To spray or not to spray? Towns rule out Bti for bloodsuckers

To spray or not to spray?
Towns rule out Bti for bloodsuckers


Mrs. Mosquito goes shopping for the kids. Different species mean there’s always a demand for blood as long as there are breeding areas in the form of standing water.

by Julie Cadieux

The municipalities of Hudson and St. Lazare are not considering spraying for mosquitoes and blackflies even though this past month’s record rainfall and flooding are creating winning conditions for the bloodsuckers.
The Town of Senneville is the latest Montreal-area municipality to begin spraying Bacillus thuringiensis subspecies israelensis (Bti), a naturally occurring soil bacterium that produces a protein crystal toxic to mosquito and blackfly larvae.
At the June 7 St. Lazare town council meeting, a resident expressed frustration over the mosquitoes but mayor Pierre Kary replied that there were no current studies or plans in place to spray for mosquitoes this year.
Meanwhile, the Town of Hudson’s Environment committee unanimously recommended against a pilot project using Bti, based on data from entomologist Dr. Christopher Buddle and Jennifer Dumoulin, the town’s new environmental officer.
“BT is a reasonable choice for mosquito control under certain conditions, but in my opinion, these conditions do not apply to Hudson,” Buddle said via e-mail.
“More specifically, mosquitoes are merely a nuisance here (i.e., West Nile threat is past, we are not an ‘urban’ centre, our mosquitoes are not very bad compared to, for example, the entire boreal forest of Canada, Winnipeg, or the Tundra); they are important food for highly valued wildlife (e.g, frogs, fish, bats, etc.) and are part of the food webs within our wild lands.
As well, Buddle doesn’t think that applying Bti would be feasible in a town like Hudson given the vast amounts of wetland habitat, much of it not easily accessed.
“Finally, this spray is not just specific to mosquitoes – it affects other ‘non-target’ flies,” he added.
Dumoulin notes that the town would have to get an exemption from its own pesticide bylaw in order to apply Bti, and then only by being able to prove there’s a danger from the infestation. “If we had a West Nile problem, we might consider it more seriously,” she said.
Both agreed that mosquitoes are a part of Hudson.
“People who do not like mosquitoes can either wear appropriate clothes, sit in a screened-in porch, use repellent-type sprays, or move somewhere else,” said Buddle.
“We can’t have it all ways…part of the pleasure of Hudson is that it is relatively forested, and has swamps, lakes and streams. This is part of its charm, but comes at the cost of having to live with the wildlife….even those that like to bother us.”
According to Dr. David Lewis, of the Department of Natural Resource Sciences at McGill University’s MacDonald Campus in Ste. Anne de Bellevue, we could have a bumper season for mosquitoes and blackflies.
He explains that our region has two varieties of mosquitoes, one that has a long life cycle of one generation per season, making it possible for next spring to be a bumper year as well. The second variety has two or three generations per season and if the right wet conditions keep up then we could see an increase later on this summer. However Dr. Lewis noted that just a few days of hot sun will dry up pools of standing water, killing off the larvae and making it difficult for existing mosquitoes to lay their eggs.
Used worldwide since 1982, Bti apparently does not affect other insects, birds, fish or mammals and biodegrades quickly with exposure to sunlight and microorganisms.
In studies when Bti spores were ingested or inhaled they were eliminated without any health effects. For these reasons it has become a preferred biological control mechanism in densely inhabited areas.
Still, residents are split over whether to spray or not to spray. “Why take any chances?” says Joanne Ménard, mother of two. “The mosquitoes are a pain for a few weeks but that’s part of living in a beautiful natural environment.”
Not everyone shares that attitude. “I have to spray myself with bug spray so that I don’t get bitten. I bet that’s way more dangerous that Bti,” complained another resident.— with files from Jim Duff

The Hudson St. Lazare Gazette – June 15 2011


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