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Will water mean mosquito trouble?

City's larviciding program gears up for spring battle

By: Bartley Kives

Posted: 04/27/2011 1:00 AM | Comments: 0

Although Winnipeg has yet to see the backside of the flood of 2011, the city is already preparing for what will emerge from all the water left behind.

As early as next week, Winnipeg's Insect Control Branch may start applying pesticides to standing water in and around the city in an effort to reduce the emergence of adult mosquitoes in the coming weeks.

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While a major spring flood does not guarantee hordes of summer mosquitoes, a large amount of standing water generally means more of the insects.

Most of the water in and around the city is still flowing, and mosquito larvae cannot develop in running water. But once the water stops, Winnipeg will be left with what the Insect Control Branch calls its "maximum treatable area" -- the largest possible pool of potential larvae-development sites in Winnipeg as well as within 10 to 12 kilometres of city limits.

"Once all the ice and snow melts, the crest of the flood passes by and the water stops flowing across fields and ditches, then the spring larvicide program will likely start in the treatable maximum of 35,000 to 40,000 hectares," insect-control officials said in a statement.

The branch has started monitoring small bodies of standing water and has found little larval development. But that will change when the mercury rises. "It is expected that the larviciding program may begin next week, as daytime and evening temperatures continue to rise," the officials said.

The mosquitoes flying around Winnipeg now are adult insects that survived the winter in sewers, homes and other warm spots. It will take weeks, if not months, before they're joined by newly emerged adults.

Summer skeeter numbers may be high because of migrating mosquitoes from standing water well outside the city. But the city may begin fogging for nuisance mosquitoes one day earlier this summer. On Tuesday, Manitoba Conservation agreed to allow the Insect Control Branch to reduce the lead time to two days from three. Until this year, the city could not begin fogging for nuisance mosquitoes -- species not known to transmit disease to humans -- until more than 25 adults were caught in traps for three days straight, in at least two quadrants of Winnipeg.

In February, city entomologist Taz Stuart sent the province historical trap-count data that demonstrated two days of high mosquito counts are almost always followed by a third day of the same. That means it is pointless to wait another 24 hours to begin fogging.

Provincial licensing officials agreed. Conservation Minister Bill Blaikie wrote a letter to Mayor Sam Katz, informing him the province has agreed to change the fogging criteria.

The reduction in lead time was one of four mosquito-fogging changes the city requested last summer. One of the other requests -- to reduce the public-notification period for fogging to 24 hours from 48 -- was granted last August.

Two other city requests are outstanding. One involves more funding to allow the city to replace chemical larvicides with biological alternatives over the next two years. In the letter to Katz, Blaikie said the money won't flow until the city submits a detailed larviciding plan.

The final -- and most controversial -- city request involves reducing the size of the buffer zones around homes where residents do not want to be exposed to the mosquito-fogging agent malathion. Some Winnipeg residents believe the current 100-metre size is too large, while others oppose any reduction.

The issue has become an intergovernmental hot potato. Blaikie said the province cannot make a decision about buffer zones because the city has yet to propose a size.

St. Vital Coun. Gord Steeves said he was pleased to hear the lead time is down to two days. But he remains frustrated about the buffer zones. "I'm a bit flummoxed by my own administration with regard to this one," Steeves said. "I don't know why we can't shorten that up because of the technology we have available now."

bartley.kives@freepress.mb.ca

Republished from the Winnipeg Free Press print edition April 27, 2011 A3

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