages (excluding eggs) on plants exposed to parasitoids in biological control greenhouses and comparing final per leaf densities of B. argentifolii nymphs to those plants in insecticide treated greenhouses. At the 2 sites where E. eremicus was used, final nymphal densities ranged from 2-4 per leaf when a sales inspection protocol was employed at time of harvest. On insecticide-treated plants, nymphs ranged 0.02-0.18 per leaf but final whitefly densities in biological control greenhouses and insecticide greenhouses were commercially acceptable. Colored 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 were harvested without further use of insecticides. In comparison to insecticides, the cost of E. 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 terminated early and insecticides were applied when B. argentifolii densities reached 4-6 live nymphs and pupae per leaf. Low emergence rates of E. formosa Beltsville strain may have been a major factor lowering the efficacy of this parasitoid in commercial greenhouses.