Crape Myrtle & Whiteflies
- Whiteflies are tiny flying insects closely related to mealybugs, scale insects and aphids. Adult whiteflies are approximately 1/10 inch long. Their pale yellow bodies and four white wings are covered in a layer of powdery white wax. Their nymphs are oval-shaped with flattened bodies and resemble scale insects. Whiteflies congregate to feed, and large clouds of the insects may fly from a severely infested crape myrtle if the tree is disturbed.
- Adult female whiteflies lay hundreds of eggs on the lower surfaces of crape myrtle leaves. The eggs hatch into crawlers in approximately a week. They crawl for a short period after hatching and then lose their mobility. Whiteflies go through four stages of development, or instars, before maturing into adults. The pupae vary in appearance depending on the species of whitefly. The entire life cycle from egg to death takes place over a one-month period, so multiple generations appear on crape myrtle trees simultaneously.
- Whiteflies pierce crape myrtle foliage with their piercing mouthparts and drain sap from the leaves. Infested leaves turn yellow and fall from the plant. The constant loss of sap and subsequent defoliation weakens the tree and stunts its growth. Severe infestations can kill plants. Some types of whiteflies also transmit viruses between hosts. Whiteflies ingest more sap than their bodies need, so they exude large amounts of a sticky-sweet liquid called honeydew. Honeydew acts as a growing medium for a thick, unsightly black fungus called sooty mold.
- Whiteflies are difficult to control and spread quickly from infested crape myrtles to other plants. They quickly develop resistance to traditional insecticides. Insecticides kill the adults and crawlers, but do not harm the eggs or pupae. You can prevent whitefly infestations by carefully examining all new plants before purchase and by quarantining the plant for several days before placing it near other plants. You can control infestations by vacuuming the insects from the tree and then placing the bag in the freezer to kill the insects. Some predatory insects such as lacewings, lady beetles and pirate bugs feed on whiteflies. Insecticidal soaps and horticultural oils also help limit infestations.
