At the first sign of them you want to take action as they multiply like crazy.  It is the nymph and adult fly that cause physical damage to the host plants. They attack the leaves, buds and stems sucking the juice out of them. Without control infested plants will turn yellow, growth become stunted and ultimately die.

Whiteflies can seem to come out of nowhere all of a sudden! They are easy to identify. When you move or water your plants and you see what looks like an instant snowstorm with minute things flitting all over, you've got whiteflies!

Whiteflies are not well controlled with any available insecticides. In many situations, natural enemies will provide adequate control of whiteflies; outbreaks may occur if natural enemies that provide biological control of whiteflies are disrupted by insecticide applications, dusty conditions, or interference by ants. Avoid or remove plants that repeatedly host high populations of whiteflies.

In gardens, whitefly populations in the early stages of population development can be held down by a vigilant program of removing infested leaves, vacuuming adults, or hosing down (syringing) with water sprays. Aluminum foil or reflective mulches can repel whiteflies from vegetable gardens, and sticky traps can be used to monitor or, at high levels, reduce whitefly numbers. If you choose to use insecticides, insecticidal soaps or oils such as neem oil may reduce but not eliminate populations.

How to be Tough in Treating White Flies

Biological Control
Avoiding the use of insecticides that kill natural enemies is a very important aspect of whitefly management. Products containing carbaryl, pyrethroids, diazinon or foliar sprays of imidacloprid can be particularly disruptive. Control of dust and ants, which protect whiteflies from their natural enemies, can also be important, especially in citrus or other trees. Avoid using other pesticides to control whiteflies; not only do most of them kill natural enemies, whiteflies quickly build up resistance to them, and most are not very effective in garden situations.
Removal
Hand-removal of leaves heavily infested with the nonmobile nymphal and pupal stages may reduce populations to levels that natural enemies can contain. Water sprays (syringing) may also be useful in dislodging adults.

A small, hand-held, battery-operated vacuum cleaner has also been recommended for vacuuming adults off leaves. Vacuum in the early morning or other times when it is cool and whiteflies are sluggish. Kill vacuumed insects by placing the vacuum bag in a plastic bag and freezing it overnight. Contents may be disposed of the next day.
Traps
In vegetable gardens, yellow sticky traps can be posted around the garden to trap adults. Such traps won't eliminate damaging populations but may reduce them somewhat as a component of an integrated management program relying on multiple tactics. Whiteflies do not fly very far, so many traps may be needed. You may need as many as one trap for every two large plants, with the sticky yellow part of the trap level with the whitefly infestation. Place traps so the sticky side faces plants but is out of direct sunlight.

Commercial traps are commonly available, or you can make traps out of 1/4-inch plywood or masonite board, painted bright yellow and mounted on pointed wooden stakes that can be driven into the soil close to the plants that are to be protected. Although commercially available sticky substrates such as Stickem or Tanglefoot are commonly used as coatings for the traps, you might want to try to make your own adhesive from one-part petroleum jelly or mineral oil and one-part household detergent. This material can be cleaned off boards easily with soap and water, whereas a commercial solvent must be used to remove the other adhesives. Periodic cleaning is essential to remove insects and debris from the boards and maintain the sticky surface.

For more easy steps and guide, check out our main page here:

Auckland fly control