EVALUATION OF ENCARSIA-FORMOSA (HYMENOPTERA, APHELINIDAE) TO CONTROL BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) ON POINSETTIA (EUPHORBIA-PULCHERRIMA) - A LIFETABLE ANALYSIS

Weekly releases of the parasitoid Encarsia formosa Gahan failed to con trol a low density population (initially, 0.51 nymphs and pupae per pl ant) of the whitefly Bemisia argentifolii Bellows & Perring on greenho use grown poinsettia plants in Massachusetts when released at the rate of 4-7 adult females per plant. A lifetable constructed for uncaged B . argentifolii in the presence of E. formosa indicated that survivorsh ip from the first/second instar to adult emergence was 14%. In contras t, in a lifetable constructed for B. argentifolii on caged poinsettia from which E. formosa was excluded, survivorship was 67%. Release of E . formosa reduced the number of insecticide applications on poinsettia by 75%, but the cost of using E. formosa (on a per m(2) basis) was 9. 5 times that of insecticides alone.