Sept. 20, 2011, 11:01 a.m.
The looming disappearance of Edmonton’s main anti-mosquito chemical could make the swatting season worse in the future, a city expert says.JIM GATHANY, AFP/GETTY IMAGES, FILE City council is searching for the best way to control the mosquito population now that an effective chemical isn’t available.
The best product for mosquito control is Dursban, but the manufacturer has stopped making the product and it won’t be available in Canada after 2014, biological sciences technician Mike Jenkins said Monday.
The current substitute requires more applications under stricter weather conditions, he said.
“Without having the Dursban, we’re going to have a less-effective (control) program. We have a narrower window of opportunity to treat the larvae,” he said, adding the city could have to scrap spring spraying if it isn’t effective.
“Potentially, it could have a very large impact on the number of mosquitoes, not only the number we see biting in the spring, but going into the summer (as they reproduce).”
This year’s heavy snow and rainy spring led to mosquito numbers that haven’t been seen for decades.
If these conditions continue, there could only be enough Dursban left in the city’s stockpile for one more year, although Jenkins said the product will be saved for times when it’s most needed.
“If we get some dry years, it could last a long time. If we get wet years like last year, it may go sooner,” he said.
“The alternatives are not very effective at cold temperatures, so they’re not as effective used in the spring.”
Although Winnipeg — the only other North American city using Dursban — has looked at switching to other products, officials there decided they needed it, Jenkins said.
Parks branch manager Lyall Brenneis said the other product used in Edmonton, Vectobac, sinks to the bottom of watery ditches and gullies in a day, while Dursban stays active at least two weeks.
The need for repeated applications and other factors will make relying on alternatives more expensive, he said.
“If we go to a product line where we have to spray with Vectobac repeatedly … we will have to assess whether there’s merit in trying to run a spring campaign.”
That could mean far more mosquitoes in Edmonton: traps in surrounding municipalities that don’t spray catch on average five times more of the pests than inside the control area, which stretches outside city boundaries.
However, staff is looking for different products that might do a better job, Brenneis said.
Council’s community services committee asked staff to prepare a cost estimate for boosting the amount of helicopter spraying by up to 60 per cent in 2012. That proposal will be discussed during this fall’s city budget debate.