Evaluation of inundative releases of Eretmocerus eremicus and Encarsia formosa Beltsville strain in commercial greenhouses for control of Bemisia argentifolii (Hemiptera : Aleyrodidae) on poinsettia stock plants

The effectiveness of weekly inundative releases of 3 female Eretmocerus ere micus (evaluated in 2 greenhouses) and 4-7 Encarsia formosa Beltsville stra in (evaluated in 2 greenhouses) per plant for control of Bemisia argentifol ii Bellows & Perring [ =Bemisia tabaci (Gennadius) strain B (Bellows et al. 1994)] (Homoptera: Aleyrodidae) on poinsettia stock plants was determined under commercial growing conditions. We constructed partial life-tables for B. argentifolii in the presence and absence of parasitoids in each of 4 gr eenhouses to quantify parasitoid impact. Weekly population counts of B, arg entifolii were also made. Initial starting densities of live B. argentifoli i nymphs and pupae on cuttings used for the stock plant crop ranged from 0. 25 to 1.86. Each site where each parasitoid species was tested had 1 relati vely low and high initial starting density of B. argentifolii. Under these conditions, E. eremicus effectively controlled B. argentifolii at 2 sites a nd cuttings were harvested with 0.656-1.49 live nymphs and pupae per leaf w ithout insecticide use. Trials with E. formosa Beltsville strain were termi nated early at 2 sites and insecticides were applied before the harvesting of cuttings because this parasitoid failed to control B, argentifolii altho ugh initial starting densities of B. argentifolii were similar to those in E. eremicus greenhouses. The cost of using E. eremicus was compared with th e cost of the insecticide imidacloprid for B. argentifolii control at 1 sit e. At a retail cost of $22 per 1,000 parasitoids in 1995, the use of E. ere micus was 44 times more expensive than imidacloprid.