Description

Adult Description: Even though this species is called a whitefly Bemisia argentifolii is not a Dipteran (fly) insect. The silverleaf whitefly is a small plant-feeding insects with piercing-sucking mouthparts, and both immature and adult whiteflies feed on the undersides of leaves. This yellow-greenish bodied moth-like insect grows to about .8mm and has snow-white wings because of wax secretions on its body and wings. The white wings fold over the bodies while at rest.

Larval Description: Whitefly eggs are ovoid and have a peg-like pedicel that is inserted into a slit made by the female’s ovipositor in the leaf surface. The pest goes through four nymphal instars, ranging from about .3 mm as first instars (crawlers), to .6 mm as fourth instars. The immature stages are thin, flat, elliptical and greenish-yellow.

Host Plant: Bemisia argentifolii has been reported on an estimated 500 plants worldwide. Favorite hosts include melons, tomatoes, eggplants, peanuts, broccoli, cabbage, cotton, squash and a number of ornamental (e.g., poinsettia) and native plant species.

Ecological Threat

Feeding whiteflies extract important plant nutrients, causing defoliation, stunting and poor yield. Sticky honeydew is excreted by whitefly nymphs and adults, promoting the growth of black sooty mold on leaves. The mold renders cotton difficult to process and requires washing of vegetables, thus increasing production costs. SLW also causes several plant physiological disorders, including tomato irregular ripening and squash silverleaf. Bemisia argentifolii can vector several viral plant diseases. It is believed that the pest injects foreign enzymes into the host plant while feeding, affecting the normal physiological processes.

Biology

Most whitefly species are arrhenotokous, and females are produced from fertilized eggs. Males are haploid and come from unfertilized eggs. The ratio of male and female whiteflies in a population changes over time and is affected by both temperature and male longevity. Males tend to live for shorter periods and populations appear female biased as a result. Females average about 160 eggs each. First instar nymphs which hatch from eggs are mobile, and walk a short distance before selecting sites where they settle to commence feeding. Once a feeding site is selected the nymphs do not move.

History

Bemisia tabaci was first discovered on poinsettia crops in Florida; it quickly moved into other southern states with intensive agricultural and horticultural industries (Texas, Arizona, and California), and displaced the original Bemisia tabaci (A biotype), which can no longer be found in the United States. The B biotype was described in 1994 as a new species, Bemisia argentifolii. Its common name is the silverleaf whitefly, because of its unique ability to induced silverleaf disorder in squash.

Native Origin

India or the Middle East

Current Location

U.S. Habitat: Bemisia argentifolii occurs around the world in tropical and subtropical areas and in greenhouses in temperate areas. It is a major pest of greenhouses in the United States.

Distribution

U.S. Present: AZ, CA, FL, GA, HI, LA, NC, NM, and TX

Resembles

The silverleaf whitefly can be confused with other insects such as the common fruitfly but with close inspection, the whitefly is slightly smaller and has a distinct wing color that helps to differentiate it from other insects.

Management

Thankfully there are several biological control strategies (predator, parasitoid and pathogens) that can be used and are successful on managing some silverleaf whitefly populations.

At least four species of predators that are commercially available have been evaluated for their ability to control Bremisia tabaci on greenhouse grown crops: Delphastus pusillus, Macrolophus caliginosus, Chrysoperla carnea, and C. rufilabris. Each species is able to affect whitefly populations at different life-cycle stages. Some studies have shown that D. pusillus combined with E. luteola at a weekly release rate of one beetle and one parasitoid per plant can control B. tabaci strain B to levels attained with insecticides. The main parasitoid of Bremisia tabaci is a Hymenopteran insect, Eretmocerus eremicus. There is another species of hymenoptera but it is not successful on Bremisia tabaci. There are also several kinds of fungal pathogens known to kill whiteflies and three are commercially available; Paecilomyces fumosoroseus, Verticillium lecanii and Beauveria bassiana.

Overall, what studies have suggested a combination of predators, parasitoids, pathogens and insecticides it the best management strategy to control whitefly populations.

References

Barinaga, M. 1993. Is Devastating Whitefly Invader Really a New Species? Science. 259: 30.

Bellows TS Jr, Perring T M, Gill RJ, Headrick DH. 1994. Description of a species of Bemisia (Homoptera: Aleyrodidae). Annals of the Entomological Society of America 87: 195-206.

Perring, T. M., A. D. Cooper, R. J. Rodriguez, C. A. Farrar, and T. S. Bellows Jr. 1993a. Identification of a Whitefly Species by Genomic and Behavioral Studies. Science. 259: 74-76.

Perring, T. M., C. A. Farrar, T. S. Bellows, A. D. Cooper, and R. J. Rodriguez. 1993b. Evidence for a New Species of Whitefly: UCR Findings and Implications. California. Agric. 47: 7-8.

Xu, J., De Barro, P. J., & Liu, S. S. 2010. Reproductive incompatibility among genetic groups of Bemisia tabaci supports the proposition that the whitefly is a cryptic species complex. Bulletin of Entomological Research, 100(3):359.

Internet Sources

http://cisr.ucr.edu/silverleaf_whitefly.html

http://www.biocontrol.entomology.cornell.edu/parasitoids/eretmocerus.html

http://biocontrol.ucr.edu/bemisia.html

http://edis.ifas.ufl.edu/pdffiles/IN/IN00400.pdf

https://insects.tamu.edu/fieldguide/aimg97.html

http://extension.umass.edu/floriculture/fact-sheets/biological-control-growers-guide-using-biological-control-silverleaf-whitefly

http://www.biotech-system.com.ua/en/production/entomophages-and-acariphages/macrolophus-caliginosus/

http://www.moldbacteria.com/mold/paecilomyces.html

http://www.drrajanlaboratories.com/product7.html

http://www.uoguelph.ca/~gbarron/MISCELLANEOUS/nov01.htm

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