Encarsia formosa

Target Pests: Greenhouse whitefly (Trialeurodes vaporariorum), silverleaf whitefly (Bemesia argentifolia), sweet potato whitely (Bemesia tabaci)

Description: “Encarsia” is a tiny parasitic wasp that parasitizes whiteflies. It was the first biological control agent developed for use in greenhouses. Adults are black with a yellow abdomen, less than 1 mm long. Even though they are wasps, they do not sting. Larval stages live entirely inside immature whiteflies, which darken and turn black as the parasites develop inside.

Use as Biological Control: Encarsia are effective controls for greenhouse whitefly on greenhouse cucumbers, tomatoes, peppers and poinsettias. They can control silverleaf and sweet potato whitefly, but only under optimum management using high release rates.

Optimum conditions are temperatures over 61°F (20°C), high light levels (7300 lux), and relative humidity 50-70%. When daytime temperatures are less than 64°F, Encarsia activity is sharply reduced, making them less effective.

Do not attempt to use Encarsia if high whitefly populations are already established. The predatory ladybug Delphastus avoids feeding on the whiteflies that have been parasitized by Encarsia and also feed on whitefly eggs, therefore can be used in conjunction with Encarsia. The predatory bug Dicyphus hesperus and the parasitic wasp Eretmocerus californicus may also be used in conjunction with Encarsia.

Life Cycle: The complete life cycle takes about 28 days at 70°F (21°C). Temperature greatly affects development rate; larval development takes 15 days at 77°F and 45 days 59°F. Encarsia populations are all female. Sometimes males do occur, but they are not functional.

Eggs are laid in 2-week old whitefly scales (2^nd and 3^rd whitefly stages), one egg per whitefly. Each female lays up to 10 eggs per day, for a lifetime average of 200 eggs.

Larvae develop inside the whitefly scale for about 10 days at around 70°F. They then pupate for another 10 days, when adults emerge by chewing a hole in the top of the scale. Adults are most active for about 10 days, but can live up to 30 days. In addition to parasitizing them, Encarsia kill whitefly scales by feeding on the host directly. They also feed on whitefly honeydew.

For Best Results: The whitefly species in a crop must be correctly identified to make sure it is a species that Encarsia can control, which will also help determine appropriate release rates. Eliminate whitefly from alternate plant sources, such as weeds, previous crops, and/or cuttings before Encarsia releases begin. High whitefly populations hinder movement of the parasite as does the presence of excessive amount of honeydew. Remove whiteflies and honeydew by spraying with water or insecticidal soap.

Using Pesticides: Encarsia are extremely sensitive to insecticide residues. Plastic covering or flooring used in greenhouses may harbor residues at levels that are harmful to this parasite for over 6 months. If, after a month of introducing Encarsia, whitefly parasitism is not occurring, contact supplier for assistance. Commercial spreader stickers in spray applications are harmful to Encarsia.