The crawlers move around for several hours before settling to begin feeding. The first nymphal stage (crawler) is barely visible even with a hand lens. The eggs hatch, and the young whiteflies gradually increase in size through four nymphal stages called instars. Whiteflies normally lay their tiny oblong eggs on the undersides of leaves. Table 1 lists common whiteflies in California gardens and landscapes. Other species of whiteflies, especially those on woody species, often have a more limited host range. For more information on this species, see Pest Notes: Giant Whitefly. It is now found in coastal areas and interior valleys in much of the state on a number of tropical and semi-tropical ornamental species. These species breed all year round in warmer parts of California, moving from one host to another as plants are harvested or dry up.Īnother species of whitefly with a broad host range is the giant whitefly, Aleurodicus dugesii, which invaded Southern California in the early 1990s. The most common pest species-such as greenhouse whitefly ( Trialeurodes vaporariorum) and sweetpotato whitefly ( Bemisia tabaci)-have a wide host range that includes many weeds and crops. Large colonies often develop on the undersides of leaves. Whiteflies develop rapidly in warm weather, and populations can build up quickly in situations where natural enemies are ineffective and when weather and host plants favor outbreaks. Depending on species, whitefly nymphs vary in color from almost transparent yellow or whitish to black with a white fringe ( Table 1). 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. Adults are tiny insects with yellowish bodies and four whitish wings. They derive their name from the mealy white wax covering the adult’s wings and body. IDENTIFICATION AND LIFE CYCLEĭespite their name, whiteflies are not true flies (in the insect order Diptera) but are in the order Hemiptera, related to aphids, scales and mealybugs. Management is difficult once populations are high. Outbreaks often occur when the natural biological control is disrupted. They excrete sticky honeydew and cause yellowing or death of leaves. Whiteflies are tiny, sap-sucking insects that may become abundant in vegetable and ornamental plantings, especially during warm weather. Greenhouse whitefly nymphs turn black when they are parasitized.
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