E-432 Whiteflies Carlos E. Bográn and Kevin M. Heinz* can move and disperse over long distances by flying lthough there are approximately 1,200 species upward and being picked up and carried by air cur- of whiteflies worldwide, only a few species are rents. Eggs are usually laid on the underside of young Aof economic importance. Most whitefly species leaves and may be deposited randomly throughout have a narrow range of host plants, but the ones that the leaf, in circles, arcs or spirals, depending on the are considered pests may feed on and damage many species. vegetable and field crops, greenhouse and nursery The eggs hatch into mobile first instars called crops and house plants. crawlers, which search and find a suitable feeding The name whitefly is site. They then insert their mouthparts and remain in derived from the generally one place for the rest of their immature stages. white, wax-like substance that Second to fourth instars are called nymphs and coats their bodies, particularly resemble small scale insects. Nymphs are oval and the wings. Some species are may be pale yellow to black, depending on the dark with colored wing pat- species. The late fourth instar is also known as “pupa” Bastiaan Drees, TAMU terns. All developmental stages because mobile adults emerge from the exoskeleton of secrete wax, and in nymphs (immatures), the appear- sessile nymphs after development is complete. ance of accumulated wax filaments and plates is used Silverleaf whitefly fourth instars are also known as in species identification. “red-eye nymphs” because the relatively large eyes of The main whitefly species that feed on ornamental the developing adult are already visible through the plants in Texas are the silverleaf whitefly (Bemisia nymph integument (skin) during this stage. argentifolii [Bellows & Perring]), the greenhouse white- The complete life cycle varies from about 21/2 to 5 fly (Trialeurodes vaporariorum [Westwood]) and the weeks according to temperature conditions and banded wing whitefly (Trialeurodes abutiloneus species. Many overlapping generations can occur each [Haldeman]). Other species include the citrus blackfly year. Adults and nymphs feed by inserting their (Aleurocanthus woglumi Ashby), the citrus whitefly mouthparts into plant tissue and sucking phloem sap. (Dialeurodes citri Ashmead) and the giant whitefly (Aleurodicus dugesii Cockerell). It is important to dis- Silverleaf Whitefly tinguish the different whiteflies because damage The silverleaf whitefly is the potential and susceptibility to control differs by most economically important species. whitefly species in Texas. Adults are 0.8-1.2 millimeter long with Description and iLfe Cycle white wings (without markings) Carlos Bogran, TAMU and pale yellow bodies. The wings are held in a roof- Whiteflies are small insects (1 to 3 millimeter). like position (about a 45-degree angle) over their bod- Adults have four broad wings of approximately the ies, whereas other whiteflies typically hold the wings same size. The adult is the most mobile stage and is nearly flat when at rest. As a result, the silverleaf responsible for colonizing the host plant. Whiteflies whitefly appears more slender than other common whiteflies. Eggs are oblong, smooth and yellow to *Assistant Professor & Extension Specialist and Associate Professor of Entomology, The Texas A&M University System amber brown and are laid randomly on the underside of leaves. Nymphs are greenish-yellow, oval and flat. color. Adult citrus blackflies are 1.3-1.6 millimeter Late third and fourth instars develop distinctive eye long with slate-blue wings and red abdomens. spots and are often referred to as red-eyed nymphs. Females lay eggs in a characteristic spiral pattern. Silverleaf whitefly pupae are oval, flattened (with Nymphs and pupae are dark black, with a fringe of tapering sides) and lack the marginal fringe of wax fil- white wax filaments along the upper perimeter. aments common to other whiteflies. Their hosts Citrus whiteflies are an occasional pest of citrus in include more than 500 species representing 74 plant southern Texas but may also attack ornamental plants families. and trees such as Boston ivy, chinaberry, laurel cher- Greenhouse Whitefly ry, crepe myrtle, English ivy, gardenia, green ash, jas- mine, osage orange, prickly ash, trumpet vine, water This is an occasional pest, oak, persimmon and wild olive. Adults are very simi- especially in greenhouses. lar to adult greenhouse whiteflies but have broader Adults are about the same size wings and feed mainly on shrubs and trees, especially as the silverleaf whitefly (0.9- citrus. Nymphs and pupae are similar to those of the 1.1 millimeter). The wings are silverleaf whitefly but are much rounder in shape. held nearly parallel to the leaf Michael Parrella, U. California and cover the abdomen when Davis Giant whitefly adults are about three times larger at rest. Eggs are occasionally laid in circular patterns than other common whiteflies. Wings overlap when on plants with smooth leaves. Eggs are oblong, at rest and are mottled with grey markings. Common smooth and are initially yellow but darken before hosts include bamboo, begonia, bird of paradise, cit- hatching. Pupae are oval, slightly raised (with vertical rus, geranium, hibiscus, ivy, jasmine, morning glory, sides) and have a fringe of wax filaments along the lantana, passion flower, philodendron and pittospori- perimeter of their upper surface. Relatively large wax um. Nymphs and pupae secrete long cylindrical filaments project from their bodies; the number and strands of wax extending up to two inches (50 mil- length of these filaments varies with the host plant. limeters) from the leaf surface. Accumulation of these Their hosts include more than 200 plant species. wax strands resembles fluffy-white hair. Females deposit eggs and wax in spiral patterns that appear as Bandedwinged Whitefly white concentric circles on the undersides of host This is an occasional pest of plant leaves. crops and ornamental plants, especially hibiscus. The adults are slightly larger than silver- Damage leaf and greenhouse whiteflies. Whiteflies can damage plants directly or indirectly. They can be recognized by two Carlos Bogran. TAMU Direct damage is caused through their feeding, which irregularly shaped (in zig-zag removes plant sap and stunts plant growth, especially pattern) gray bands on the front pair of wings. Except in young plants. Silverleaf whitefly feeding has been for these banded front wings, the adults are very simi- associated with several plant disorders, including sil- lar in size and shape to adult greenhouse whiteflies. verleaf of squash, stem blanching and whitening of poinsettia and cruciferous vegetables, and irregular The eggs are oblong and smooth and may be laid ripening of tomatoes. Indirect whitefly damage is irregularly or in neat circles on the leaves, depending caused by the large amounts of sticky honeydew on the host plant species. Eggs are pale yellow and secreted during feeding. Honeydew may cover plants turn pink before hatching. Pupae are oval, slightly and support the growth of sooty mold, which reduces raised (with vertical sides) and have a fringe of wax the plant’s ability to use light filaments along the upper perimeter. Pupae have a for photosynthesis. In addition dark area in the upper surface of the integument, to direct and indirect damage, which distinguishes them from the pupae of green- whiteflies may carry and trans- house whiteflies. Important ornamental hosts include mit viral diseases that can poinsettia, geranium, hibiscus and petunia. severely damage susceptible Bastiaan Drees, TAMU Other Whitefly Species plants. The citrus blackfly is a spo- radic pest of ornamental plants and a potentially serious pest of citrus, especially in South Texas. Both nymphs and adults are easily distinguished from other Bastiaan Drees, TAMU whitefly species by their dark 2 I Break the whitefly reproductive cycle by having Integrated Pest Management periods of time with no host plants in the green- Integrated pest management (IPM) is a strategy to house or garden. avoid or prevent pest damage with minimum adverse impact to human health, environment and non-target organisms. Successful IPM of whiteflies involves: Pest Monitoring and I Implementing cultural control practices to limit Diagnosis whitefly colonization. Whiteflies, like many other pests, reproduce very I Frequent monitoring of populations. rapidly. A single female may lay 150-300 eggs during her lifetime. When temperatures are high at the peak I Accurate species identification and pest diagno- of summer, whiteflies may complete development in sis to select proper control action. 16-18 days. In the absence of natural enemies and I Using pertinent information to decide when other natural control factors such as heavy rain, a few treatment is necessary. individuals can produce thousands in a very short time. Therefore, it is important to monitor plants fre- I Using effective pest management tools, including quently. Do not wait until damage is obvious because tolerant species or varieties (when available), whitefly control is very difficult to achieve at that natural enemies and insecticides. point. Inspect the undersides of old and new leaves weekly for all whitefly stages. The more plants you inspect, the more likely you will be to detect prob- Cultural Control lems sooner, when management is easier. Record the Cultural control practices are number of whiteflies per plant or the percentage of aimed at avoiding or preventing plants infested. This information is critical in deciding whitefly infestations, eliminat- whether or not treatment is necessary. ing sources of whiteflies and keeping whiteflies out of grow- Although yellow sticky traps sold at garden stores ing areas. To implement cultur- Bastiaan Drees, TAMU may be used to detect when and where whitefly al control you should: adults are occurring, they are not useful in estimating population density on plants. They should be placed I Thoroughly inspect new plants before purchase just above the plant canopy and must be checked and and reject or treat any infested material.