Biological Control of Bemisia argentifolii (Homoptera: Aleyrodidae) on Poinsettia with Inundative Releases of Encarsia formosa Beltsville Strain (Hymenoptera: Aphelinidae): Can Parasitoid Reproduction Augment Inundative Releases?

Abstract

The effectiveness of inundative releases of the parasitoid Eucarsia formosa Beltsville strain for control of Bemisia argentifolii Bellows & Perring on poinsettia ( Euphorbia Pulcherrima Willd. ex Koltz.) was determined in replicated experimental greenhouses. We evaluated 2 release rates of E. formosa Beltsville strain: a low release rate (1 wasp per plant per week, released in 2 greenhouses) and a high release rate (3 wasps per plant per week, released in 2 greenhouses), over a 14-wk growing season. The trial had 1 control greenhouses in which B. argentifolii developed on poinsettia in the absence of E. formosa Beltsville strain. Life-tables were constructed for B. argentifolii in the presence and absence of E. formosa Beltsville strain by using a photographic technique to follow cohorts of whiteflies on poinsettia leaves. Weekly population counts of the whitefly were also made. In the absence of E. formosa Beltsville strain, egg to adult survivorship of B. argelltifolii on poinsettia was 71%. At the low release rate, egg to survivorship of B. argelltifolii was 4% and parasitism was 23%. At the high release rate, egg to adult survivorship for B. argentifolii was 1% and parasitism was 12%. The net reproductive rates (R) for B. argentifolii populations in the absence of E. formosa Betsville strain was 17.1, indicating a rapidly increasing population. Net reproductive rates for whitefly populations subject to wasp releases were 0.95 for the low release rate greenhouses. and 0.32 for the high release rate greenhouses. indicating declining B. argentifolii population growth. The high release rate provided better control of B. argentifolii than the low release rate and this was attributed to higher levels of in-house wasp reproduction. At time of harvest, the mean number of live nymphs and pupae per leaf in the high release rate greenhouses was not significantly different from numbers counted on leaves on plants being sold at commercial retail outlets.