Mosquitoes to return to Calgary thanks to wet weather

CALGARY – After a two-year mosquito holiday, we are going to get our fair share of the biting bugs this summer — thanks to the recent rain.

Simon Wilkins, the city’s integrated pest management co-ordinator, said this wet weather, combined with some hot summer sun, will create perfect conditions for the nasty insects to flourish.

"It’s not like there’s a catastrophe on the horizon, but we are expecting a normal level of mosquitoes this year," said Wilkins.

He noted the past two summers have been virtually mosquito-free because of dry conditions. The bugs need a wet breeding habitat combined with heat to flourish.

"Eggs can lie dormant in soil for several years," said Wilkins. "That’s what happened in the 2005 flood. Areas of the city got hit with water that normally don’t have water and then all the eggs hatched and it led to a higher number of mosquitoes in 2005 and 2006."

There are some mosquitoes around Calgary now, but they’re missing a key component: sunshine.

"They’re out there in the cold and wind and slowly developing. If the weather warms up, people will see them."

Water and heat combine to make a perfect home to raise a mosquito — millions of them.

"Adults lay eggs and then they hatch. Four days later, you have an adult. When you have a lot of mosquitoes, it can be because generations hatch all around the same time. It’s like your great-great-grandfather and great grandfather are still alive at the same time as the grandchildren."

Calgary’s mosquito control program samples areas around the city, as well as outside it during bug season.

"One thing people don’t know is mosquitoes don’t start in the city. They hatch and fly in," said Wilkins. "Typically, the east is the major source of mosquitoes. There are lots of ditches and farms. That tends to be a large area for habitat."

City backyards can also make good breeding grounds for the flying bloodsuckers.

"The concern that exists there is if people have things in their yard like bird baths, old tires and kiddie pools," Wilkins said. "They leave them out all summer, and it’s standing water. Don’t have standing water in your yard."

It’s in these warm still pools that mosquitoes like to lay eggs. There are about two dozen types of mosquitoes in Calgary, and Wilkins said the bugs out now aren’t responsible for West Nile.

"The ones that carry West Nile come out at the end of July and in August."

Dr. Andre Corriveau, Alberta’s chief medical officer, noted the province had two cases of West Nile virus last year, one in 2008 and 320 cases in 2007.

"We’ve had two years of very low numbers, but it’s the nature of the infectious diseases to go in cycles," said Corriveau.

He said a wet spring followed by warm weather could make for a good mosquito season. He noted the type of mosquito that spreads West Nile prefers to bite birds in the corvid family, including crows, ravens and blue jays. The first signs of the virus will show up in these dead birds.

"They’re part of the sentinel system in the community. It’s really the first clue."

lstorry@theherald.canwest.com