BIOLOGICAL-CONTROL OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) INFESTING EUPHORBIA-PULCHERRIMA - EVALUATIONS OF RELEASES OF ENCARSIA-LUTEOLA (HYMENOPTERA, APHELINIDAE) AND DELPHASTUS-PUSILLUS (COLEOPTERA,COCCINELLIDAE)
Km. Heinz et Mp. Parrella, BIOLOGICAL-CONTROL OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) INFESTING EUPHORBIA-PULCHERRIMA - EVALUATIONS OF RELEASES OF ENCARSIA-LUTEOLA (HYMENOPTERA, APHELINIDAE) AND DELPHASTUS-PUSILLUS (COLEOPTERA,COCCINELLIDAE), Environmental entomology, 23(5), 1994, pp. 1346-1353
Releases of Encarsia luteola Howard and Delphastus pusillus LeConte we
re evaluated for their ability to control Bemisia argentifolii Bellows
& Perring, n. sp. greenhouse-grown poinsettias. Three treatments, eac
h replicated three times, were used to assess the impact of natural en
emy releases on B. argentifolii populations: (1) a complete exclusion
of natural enemies cage, (2) an identical exclusion cage receiving nat
ural enemy releases as a control for cage effects, and (3) releases of
natural enemies onto plants within the greenhouse but outside of eith
er cage. Weekly releases of the parasitoid E. luteola were initiated t
he week the plants entered the greenhouse and three releases of D. pus
illus, 1 wk apart, were made when B. argentifolii populations rose dra
matically 9 wk into the trial. Release rates for both natural enemies
were one insect per plant per week. Weekly collected leaf samples were
examined with the aid of a dissecting microscope. The numbers of live
whiteflies were recoded by developmental stage as were the numbers of
dead (resulting from natural causes, D. pusillus predation, or E. lut
eola host-feeding) and parasitized whitefly nymphs. The lack of a sign
ificant difference in whitefly densities between the two natural enemy
release treatments suggested the absence of a cage effect on whitefly
populations. Whitefly densities within the complete exclosure cages w
ere significantly greater than the whitefly densities in either of the
two natural enemy release treatments, indicating a significant impact
of natural enemy releases on B. argentifolii infestations. Whitefly d
amage to harvested plants within the natural enemy release areas was n
ot significantly different from the damage level observed in the growe
r-treated area. The direct cost associated with B. argentifolii biolog
ical control ($166.32 per greenhouse section) was almost-equal-to 5 ti
mes greater than the insecticide-based B. argentifolii management prog
ram currently used by poinsettia growers. This cost differential can b
e reduced if the indirect environmental and worker-safety costs associ
ated with insecticide use are included, and further reductions should
accompany increased commercial availability of D. pusillus.