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.
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.