Encarsia (Pronounced: EN-CAR-SEE-A)is a tiny black and yellow parasitic wasp about 1mm in length. Adult females lay their eggs into whitefly scales (the static, sap-sucking whitefly larvae).
Encarsia Life Cycle
An adult female will lay up to 60 eggs during her short lifetime of 10 to 14 days. Whitefly scales that have been parasitised by Encarsia turn black after about 10 days. Development from egg to adult takes about 28 days at 20°C or 14 days at 30°C.
They should only be used in greenhouses or conservatories.
Encarsia should be introduced at the first sign of whitefly, yellow sticky traps can be used to monitor when this is.
If temperatures are not high enough, use SB Plant Invigorator to keep the numbers down before Encarsia can be introduced.
If the whitefly population is already high, it is necessary to spray first with SB Plant Invigorator to reduce the numbers. It may also be necessary to repeat SB Plant Invigorator sprays after they are introduced, to help establish control at low whitefly levels. In this case, apply SB Plant Invigorator only to leaves that are densely infested with scales or adults. Generally, scales will be found on slightly older leaves and adults on young leaves towards the growing point of shoots. Spray undersides of leaves, where most of the whitefly are located.
They cannot be stored, and should be used on the day of receipt.
Temperatures should not fall below 10°C (50°F) at night, Encarsia will be most effective when temperatures are at least 18°C (64°F) during the day.
They may not work well on daturas or regal pelargoniums.
Encarsia are harmless to children, pets and wildlife and will not become a pest in its own right.
Adult whiteflies as their name suggests are white in colour. They resemble tiny moths and are about 3mm long. When they are not flying (which they do profusely when disturbed) they can usually be found on the undersides of leaves.
Young whitefly look like clear scales and can also be found on the undersides of leaves.
NB. Aphid cast skins are sometimes mistaken for whitefly! However, whitefly will fly away when disturbed, these cast skins will fall off or not move. Just shake the plant to find out which you have!
The whitefly eggs are laid in a horseshoe shape on the undersides of leaves. Once hatched the young nymphs move a short distance so that they are equally spaced and then moult into legless scales that spend the rest of their development feeding by sucking sap. These scales excrete a sticky “honeydew” which falls onto the leaves and fruit below.
Sooty moulds often develop on this “honeydew” and plants under attack appear to lack vigour.
Sooty moulds can reduce the amount of light reaching the leaves which can lead to leaf yellowing and plant death.
Whitefly Life Cycle
Whitefly go through several growing stages between egg and adult. The whole cycle takes about 30 days at 20ºC (68ºF). The length of the adults life depends on the plant on which it was raised.
Freshly hatched adults from the lower leaves of plants fly up to the younger leaves of the plant to lay their eggs.
Whitefly can over-winter in a greenhouse on crops or weeds and the scales can withstand the odd frost.
Biological Control of Whitefly
During the warmer months whitefly can be controlled biologically in greenhouses or conservatories by using their natural enemies such as Encarsia formosa or other specialist whitefly parasites and predators.