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Florida
(Indian River)
Identification
of resistance to emergancy use pesticides.
Purpose
Field
bioassays conducted in citrus groves showed a possible decline in efficacy
of fenthion, the insecticide of choice for emergency control of the
vector Culex nigripalpus.
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Figure
1 shows map of study area.
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Background
In Florida,
Culex nigripalpus is a vector for Eastern Equine Encephalitis (EEE)
and West Nile virus (WNV). [Although most mosquito control efforts are
based on control of pest mosquitoes, it is necessary to designate an insecticide
for emergancy use.] The emergency use insecticide had been fenthion until
the data below were obtained.
Data
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Bottle
bioassays run on Culex nigripalpus from Indian River,
Florida
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Conclusions
- Indian
River populations of Culex nigripalpus were shown by CDC methods
to be resistant to fenthion.
- The mechanism
for the resistance was shown to be an elevated esterase that specifically
attacks fenthion, but not malathion.
- The organophosphates
malathion and naled were shown to be still effective for control of
the vector mosquito, as were the synthetic pyrethroids resmethrin and
permethrin.
- When
an outbreak of encephalitis cases occurred the following year in this
part of Florida, control personnel knew to use an insecticide other
than fenthion for emergency control of the Culex nigripalpus.
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