Whiteflies

Whiteflies are tiny, flying insects that derive their name from the mealy white wax covering their wings and body. While adult whiteflies are similar in appearance, the immature stages are more distinctive. The pupa and other immature stages of the woolly whitefly are covered with curly, waxy filaments and are exclusively found on the undersides of leaves; pupae of the bayberry whitefly have a clear wax fringe around the body margin; pupae of the citrus whitefly have a distinctive Y-shape on their backs; and pupae of the ash whitefly have a thick band of wax down the back and a fringe of tiny tubes, each with a liquid droplet at the end.

Whiteflies suck phloem sap, which in some cases can cause leaves to wilt and drop when there are high numbers of whiteflies. However, the primary concern with whiteflies is the honeydew they produce. Honeydew excreted by nymphs and adults collects dust and supports the growth of sooty mold; large infestations blacken entire trees, including fruit, as well as attract ants, which interfere with the biological control of whiteflies and other pests. The sooty mold can also affect tree yields by reducing photosynthesis and requiring extra handling time for cleaning.

Applying insecticides for whiteflies is generally not necessary; exceptions are usually limited to where biological control has been severely disrupted. Enhance biological control by avoiding nonselective insecticides for other pests and by controlling sugar-feeding ants.

Several natural enemies attack the immature stages of whiteflies and provide partial to complete biological control when undisturbed by ants, dust, or an insecticide application. Conserve natural enemies by controlling other pests with the least disruptive pesticides available and by controlling sugar-feeding ants.

Alternate row pruning to provide refuge for parasites may provide some benefits.

Inspect for whitefly throughout summer by looking for immature stages on the undersides of leaves directly above areas with honeydew, sooty mold, or both. Consider applying an insecticide if honeydew and sooty mold contamination of fruit reaches levels that are not tolerable. Applications specifically targeting whitefly are usually not needed because usually at least one neonicotinoid (e.g., Assail, Admire Pro, Nuprid) or insect growth regulator (e.g., Esteem, Centaur) that will suppress whiteflies has already been used one or more times on most citrus orchards to control scale and sharpshooter pests. No official treatment thresholds for whitefly exist.