Parasitic Wasp

Eretmocerus eremicus

Adult females of this species are approximately 0.7 mm long, with a lemon-yellow head and body; males are slightly smaller and somewhat darker in colour. Both sexes have green compound eyes and three red simple eyes (ocelli) at the top of the head.

Like Encarsia formosa, this species will also attack both the greenhouse whitefly (T. vaporariorum) and the sweet potato whitefly (B. tabaci), but the latter is generally considered to be the better host for this species. Eretmocerus eremicus will use all immature whitefly stages (except eggs) for host-feeding, but prefers the 2nd and 3 rd  instar nymphs for egg-laying. Rather than inserting its eggs inside the host, this species lays its eggs between the whitefly nymph and the leaf surface. On hatching, the wasp larva chews through the underside of the host and begins to feed, eventually completing its development inside the pupal stage of the host. The ‘mummified’ body of the dead whitefly host is yellowish-beige in colour (somewhat darker than unparasitized host stages). When the adult wasp is fully formed and ready to emerge, it chews an exit hole through the dead
host through which it crawls out.

Daytime temperatures for E. eremicus should be at least 21°C (70°F) with the optimal range being approximately 25—30°C (77—86°F). Eretrmocerus eremicus can maintain active host searching at temperatures slightly higher than 30°C, and generally tolerates higher temperatures better than does E. formosa. At 21°C (70°F), the life-cycle is completed in approximately 23 days.

In comparing Encarsia formosa and Eretmocerus eremicus, keep in mind the target whitefly species and the prevailing environmental conditions.  In many situations, the two species can be complementary.