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Florida Tomato Institute Report:

‘ Q’ Biotype Whitefly: How Big a Threat?

The Tomato Magazine
December 2005

Are Florida tomato growers in for a new pest pandemic?

A new strain of ‘Q’ biotype whiteflies was discovered on poinsettias purchased at a Tucson, Ariz. retail outlet in December 2004. The finding has whitefly watchers, familiar with what happened in Florida 19 years ago, nervous about a possible repeat. The discovery is reminiscent of a scenario that led to devastating losses for Florida tomato growers, and the researchers hope that the industry can avoid an equally devastating invasion.

Phil Stansly and Cindy McKenzie addressed the threat last September during a presentation at the Florida Tomato Institute in Naples. Stansly is with the University of Florida’s Institute of Food and Agricultural Sciences in Immokalee, while McKenzie is with the U.S. Horticultural Research Laboratory, USDA-ARS, in Fort Pierce. Their presentation was entitled: “‘Q’ Biotype Whitefly: How Big a Threat?”

Discovery of the ‘Q’ biotype in Tucson was made by a team from the University of Arizona, Stansly reported. The plants were said to have been purchased from a wholesale dealer in California.

What raised major concern was the fact that, although these insects were indistinguishable in appearance from silverleaf whitefly, they proved markedly less susceptible to pyriproxyfen, buprofezin, imidacloprid, acetamiprid and thiamethoxam. Electropheresis, polymerase chain reaction (PCR) and sequencing of the mitochondrial cytochrome oxidase 1 gene revealed their unique genetic identity.

History of Whitefly Biotypes
Prior to 1986, B. tabaci, known as the sweetpotato whitefly, was thought to be pretty much the same everywhere it occurred throughout the tropics, subtropics and mild temperate regions of the world, Stansly said. Then, massive numbers suddenly turned up in greenhouse poinsettias in Florida, spreading quickly to field grown vegetables and other crops.

“ Clouds of whiteflies in tomato fields produced quantities of sooty mold and a nuisance for pickers, followed by a new plant disorder, tomato irregular ripening and a new geminivirus, Tomato Mottle,” the researcher reported. “First dubbed the ‘poinsettia’ whitefly, or even the ‘Florida’ whitefly, it came to be known as B. tabaci biotype ‘B’ to distinguish it from the former biotype ‘A.’ Biotype ‘A’ had been relatively benign in Florida but caused serious losses in California and Arizona as a cotton pest and a vector of the ‘crinivirus’ lettuce infectious yellows in lettuce and melons.”

Since the discovery of the silverleaf whitefly, numerous other biotypes of B. tabaci have been described on the basis of genetic differences at the molecular level and some biological distinctions, Stansly explained.

Likely Impact of Biotype “Q”
Will the biotype ‘Q’ whitefly eventually devastate the Florida tomato industry?

Probably not, the researchers declared. Whatever happens, the new biotype “will certainly not wreak anything like the havoc that followed the last whitefly invasion. Biotype ‘B’ rapidly overwhelmed the old “A” biotype whitefly in Florida and elsewhere with its ability to build up high populations on numerous different crops. In contrast, ‘Q’ would find itself faced with well established populations of ‘B’ on virtually any potential host plant and may not compete effectively unless assisted by insecticidal selection.”

The significance of that, according to the researchers, is ‘Q’ might not achieve a foothold in dooryard ornamentals but could in production greenhouses where a captive whitefly population might be continually exposed to a limited toolbox of products. Thus, the first control problems are most likely to appear in the greenhouse/screenhouse ornamental industry as presaged by the find in Arizona.

Whitefly samples were processed in Florida in 2001 and 2002 and sampling was resumed in 2005 after the discovery of the ‘Q’ biotype in California and Arizona. Samples have been collected and analyzed in Florida from Naples (Collier), Palm Bay (Brevard), Homestead (Dade), Parrish (Manatee), New Port Richey (Pasco), Vero Beach (Indian River), Tallahassee (Leon) and Altamonte Springs (Seminole). As of today, only the ‘B’ biotype has been detected in Florida.

Meanwhile, according to Stansly, extensive surveying in Florida tomato fields to determine if biotype ‘Q’ is present will continue. APHIS, DPI, USDA-ARS, University researchers and growers are working together in a cooperative effort.

“ The highest priority should be on sampling greenhouses and whitefly crops in proximity to greenhouses as well as retail outlets such as Home Depot,” the researcher told the group. “Knowing who and where the enemy is has always been the foundation of a good IPM program and should aide growers in making sound management decisions.”

Action Plan
So, where from here?

“Soon after discovery in Arizona, an ad hoc ‘Q’ Biotype Whitefly Taskforce was formed of interested scientists and administrators from the regulatory and research communities,” Stansly reported. “Officials from USDA-APHIS Plant Protection and Quarantine (PPQ) stated that their agency would apply the current policy for the ‘B’ biotype of the whitefly, Bemisia tabaci (‘non-reportable/non-actionable’), to the recently detected ‘Q’ biotype. Thus, there will be no specific federal barriers to movement of this pest.

“ As of yet, there has been no policy statement from Florida DACS-DPI, but it seems unlikely that movement of whitefly-infested plant material will not be regulated in Florida either. However, both agencies are cooperating in a national monitoring effort to track movement of ‘Q’ biotype. As of Oct. 26, ‘Q’ biotype has been detected in 11 states: Alabama, Arizona, California, Maryland, Georgia, Kentucky, Michigan, New York, North and South Carolina and Oregon, according to survey results summarized by USDA-APHIS. Additionally, entomologists at the Universities of Arizona and California have embarked on a program to evaluate insecticide susceptibility of the ‘Q’ biotype populations in their respective states,” Stansly said.

As movement of the new pest and associated control problems become more apparent, additional research will be directed at ways to mitigate the impact, the researcher noted. Meanwhile growers and consultants were advised to keep a sharp lookout for unusual whitefly activity and to apply even more rigorously the principles of IPM and resistance management that have served the industry so well in the past.

Mitigating the threat of biotype ‘Q’ is just one more reason to practice good IPM and resistance management practices, Stansly pointed out. He advised growers to do the following:

• Use insecticides only as needed based on scouting
• Employ alternate management strategies such as host-free periods, clean transplants and roguing of symptomatic plants
• Limit exposure of whiteflies to neonicotinoids by using them only once in tomato fields and abstaining, if possible, in other crops
• Rotate classes of insecticides.

“Sound insecticide management is our best insurance against biotype ‘Q’ and the increased threat of insecticide resistance that it represents,”
Stansly advised.

© 2006 Columbia Publishing

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