Whitefly look like tiny white moths. They feed on the undersides of the leaves but flutter around the plant when they are disturbed. Both the adults and the larvae suck the sap of the host plants and disfigure the foliage with deposits of sticky honeydew which quickly become covered with sooty black mould growth. Whitefly infestations therefore spoil the appearance of the plants as well as weakening their growth.
Reproduction is by eggs which are laid on the underside of the leaf. Wingless larvae hatching from these eggs quickly settle down to feed on the plant sap and eventually pass into the short pupal stage before emerging as winged adults.
Most plants may be subject to attack but Abutilon, begonia, calceolaria, chrysanthemum, fuchsia and Impatiens are the most susceptible.
Whitefly are difficult to control because the larvae and pupal stages are resistant to most insecticides. They are best controlled by synthetic pyrethrins such as bioresmethrin or permethrin. Insecticides based on pirimiphos-methyl are also effective. Three or four repeat sprays at 4-7 day intervals are, however, needed to obtain complete control of the pests and care must be taken to spray the undersides of the leaves.