Plant pest
Plant Problems

Whitefly or Whiteflies on Plants 

Whiteflies are a serious garden and plant pest and should be controlled as soon as they are found. If whitefly are allowed to multiply, then the infestation can do serious harm. There are several ways for controlling whiteflies, together with effective methods to kill them.

Whitefly or whiteflies are probably one of the most easily recognized and identified of all garden and plant pests.

Individually, whiteflies are just a few millimetres from head to tip of tail - about the size of a pinhead! They usually fly around in clouds when disturbed, and otherwise, are happy to carry on sucking the sap out of your plants from the underside of the leaves. Unmistakably white, they are shaped like miniature moths.

As well as sucking the sap out of plants, they excrete  a sticky honeydew - typical of aphids to which they are related. The honeydew in turn attracts sooty mould and other fungal diseases.

Whiteflies are not the easiest of insect pests to control, so prompt action is required as soon as any are found. It will probably need several applications of a suitable insecticide, and the manufacturer's spraying schedule should be followed.

Systemic insecticides are best. Insecticides containing Permethrin or Bifenthrin seem to do the trick. If the infestation is on edible plants or vegetables - and in particular they can be a plague on Brassicas - then Bifenthrin would be the preferred option. Again, follow the manufacturer's recommendations regarding cropping periods after application. Some types of Whiteflies have developed a resistance to certain chemical sprays, making them very difficult to control. If you have ongoing problems with whiteflies, then try alternating the type of chemical spray.

Whitefly in the Greenhouse

Fuchsias in particular are susceptible to whitefly attack - especially when grown under glass - or indoors. In the greenhouse, there are biological controls available. Another option is to 'catch' the whitefly with sticky yellow flycatcher cards.

If there is a severe infestation, then a great way of reducing the numbers in a short time, is by the use of a portable vacuum cleaner - such as a CarVac. Woks  wonders until you can get the other orthodox controls taking effect.

Don't ignore whiteflies. They will not simply go away! Be vigilant as soon as plants break into leaf right after the winter break, and also inspect the undersides of leaves for whitefly during mild winter periods.

A wide range of plants are susceptible to whitefly attacks including Fuchsias, Brassicas, Dahlias, and more or less any crops grown under glass. Mottling or yellowing of leaf surface is often the first sign of an infestation, as the juveniles hatch from the eggs laid on the underside of leaves and start to tuck into the ready supply of food! A\parasitic wasp - Encarsia formosa - can be successful for commercial applications. This avenue seems to be less successful with whitefly infestations in domestic situations.

By David Hughes - 

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