Encarsia formosa, specifically the greenhouse whitefly parasite, is a well-tested solution for the prevention and low-infestation management of greenhouse whiteflies. These 0.7mm mini-wasps are best used for preventing the establishment of the greenhouse whitefly (Trialeurodes vaporariorum). They can also tackle minor to medium infestations. And, if established, they can adequately protect a crop throughout the season. In addition to the greenhouse whitefly, Encarsia formosa can parasitize a few other whitefly species, the sweet potato whitefly (Bemisia tabaci), for example. Acceptable prevention and control of other whitefly species, however, is effectively unobtainable with Encarsia formosa and we do not recommend their use for this purpose. (For those species, use Eretmocerus eremicus)
Encarsia formosa are supplied as pupae protected in the greenhouse whitefly scales (pupae) which they had used as a host, and actually still are. These parasitized scales are adhered to a small card which can be hung in the plants.