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Biological Controls for serious gardeners
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Encarsia formosa

This insect is one of the most famous examples of biological controls. Encarsia formosa is dependent on the whitefly to lay its eggs, and for food, killing it in the process. It parasitizes 16 different species of whitefly in different parts of the world and each adult can kill around 100 whitefly nymphs in its lifetime. Encarsia formosa is often described as a "parasitic wasp" but althogh related to the wasp it is much much smaller, and it does not sting humans, it "stings" whitefly larvae. It is so effective that it is now the professional growers choice for controlling whitefly in glasshouses.


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Encarsia Cards

Encarsia is supplied as unhatched "pupae" or "scales" which are stuck onto a card, so that they can be conveniently hung around among your plants. The pupae will hatch out at intervals over the following week and the tiny insects then fly through the crop searching for whitefly larvae. The encarsia females lay eggs actually within the larvae, and when the egg hatches it consumes the whitefly from within. Initially it feeds without killing its host, so that the whitefly continues to feed and grow, but as the host larva reaches maturity and ceases to feed, the parasite attacks the vital organs. At this point the whitefly scale turns black, and about eight days later a new Encarsia emerges to repeat the process.

There are some special circumstances in which encarsia are not so successful and it is necessary to use a different predator. One is where the whitefly is not the common glasshouse whitefly (Trialeurodes vaporariorum) but the Tobacco Whitefly (Bemisia) The other is where the summer temperatures are particularily high in the day. In these cases there is another more expensive parasite called "eretmocerus" similar to encarsia which should be used as well. Click here for information about whitefly Click here for information about eretmocerus

Encarsia works best with temperatures above 21C with 12hr+ daylight hours. Generally, this means introducing Encarsia from mid April to August, although it can be earlier or later with extra heat and light. They will stay with their prey within a greenhouse, but are not suitable for applying outdoors

Encarsia formosa cards

The Standard pack (5 cards) should give good control for an average conservatory or small greenhouse. If you have a longstanding battle with whitefly order two packs with separate delivery dates. Then you can follow up the initial treatment with a second introduction two weeks later.
The Larger pack should be used if the Whitefly infestation is very bad or the area large. .
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Pack of 5 cards
7.95 inc P&P

Pack of 20 cards
17.95 inc P&P