Whitefles often infest shade trees.
Trees often have many insects and bugs flying around them. Whiteflies are very small, white insects that are commonly found feeding on the leaves of citrus, shade and ornamental trees. Whiteflies can become a nuisance when present in large numbers and they are often difficult for home owners to control.
Identification
Whiteflies are not actually flies, but related to aphids and psyllids. These pests are typically 1/16 inches in length, are white in color and have wings. Adult whiteflies lay their eggs on host tree leaves and after hatching crawlers emerge. Once crawlers begin feeding on plant tissue, they molt into nymphs. Nymphs are flat, light green in color and have white, wax protruding from their bodies. Eventually, the nymphs become adult whiteflies and the life cycle begins all over again. Whiteflies usually fly up when infested plants or trees are shaken and settle back onto the tree shortly.
Effects
Whiteflies feed on tree leaves with piercing mouthparts, removing sap from the leaves. Feeding causes tree leaves to turn yellow, become distorted, twist, wither and drop from the tree prematurely. Trees infested with whiteflies may become stunted and develop a fungal disease known as sooty mold. Sooty mold is caused by the whitefly excreting honeydew, which is a gooey substance that adheres to the tree leaves and branches. Once honeydew is present, fungi sticks to it and causes sooty mold to develop. Sooty mold is a black, crusty fungal growth that covers a large portion of the infested tree. As long as whiteflies are feeding on a tree, sooty mold will be a problem. Although sooty mold does not usually kill trees, it can cause poor health and vigor due to decreased sunlight absorption. This is only a problem on trees with heavy coverings of sooty mold fungi.
Cultural Control
Beneficial insects such as pirate bugs, lady beetles and parasitic wasps are predators that feed on whiteflies. If beneficial insects are feeding on whiteflies, avoid using insecticides because these products will kill beneficial insects. Yellow sticky traps are often effective in controlling light infestations of whiteflies. Whiteflies are attracted to yellow and get stuck in the trap and die.
Chemical Control
Insecticidal soaps are recommended in whitefly control and are available at your local garden center. These products work on contact with the pest, so be sure to cover the tree leaves thoroughly. Concentrate on the undersides of plant leaves where whiteflies congregate to feed. Horticultural oils are also used to control whitefly infestations. These products coat the pest with oil and suffocate them. Applying horticultural oils to your tree may also help keep sooty mold loose and easy to remove. Strong insecticides with the active ingredient malathion or nicotine sulfate are available for whitefly control. Always apply these products strictly according to the label directions for best results.
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