Whiteflies Resource - Newly Updated!

The summer is winding down, but many warm-weather pests, like whiteflies are still going strong. Whiteflies are tiny white insects commonly found in vegetable garden and landscape plantings in large numbers. Often they fly around plants when disturbed, which is when people first notice them.

Despite their name, whiteflies are not true flies but are actually related to aphids, scales and mealybugs. Like these insects, whiteflies cause damage when they suck plant juices from leaves, which yellow or die off. Whiteflies excrete excess liquid called honeydew that is sticky, and may be covered with black sooty mold. The honeydew also attracts ants, which disrupt naturally-occurring beneficial insects that may help control whiteflies and other plant pests. Outbreaks of whiteflies commonly occur when these “natural enemies” are disrupted by insecticide applications, dusty conditions, or interference from ants.

Whiteflies usually occur in groups on the undersides of plant leaves. Adults are tiny insects with yellowish bodies and 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.

Most whiteflies have a wide host range that includes numerous weeds and crops. In many parts of California, they breed all year, moving from one host to another as plants are harvested or dry up.

Learn how to manage whiteflies and prevent future infestations by reading the newly revised UC IPM Pest Note: Whiteflies by author and retired entomologist, Dr. Mary Louise Flint.