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

Abstract

The effectiveness of weekly inundative releases of 3 female Eretmocerus eremicus (evaluated in 2 greenhouses) and 4-7 Encarsia formosa Beltsville strain (evaluated in 2 greenhouses) per plant for control of Bemisia argentifolii Bellows and 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 greenhouses to quantify parasitoid impact. Weekly population counts of B. argentifolii were also made. Initial starting densities of live B. argentifolii 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 i relatively low and high initial starting density of B. argentifolii. Under these conditions, E. eremicus effectively controlled B. argentifolii at 2 sites and cuttings were harvested with 0.66-1.49 live nymphs and pupae per leaf without insecticide use. Trials with E. formosa Beltsville strain were terminated early at 2 sites and insecticides were applied before the harvesting of cuttings because this parasitoid failed to control B. argentifolii although initial starting densities of B. argentifolii were similar to those in E. eremicus greenhouses. The cost of using E. eremicus was compared with the cost of the insecticide imidacloprid for B. argentifolii control at 1 site. At a retail cost of $22 per 1,000 parasitoids in 1995, the use of E. eremicus was 44 times more expensive than imidacloprid.