How to control whitefly

White fly can be a real menace in glasshouses in late summer and autumn. It is difficult to control as they reproduce very very quickly.

Winter is the time to start controlling whitefly.

In cold climates whiteflies usually over winter on indoor plants or in greenhouses.

The best way to control whiteflies is by using a combination of techniques. Pesticides, such as Orthene are effective but need to be combined with good garden hygiene and winter spraying of all seasons spraying oil. Whenever possible remove and destroy heavily infested foliage. If a particular plant is prone to whiteflies, you may want to avoid planting it again.

In summer you don’t notice individual whitefly; rather, you see a cloud of them when you shake or disturb an infested plant. The tiny adults and even smaller white, scale like nymphs can be found under leaves. Mature whitefly are 2 -3 mm long and resemble a tiny white moth.

Adult whitefly and nymphs both suck plant juices. In heavy infestations leaves may turn yellow and may drop prematurely. Their favourite plants include tomatoes, beans, melons, squash, peppers, fuchsias, hibiscus, geraniums, and citrus. In warm, dry, weather whitefly populations surge. Adults, nymphs, and pupae may all be present at once making it very difficult to control.

Adult whitefly are attracted to yellow, so you can trap them by putting yellow cards coated with a petroleum jelly near infested plants.

For additional information
http://www.crop.cri.nz/home/products-services/publications/broadsheets/93.pdf
http://www.rnzih.org.nz/Plant_Doctor/WG156_Whitefly_infestation.htm