Tiny whiteflies are sap-sucking insects that can become abundant in vegetable and ornamental plantings, especially during warm weather. Despite their name, whiteflies are not true flies but are in the order Hemiptera, related to aphids, scales, and mealybugs. They derive their name from the mealy white wax covering the adult’s wings and body. Adults are tiny insects with yellowish bodies and four whitish wings. Although adults of some species have distinctive wing markings, many species are most readily distinguished in the last nymphal (immature) stage, which is wingless and lacks visible legs. Whiteflies normally lay their tiny oblong eggs on the undersides of leaves. The eggs hatch, and the young whiteflies gradually increase in size through four nymphal stages called instars. The first nymphal stage (crawler) is barely visible even with a hand lens. The crawlers move around for several hours before settling to begin feeding.

Whiteflies can be as small as 1/12 of an inch, are somewhat triangular in shape, and are often found in clusters on the undersides of leaves. They are moth-like in appearance, about 1/16th of an inch in length with an elongated, somewhat triangular shape, and are most often gray-white in coloring. Whiteflies have yellow or orange bodies with a waxy coating that makes them appear white.

Whiteflies can cause leaf damage and a host of other problems by feeding on plant sap. They are similar to aphids in the kind of damage they cause. Both have piercing-sucking mouthparts that they use to extract plant sap, causing foliage damage and stunted growth. They secrete a sticky substance known as honeydew, which promotes fungal diseases such as black sooty mold. Whiteflies do the most damage as juveniles, their nymph stage. They feed in large masses on the undersides of leaves, sucking up the plant juices. They produce honeydew and are the cause of the yellowing of leaves, and ultimately they can lead to the death of the plant. Often a black sooty mold will form on the leaves.

In summary, tiny whiteflies are sap-sucking insects that are not true flies but are in the order Hemiptera, related to aphids, scales, and mealybugs. They derive their name from the mealy white wax covering the adult’s wings and body. Whiteflies normally lay their tiny oblong eggs on the undersides of leaves. They can cause leaf damage and a host of other problems by feeding on plant sap and producing honeydew.