BIOLOGICAL-CONTROL OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) ON POINSETTIA WITH INUNDATIVE RELEASES OF ENCARSIA-FORMOSA BELTSVILLE STRAIN (HYMENOPTERA, APHELINIDAE) - CAN PARASITOID REPRODUCTION AUGMENTINUNDATIVE RELEASES

The effectiveness of inundative releases of the parasitoid Encarsia fo rmosa Beltsville strain for control of Bemisia argentifolii Bellows & Perring on poinsettia (Euphorbia pulcherrima Willd. ex Koltz.) was det ermined 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 gr owing season, The trial had 1 control greenhouse in which B. argentifo lii developed on poinsettia in the absence of E. formosa Beltsville st rain. Life-tables were constructed for B. argentifolii in the presence and absence of E. formosa Beltsville strain by using a photographic t echnique 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. argentifol ii on poinsettia was 71%. At the low release rate. egg to survivorship of B. argentifolii was 4% and parasitism was 23%. At the high release rate, egg to adult survivorship for B. argentifolii was 1% and parasi tism was 12%. The net reproductive rates (R-o) for B. argentifolii pop ulations in the absence of E. formosa Beltsville strain was 17.1, indi cating a rapidly increasing population, Net reproductive rates for whi tefly populations subject to wasp releases were 0.95 for the low relea se rate greenhouses, and 0.32 for the high release rate greenhouses, i ndicating declining B. argentifolii population growth. The high releas e rate provided better control of B. argentifolii than the low release rate and this was attributed to higher levels of in-house wasp reprod uction. At time of harvest, the mean number of live nymphs and pupae p er leaf in the high release rate greenhouses was not significantly dif ferent from numbers counted on leaves on plants being sold at commerci al retail outlets.