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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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