Parasitic wasp

Encarsia formosa

Adult females of this parasitic wasp are about mm long, with a dark brown head and thorax and a yellow abdomen. Males are rare in commercial strains_ This species will attack both the greenhouse whitefly (Trialeurodes vaporariorum) and the sweet potato whitefly (Bemisia tabaci).
The former is generally considered the better host for this species, but E. formosa can also be a useful complement to Eretmocerus eremicus for managing B. tabaci.

Both E. formosa and Eretmocerus eremicus kill whiteflies in two ways: through parasitism through ‘host-feeding’. In the latter case, the whitefly is pierced by the wasp’s ovipositor (egg-laying apparatus) and the wasp feeds on the fluids released from the wound; although no eggs are Iaid in these hosts, they are nevertheless killed by the host-feeding proces.

Encarsia formosa will accept all stages (except eggs) of both greenhouse whitefly and sweet potato whitefly for host-feeding, prefers older nymphs (3 rd and 4 th instar) for parasitism.
Parasitized greenhouse whiteflies eventually turn black and de as the wasp larva develops within; sweet potato whitefly parasitized by E. formosa typically turn a paler amber-brown.

Encarsia formosa is most effective in sunny/well-lit conditions and at temperatures of 20 to 28°C (68—82 °F). Activity is much reduced at daytime temperatures below 18°C (64°F) and by reduced light intensities_ At temperatures of 21—22°C (70—72 °F), the life-cycle (egg to adult) is completed in approximately 25 days_ When conditions are favorable, E. formosa can be very efficient at searching for whiteflies, making it a good choice for release at low whitefly densities.