Pest-management crews in Regina are treating pools of water with bacteria that attack mosquito larvae. (CBC)

Saskatchewan's summertime preoccupation with mosquito counts has begun, as pest control experts say the insects have already made an appearance in the province despite an unusually dry and frigid start to the season.

Health officials take the monitoring effort seriously, as one species common to the prairies — Culex tarsalis — can transmit the West Nile virus.

In Regina, city pest-control crews began treating pools of standing water with larvicide three weeks ago.

"The product is specific to mosquito and biting-fly larvae," Wade Morrow, from the city's pest management branch, told CBC News. "So it's not going to be harmful to dragonfly larvae that are in the water, frogs or other things, birds or other things that are out here. It's not harmful to them."

Morrow said Regina's mosquito-population estimates are lower than average for this time of year.

So far, Culex tarsalis has not made an appearance in traps.

"We actually had our first batch of mosquitoes out on the weekend, but they're not the kind who carry West Nile virus," Phil Curry, a disease prevention consultant for the provincial Health Ministry, told CBC News. "The one that carries West Nile virus will just keep building up its population as we start to get hotter and hotter weather."

Curry said the first generation of mosquitoes that could transmit West Nile virus will likely not be seen until mid-June. The species is most active in July and August, especially if there are above-average temperatures.

"Environment Canada keeps telling us we're supposed to get above-normal temperatures in June and July," Curry noted. "So if that happens, we will see higher numbers of Culex tarsalis and higher numbers of virus."

Larviciding will continue in Regina until the end of the September. Officials said they may have to perform multiple applications to some sites. The product used is an environmentally friendly bacteria, they said.