Biology and use of the whitefly parasitoid Encarsia formosa.

Encarsia formosa is a parasitoid used worldwide for the biological control of whiteflies on vegetables and ornamental plants grown in greenhouses. Because of outstanding success in controlling Trialeurodes vaporariorum on tomatoes, the biology and behavior of this wasp have been intensively studied to identify attributes that contribute to successful biological control and how best to manipulate augmentative releases into greenhouses to suppress whitefly population growth. In this article, we review the biology of adult and immature E. formosa, population dynamics of whitefly-parasitoid interactions, and commercial use in greenhouses. Deficits in knowledge of aspects of E. formosa's biology and use are noted.

Field estimates of numbers of Ixodes scapularis (Acari:Ixodidae) larvae and nymphs per hectare successfully feeding on Peromyscus leucopus in Massachusetts.

The numbers of blacklegged tick, Ixodes scapularis Say, per hectare that engorged as larvae and nymphs on white-footed mice, Peromyscus leucopus (Rafinesque), were estimated at 3 sites in coastal Massachusetts. Estimates of numbers of engorged ticks dropping per day from trapped mice were multiplied by mark-recapture estimates of the density (numbers per hectare) of white-footed mice to estimate numbers of ticks engorging on mice per hectare. In 1991, estimates of seasonal totals per hectare of I. scapularis nymphs completing blood meals on P.leucopus ranged from 825 +/- 68 at Nonamesset to 6,654 +/- 770 at Menemsha. This absolute sampling method (the drop-off method) was compared with drag sampling for nymphal ticks. Per hectare estimation of engorgement rates overcomes a shortcoming associated with drag sampling because site-to-site comparisons can be made even where vegetation structure differs markedly among sites. The drop-off method may be used to quantify the contribution of any host to the engorged tick population, provided sufficient such hosts can be collected on a weekly basis.

Host acceptance and discrimination byComperia merceti (Compere) (Hymenoptera: Encyrtidae) and evidence for an optimal density range for resource utilization.

The cement used by females ofSupella longipala (F.) (Orthoptera∶Blattellidae) to bind their oothecae to substrates acts as a kairomone for host acceptance by the parasitoidComperia merceti. C. merceti discriminates parasitized from unparasitized oothecae and oviposts at reduced levels in the former. Low survival rates for parasitoids reared from oothecae receiving fewer than four ovipositions suggests that an "optimal density range" for resource utilization byC. merceti exists.