What are White Flies?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.
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.