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WEF5C - 500 Parasite Eggs on Hanging Cards
WEF1K - 1,000 Parasite Eggs on Hanging Cards
Encarsia formosa is a tiny parasitic wasp that parasitizes whiteflies. It was the first biological control agent developed for use in greenhouses. Adults are black with yellow abdomen, less than 1 mm (1/20 inch) long (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 used to control greenhouse whitefly on greenhouse cucumbers, tomatoes, peppers and poinsettias and other plants grown in greenhouses. They control silverleaf/sweet potato whitefly using high release rates. Optimum conditions are temperatures over 20°C (68°F) and relative humidity 50-70%. When daytime temperatures are less than 18°C (64°F). Encarsia activity is sharply reduced, making them less effective. Encarsia should not be used if high whitefly populations are already established.
The predatory beetle Delphastus avoids feeding on whiteflies parasitized by Encarsia, therefore it can be used with Encarsia. The parasitic wasp Eretmocerus californicus may also be used with Encarsia.
Check the undersides of lower leaves for parasitized whitefly scales. They turn black (for greenhouse whitefly) or transparent brown (for sweet potato whitefly) so are easy to tell from unparasitized scales, which are whitish.
The complete life cycle takes about 28 days at 21°C (70°F). Temperature affects developmental rate; for example, larval development takes 15 days at 25°C (77°F) and 45 days at 15°C (59°F). Encarsia populations are all female (males sometimes occur but they are not functional). Eggs are laid in 2-week-old whitefly scales (second and third whitefly larval stages), one egg per whitefly. Most Encarsia are female and each lays up 10 eggs per day for an average of 200 eggs. Larvae develop inside the whitefly scale for 10 days (at 20° - 25°C). They pupate for another 10 days, then adults emerge by chewing a hole in the top of the scale. Adults are most active for about 10 days, although they can live up to 30 days.
Encarsia pupae are sold glued onto 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 some cards must be placed on the baskets, as well as on infected plants.
Adults will emerge from the pupae over a period of 1-2 weeks at 20° -25°C.
Small emergence holes in the pupae are visible using a 5-10X lens and indicate that the parasite has emerged.
If necessary, the Encarsia pupae can be held for up to 2 weeks at 5°-10°C (40°-50°F), however the percentage of emergence will decrease with time.
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.
Spreader stickers in spray applications are harmful to Encarsia.
If whitefly hot spots develop, spot spray with Safer's soap (1% solution), weekly, directing the spray onto new leaves to kill adult whiteflies and early stages of scale. Kinoprene (Enstar) may also be used on ornamental crops.