Whitefly - plant pest

Signs - Most commonly found on houseplants and in greenhouses, when disturbing the leaves, the tiny white flies that hide under the leaves will fly up. May be found on vegetable crops outdoors in warm weather.

Damage - Sap suckers, will weaken the plant and make it susceptible to further attacks of pests and disease. They can have a surprising effect for such a small fly.

Treatment:

    Tap the leaves and, as a cloud of flies up, suck them up with a small battery vacuum cleaner - take care! or you'll damage the leaves.

    Avoiding whitefly on tomatoes without the use of chemicals.  Plant French Marigolds (Tagetes) between your tomato plants to keep whitefly away. It's not that the whitefly particularly don't like these marigolds, it's because the pungent smell from the marigolds masks the smell of the tomatoes that usually attract the whitefly.

    Whiteflies are attracted to yellow paper, hanging strips of sticky yellow paper will catch the whitefly, these are available commercially and if you think you have whitefly will become covered surprisingly quickly. They also serve as a good early warning for if you suspect that you will get whitefly which can then be followed up by a more effective removal method as the next step up.

    Biological control. Biological control of a pest relies on introducing a predator species so "fighting nature with nature", if chosen carefully, the predator will stop damage to your plants without damaging the environment. Such biological controls are safe for the user, children and pets. They will not harm other beneficial garden insects and are biodegradable.

They do rely on the predator always having some food though, or they will die out, so like other organic practices it is a question of maintaining a small population of pests to allow the predators to be ready for them.

The biological control for whitefly is the parasitic wasp, Encarsia formosa. These minute little wasp's parasitise the whitefly pupae. This turns the pupae black after a period of about 10-14 days depending on temperature. From these pupae will emerge Encarsia formosa instead of whitefly therefore controlling them. One wasp in the right conditions can parasitise up to 150 whitefly. These wasps are harmless to all other insects and animals. For effective control, regular introductions should be carried out.
 

Encarsia is only suitable for glasshouses and conservatories. Encarsia needs a 24 hour average temperature in the glasshouse of at least 17°C

---