The Tomato Magazine
Florida Industry Remains on Alert for Silverleaf Whitefly
Although biotype Q of the sweetpotato whitefly has not been found in
any Florida tomato fi elds, it represents a new threat to vegetables and
other crops in Florida.
Speaking Sept. 6 during the Florida Tomato Institute in Naples, Fla.,
David J. Schuster said biotype Q has been found in greenhouses and nurseries
in 22 states, including Florida.
The concern, of course, is that it eventually will spread into tomato
fields. Biotype Q is the most prevalent sweetpotato whitefly biotype in
the Mediterranean region, he reported, and has plagued greenhouse-grown
crops in southern Spain for years. This biotype is resistant to many of
the commonly used insecticides for managing whitefl ies, including the
pyrethroids, neonicotinoids, pymetrozine and insect growth regulators.
On top of that, resistance to biotype Q is more stable than that in biotype
B, the key pest of tomatoes in southern Florida. Resistance does not diminish
A resistance management working group was formed in 2003 to promote
resistance management on a regional basis, Schuster said. The
group modified previous resistance management recommendations and met
with growers to encourage their adoption. The working group consisted
of University of Florida research and extension personnel, representatives
of the chemical companies marketing neonicotinoid insecticides, representatives
of commodity organizations and commercial scouts.
Because of the threat of biotype Q and decreased insecticide susceptibility,
the group was expanded and met in May, 2006, to once again discuss and
revise the whitefl y and resistance management recommendations. From those
discussions, field hygiene and cultural practices were identified as being
a high priority and should be included as an integral part of the overall
strategy for managing whitefly populations, Tomato yellow leaf curl virus
(TYLCV) incidence and insecticide resistance.
These practices will help reduce the onset of the initial infestation
of whitefly and lower the initial infestation level during the cropping
period, thus reducing insecticide use and selection pressure for insecticide
resistance development, the researcher said. The recommendations
also include insecticide use recommendations which help improve whitefl
y and resistance management.
Mandatory Burndown Rule
One outcome of the whitefl y, virus and resistance management discussions
has been the proposal of a mandatory Tomato Plant Destruction
rule by the Florida Department of Agriculture and Consumer Services, Schuster
told the group. The proposed rule was coordinated by the Florida Tomato
Committee and mandates that, within five days following final harvest
of a tomato crop, commercial tomato producers destroy remaining
tomato plants on the production site.
They are to use chemical burn-down with a contact desiccant-type herbicide
that is EPA labeled and approved for this use, he explained. An example
of an approved product would be paraquat. The herbicide should be combined
with a minimum three percent oil and a non-ionic adjuvant to enhance destruction
of the crop as well as to reduce the number of whitefl ies present which
could migrate to nearby crops. Crop destruction must be followed by immediate
complete destruction by crop removal unless double cropping is planned.
The proposed rule also contains a provision providing for enforcement,
the speaker said.
This proposed rule is agreeable to most growers and is the first
attempt to manage the whitefly/virus situation in tomatoes by regulatory
enforcement, Schuster said.
Some growers support defined, mandatory crop-free periods in the
summer while others do not. If progress is not made in the management
of the silverleaf whitefl y and associated TYLCV, pressure may build for
a regulatory rule stipulating crop destruct and crop planting dates.
© 2006 Columbia
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