Trialeurodes vaporariorum (Westwood)
The greenhouse whitefly crawler has four or possibly five leg segments and two to three antennal segments. Segmentation is not clear and most specimens will appear to have only three leg segments and two antennal segments. The crawler may be transparent to opaque, ranging in color from light green to yellow, light brown through dark brown and black. Small amounts of powdery white wax are usually produced after the crawler settles and begins feeding. The pupal cases of this species can vary depending on the leaf surface (glabrous vs. hairy). When seen from the side, greenhouse whitefly pupae are circular with flat tops, like a tuna fish can, with the filaments emerging from the top of the can. Silverleaf and sweetpotato whitefly pupae are convex in shape without the flat top and more yellowish. While the sex ratio of the greenhouse whitefly is normally 1:1, bisexual ('American') and parthenogenetic
('English') races of this species have been reported.
Movement of the greenhouse whitefly takes place during the first few days after emergence. The distances covered are usually only a few meters. Most feeding and oviposition takes places on the upper leaves. Studies have shown that the greenhouse whitefly prefers young leaves. Aggregation of the greenhouse whitefly is very strong, even on a relatively unsuitable host plant such as tomato.
The host range of the greenhouse whitefly is estimated at about 200 plant species, mostly in the families Cruciferae, Leguminosae, Malvaceae, and Solanaceae. The insect may attack far more plant species in the greenhouse environment.
The greenhouse whitefly is a pest of many greenhouse vegetables and ornamentals. This pest is a
vector of Lettuce infectious yellow virus.
Management of whiteflies is difficult. Successful management of whiteflies requires an integrated program that focuses on prevention and relies on
cultural and biological control methods when possible. While insecticides will be required in most programs, they should be selected carefully and used only when shown to be needed by a regular monitoring program. Insecticide applications often fail to provide adequate control and whiteflies are able to rapidly increase in numbers when conditions are ideal. An integrated pest management program, combining the use of cultural and biological methods and selective insecticides when necessary, is essential for effective management of whiteflies in greenhouses. Maintain and monitor yellow sticky traps to detect invasions early.
The greenhouse whitefly has developed resistance to certain insecticides and this problem is compounded by the fact that few insecticides are registered for greenhouse use.
The important role of natural enemies in reducing populations of greenhouse whitefly has been well established. However, the high development rate of the greenhouse whitefly requires an efficient system to produce parasitoids for inundative releases against this pest. While successfully biological control programs have been developed, the greenhouse whitefly cannot be controlled effectively on all important crops. Releases of the parasitic wasp, Encarsia formosa, have been successful in controlling greenhouse whitefly under experimental
conditions and are widely used in Europe in glasshouse vegetable production. Black, parasitized greenhouse whitefly fourth instars should begin to appear within 2 to 3 weeks of the first release against greenhouse whitefly.
Parts of this material may be reproduced for educational use. Please credit "United States Department of Agriculture, WHITEFLY KNOWLEDGEBASE"