Whiteflies can quickly develop insecticide resistance. In particular, the silverleaf whitefly is resistant to a wide range of insecticides. For this reason, the best strategy is to prevent problems from developing. Avoid or remove plants that repeatedly host high populations of whiteflies. In the early stages of population development, whiteflies can be reduced by removing infested leaves or hosing down with water, or even by vacuuming. If you choose to use insecticides, insecticidal soaps or petroleum spray oils may reduce, but will not eliminate, populations. Most insecticides used are only effective against adults, so that repeated treatments at three to five day intervals are necessary for several weeks before control can be achieved. Make sure that the undersides of the leaves are treated. Neem oil, pyrethroid insecticides like bioallethrin and piperonyl and low toxicity systemic sprays like imidacloprid and acetamiprid are registered to control whitefly. Follow label directions for application advice.
In many situations, natural enemies will provide some control of whiteflies. Effectiveness of natural enemies will be reduced by insecticides, dusty conditions, or interference by ants. Several insect species that feed on whitefly may be found in the suburban backyard. These including lacewings, ladybirds and syrphids (hover flies). The biological control agent Encarsia formosa is a small, parasitic wasp that attacks both greenhouse and silverleaf whiteflies. Encarsia is, however, more effective against the greenhouse whitefly. It is sold as parasitised greenhouse whitefly pupae that are glued onto small cards and is available commercially for use by greenhouse growers.