Whiteflies 

 Whiteflies are common pests on many ornamental plants. Some plants most frequently attacked include allamanda, chinaberry, citrus, fringe tree, gardenia, ligustrum, viburnum, persimmon, and many annuals. Adult whiteflies resemble tiny white moths; however, they are not closely related to moths but are more related to scale insects. They are only about 1/16 inch long and have four wings. The wings and body are covered with a fine white powdery wax. The immature stages (nymphs) which are found on the underside of leaves are flat, oval in outline, and slightly smaller than a pin head. They are light green to whitish and somewhat transparent. A generalized life cycle of the whitefly is as follows: The eggs are laid on the undersides of the leaves and hatch in 4 to 12 days into active, six legged nymphs (crawlers). The crawlers move about for several hours, then insert their mouthparts into the leaves and remain in one place for the rest of their immature stages. After molting three times they pupate (resting stage) and are transformed into the adult. The length of the life cycle from egg to adult varies considerably, requiring from 6 weeks to 6 months (winter generation). There are three major generations or broods of whiteflies.

Whiteflies have piercing-sucking mouthparts with which they puncture the leaf and suck the plant juices. Top sides of leaves on infested plants become pale or spotted due to these insects feeding on the undersides of the leaves. Whiteflies as well as soft scales, mealybugs, and aphids excrete large amounts of honeydew which provides an excellent medium for the growth of a black fungus called sooty mold. Besides being unattractive, sooty mold interferes with photosynthesis, somewhat retards the growth of the plant, and causes early leaf drop. Sooty mold usually weathers away following control of the insect infestation. Ants feed on the honeydew and when ants are noticed, plants should be examined closely for these sucking pests. Carefully examine plants susceptible to whitefly infestations with the aid of a hand lens for evidence of the parasite. Parasitized whitefly nymphs will contain the larva or pupa of the parasite or the parasite emergency hole can be seen in the whitefly nymph. The parasite does not attack the adult whitefly. If parasitism is evident, do not apply a pesticide. Chemical control will kill the pest and prevent damage to your trees. During recent years, the silverleaf (sweetpotato) has been the major whitefly species attacking ornamental plants. This whitefly is easily controlled with IMICIDE®.