Encarsia formosa is a tiny parasitic wasp that parasitizes whiteflies. It was the first biological control agent developed for use in greenhouses. The whitefly species in a crop must be correctly identified to make sure it is a species that Encarsia can control and to determine the correct release rate.
Encarsia are effective controls for greenhouse whitefly on greenhouse cucumbers, tomatoes, peppers and poinsettias. They can control silverleaf/sweet potato whitefly, but only under optimum management using high release rates.
The predatory beetle Delphastus catalinae avoids feeding on the whiteflies that have been parasitized by Encarsia. Delphastus adults also feed on whitefly eggs and can therefore be used with Encarsia. The predatory bug Dicyphus hesperus may be used with Encarsia. The parasitic wasp Eretmocerus californicus may also be used with Encarsia.
Best use preventatively at roughly 0.1 per square foot before adult whiteflies are seen and 0.2 per square foot thereafter. Monitor on the lower leaves and look for black scales. When 90% present are black, reduce rate.
Optimum conditions are temperatures over 68°F (20°C), high light levels (7300 lux) and relative humidity 50-70%. When daytime temperatures are less than 64°F (18°C) Encarsia activity is sharply reduced, making them less effective. Do not attempt to use Encarsia if high whitefly populations are already established
Encarsia pupae are sold glued onto cards or as loose scales. For pupae on cards, it is important to hang the cards from lower leaves in the shade as Encarsia tend to fly upward. Avoid wetting them while watering. If there are hanging baskets in the greenhouses, some cards must be placed on the baskets, as well as on plants on benches. Do not attempt to use Encarsia if high whitefly populations are already established.