Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2010
Publication Date: 12/1/2010
Citation: Dennehy,T.J., Degain,B.A., Harphold,V.S., Zaborac,M., Morin,S., Fabrick,J.A., Nichols, R.L., Brown, J.K., Byrne, F.J., Li, X. 2010. Extraordinary resistance to insecticides reveals exotic Q biotype of Bemisia tabaci. Journal of Economic Entomology. 103(6):2174-2186. Interpretive Summary: The sweetpotato whitefly Bemisia tabaci is a severe pest of cotton, vegetables, melons, tomatoes, and other crops grown worldwide. Historically, invasions by exotic B. tabaci biotypes with increased levels of insecticide resistance have resulted in severe crop losses and disruption of management practices. The Q biotype of B. tabaci has been associated with severe resistance problems in several parts of the world, but not previously identified in the New World. Here we report that during routine resistance monitoring in Arizona in 2004, a strain of B. tabaci from ornamental poinsettias was found with unusually high levels of resistance to a wide range of insecticides and was confirmed as the Q biotype. Although this is the first report of Q biotype in the U.S., collections of B. tabaci from cotton, vegetable, and melon fields from 2001-2005 did not reveal its establishment yet in field systems in Arizona.
Technical Abstract: The whitefly Bemisia tabaci (Gennadius) possessing unusually high levels of resistance to a wide range of insecticides were discovered in 2004 in the course of routine resistance monitoring in Arizona. The multiply-resistant insects, collected from poinsettia (Euphorbia pulcherrima) plants purchased at a retail store in Tucson, were subjected to biotype analysis in three laboratories. Polyacrylamide gel electrophoresis (PAGE) of naphthyl esterases and sequencing of the mitochondrial cytochrome oxidase I gene (780 bp) confirmed the first detection of the Q biotype of Bemisia tabaci in the New World. This U.S. Q biotype strain, referred to as Poinsettia’04, was highly resistant to two selective insect growth regulators, pyriproxyfen and buprofezin, and to mixtures of fenpropathrin and acephate. It was also unusually low in susceptibility to the neonicotinoid insecticides, imidacloprid, acetamiprid, and thiamethoxam, relative to B biotype whiteflies. In 100 collections of whiteflies made in Arizona cotton (Gossypium spp.), vegetable, and melon (Cucumis melo) fields from 2001 through 2005, no Q biotypes were detected. Regions of the U.S. that were severely impacted by the introduction of the B biotype of B. tabaci in the 1980s would be well advised to promote measures that limit movement of the Q biotype from controlled environments into field systems and to formulate alternatives for managing this multiply-resistant biotype, in the event that it becomes more widely distributed.