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Control
project keeping mosquito population in check
By Jeffrey
Pickette
Citizen Staff
Mosquitoes
are the unequivocal summer pest — always ready to suck the fun
out of those much-anticipated outdoor barbeques, camping
excursions, or trips to the beach.
This season,
however, the population of “reflood mosquitoes” is less
prevalent in Canton than in previous years, according to John J.
Smith, director of the Norfolk County Mosquito Control Project.
Reflood mosquitoes, which are the species that typically bite
humans, emerge in large numbers after heavy rain events.
With a lack
of significant rainfall to date this month, there has not been
enough precipitation to flood the Neponset River flood plain,
which in turn has kept the reflood mosquito population in check.
“These
species also act as a bridge vector,” said Smith, explaining
that “it moves certain viruses like EEE (Eastern Equine
Encephalitis) and West Nile Virus between birds and humans, so
it’s good that those species are low this year.”
Still, it is
not guaranteed that this trend will continue for Canton and the
other towns across Norfolk County. A series of heavy rainstorms
or a tropical weather pattern could change the course of the
summer and bring about a drastic increase in reflood mosquitoes.
“The
potential of it becoming a nuisance, or possibly even a public
health threat, is always there,” said John Ciccotelli, Canton’s
public health director. “It really all depends on the weather.
If we get rain and it continues for the next month off and on so
that things stay wet — because [mosquitoes] like wet — then it
could explode into a bad situation.
“Currently,
though, if the weather conditions stay the same, we’ll probably
have an easy summer as far as mosquitoes are concerned.”
The Norfolk
County Mosquito Control Project aims to deal with the mosquito
population while in the larval state, before it has matured to
adult status.
This past
April, the Mosquito Control Project conducted initial ground and
aerial missions targeted to decrease the number of mosquito
larvae in low-lying swampy areas or wetlands throughout the
county, like the Neponset River.
A granular
form of Bti (Bacillus thuringiensis israelensis), the spore form
of a naturally occurring soil bacteria, is eventually ingested
by the larvae and then releases toxins within the larvae itself.
If a heavy rainstorm impacted the region, the process would be
repeated to prevent the re-growth of additional larvae, so long
as there was enough funding in the budget to conduct this costly
project.
“We won’t
get all of them,” Smith said, “but we have had upwards of 80 to
100 percent control in areas we have been monitoring. If I got
80 percent or higher, I’d be very happy.”
Since some
of the larvae survive and become adult mosquitoes, the Norfolk
County Mosquito Control Project conducts early morning ULV
(ultra low volume) aerosol applications throughout the county
starting in late May.
Canton is
sprayed from 2 a.m. to 5 a.m. every Wednesday from May through
September in an effort to control the adult mosquito population.
The product is sprayed from the back of a truck and diffuses in
the air, depending on which direction the wind is blowing. The
mosquitoes fly through the mist and droplets of “adulticide”
will fall on the mosquito and kill it.
Even though
Smith considers adult mosquitoes to be “fragile insects,” it can
be difficult for the product to reach a mosquito. With a number
of variables at play, Smith considers a 50 percent extinction
rate for the aerosol application a success.
“The
adulticide is what we would call a last-ditch effort to try to
control,” he said. “It’s not as effective as the Bti
application. We prefer to do the larval control because we can
target [mosquitoes] away from residential areas.”
While
residents have the right to refuse to have their property
sprayed with the adulticide, Smith, Ciccotelli, as well as the
Environmental Protection Agency, consider both the aerosol and
Bti to be environmentally safe.
Ciccotelli,
who has conducted his own research on the adulticide chemicals,
has found “no effect to humans in the doses they are using and
in the concentrations they are using.” Still, if residents wish
to not have their property sprayed, they can contact the Norfolk
County Mosquito Control Project at 781-762-3681.
As for Bti,
Ciccotelli is equally supportive of its use. “You could eat it
if you want to,” he said. “I don’t know anyone who would want
to, but it would be completely safe to humans and any other
species.”
While the
reflood mosquito population may be at a low level, Smith said he
has seen an increase in “Culex” mosquitoes — container breeders
that can transmit the West Nile Virus. Although they do not harm
humans early in the season, they tend to bite them later in the
summer. Culex mosquitoes are more prevalent in the eastern part
of the county in urban communities.
“These
numbers are high above their average for the trap sites,” Smith
said. “We are a little concerned about those mosquitoes. They’re
not real heavy human biters, but they have been implicated in
transmitting West Nile Virus, so we’re keeping a close eye on
them.”
While people
can prevent contact with mosquitoes by wearing long sleeves and
pants in wooded areas, applying bug repellants, and avoiding
spending time outdoors at dawn or at dusk, both Smith and
Ciccotelli stressed the importance of avoiding the build-up of
standing water on residential properties, whether it be in
child-size pools, bird baths, or other containers full of water.
“It’s very
important for people to be policing their properties and looking
for anything that will hold water and eliminating these
above-ground breeding areas,” Smith said.
For more
information, contact either the Board of Health at 781-821-5021
or the Norfolk County Mosquito Control Project.
July 24, 2008
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