In 1994, the ‘B’ biotype of the sweetpotato whitefly was described as a new species, Bemisia argentifolii Bellows & Perring, and became known commonly as the silverleaf whitefly, but is not accepted by all taxonomists and some consider it the same as Bemisia tabaci. In March, 2005, researchers from University of Arizona and University of California independently identified the ‘Q’ strain of Bemisia tabaci which they believe originated in the Mediterranean region and has shown resistance to many insecticides and has a large host list.

For more Q Biotype information see:
The Q Biotype of Bemisia Tabaci in the U.S. and Management Suggestions
Important Update: Control of Q and B Biotype Whiteflies!

Except for slightly smaller size, slightly more yellowish color, and slightly more slender appearance, silverleaf whiteflies resemble other whiteflies. The eggs are tiny, cylindrical, white to brownish, and inserted into the leaf tissue on the underside of the leaf. Nymphs are translucent, pale yellow, flat scale-like insects that feed on the lower leaf surface (this is the "egg" stage that growers refer to). Silverleaf whitefly pupae are pale yellow, scale- like insects that sometimes have noticeable waxy hairs (sometimes they appear to be bare). The sides are not perpendicular and there is no tiny fringe of waxy filaments around the margin.

Silverleaf whiteflies infest ornamentals and vegetables grown in commercial greenhouses. It is especially attracted to poinsettias, gerbera daises, and hibiscus. This whitefly is troublesome on poinsettias because as the bracts mature they become increasingly sensitive to pesticides.

Infested plants become sticky with honeydew and dark with sooty molds. Silverleaf whitefly "crawlers" hatch and crawl about until they insert thread-like mouthparts into the lower surface of the leaf to feed. They tuck the legs and antennae underneath and settle down closely to the leaf surface. Crawlers molt into scale-like nymphs that also suck out sap. Nymphs grow and molt a second and third time into a nonfeeding state called the pupa. The adult whitefly develops within the pupa. Adults emerge from the pupal skin through a T-shaped slit about a month after the time the egg was laid.

Females live about four weeks and lay 28 to 300 eggs each on the lower leaf surface. In hot weather, development may take only two weeks; in cool weather, development takes much longer.

Figure 1. Silverleaf whitefly.

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Figure 1. Silverleaf whitefly.

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Figure 2. Silverleaf whitefly (A) adult (B) egg (C) crawler (D) pupa.

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Figure 2. Silverleaf whitefly (A) adult (B) egg (C) crawler (D) pupa.

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Growers should inspect all plant material before it is introduced into a greenhouse. Infested plants should be returned to the propagator or destroyed. Vents and doors should be covered with fine mesh screening materials. All workers and visitors to the greenhouse should avoid wearing yellow, green or blue clothing.

The silverleaf whitefly is resistant to many pesticides. Successful control depends on selecting pesticides to which the whiteflies are somewhat susceptible, and then conscientiously applying them and other control measures in a well organized pest management program. There are biological control agents available for management.

A specific control strategy that would suit all situations would be difficult to suggest here, but rotation of pesticides in different chemical classes is the important in any management strategy. If there are any questions about which biotype is involved, seek proper identification. As the days become cooler, it will be necessary to extend the length of treatment period from three weeks to four weeks (and probably five weeks in late December and early January). It seems unlikely that whiteflies will quickly become resistant to soap. Soap controls adults and young nymphs but will not kill eggs nor older nymphs. Soap can be phytotoxic to some ornamental plants (especially the bracts of poinsettias).

See more information in the North Carolina Agricultural Chemicals Manual.

Recommendations of specific chemicals are based upon information on the manufacturer's label and performance in a limited number of trials. Because environmental conditions and methods of application by growers may vary widely, performance of the chemical will not always conform to the safety and pest control standards indicated by experimental data.

• Important Update: Control of Q and B Biotype Whiteflies! Bethke, J. et al. 2005. American Nursery & Landscape Association,Society of American Florists.
• Insect and Related Pests of Flowers and Foliage Plants. Baker, J. R. ed. 1994 (revised). N.C. Cooperative Extension pub. AG-136.
• Sweetpotato Whitefly B Biotype, Bemisia tabaci (Gennadius) (Insecta: Hemiptera: Aleyrodidae). McAuslane, H. J. and H. A. Smith. 2015 (revised). University of Florida IFAS Extension, EDIS. Publication #EENY-129.
• The Q Biotype of Bemisia tabaci in the U. S. and Management Suggestions. Sanderson, J. and D. Gilrein. 2005. Cornell Cooperative Extension of Suffolk County, LIHREC, Riverhead, NY.
• Whiteflies & Biotyping. Calabro, J. 2018. GrowerTalks Magazine.
• NC State Extension Plant Pathology Publications
• NC State Horticultural Science Publications
• North Carolina Agricultural Chemicals Manual

For assistance with a specific problem, contact your local Cooperative Extension center.