Drought is driving down the total number of mosquitoes around Regina. Here's why that could be a problem

The dry conditions in the southern part of the province are making way for more disease-carrying mosquitoes.

Culex tarsalis, the notorious disease-carrying mosquito, thrives in dry conditions. They were in higher numbers last year than the five year average and made up a "significant proportion of the mosquito population during July and August," according to the province. 

It has been very dry, but the dry conditions still mean less mosquitoes in general.

Nuisance mosquitoes like hot and wet conditions, because that's when they lay their eggs in standing water. Those mosquitoes are lying low due to the lack of moisture, while disease carriers are enjoying ideal conditions.

There are 12 mosquito traps within the city of Regina. So far, they have caught two mosquitoes in total over the three weeks the city has monitored the traps.

"Hot and wet: lots of mosquitoes. Hot and dry: not so many mosquitoes," entomologist Taz Stuart emphasized. "So that's where people stop taking those personal protection measures to protect themselves from the bad mosquitoes that might be out there."

West Nile Virus was also detected in mosquitoes for the first time in the Prince Albert, which was the northern most pool of mosquitoes, the province noted. A report says the find, "may indicate a broadening range for the Culex species in Saskatchewan." That could be due to a shift in the climate in northern Sask.

That area has seen a shift toward more rainfall rather than snowfall, according to Terri Lang, warning preparedness meteorology for Environment Canada.

There were also more of those mosquitoes recorded at night last year in southern Saskatchewan than in previous years. There were about 101 C. tarsalis mosquitoes recorded in 2018.

The 10 year average for this time of year is about 29 mosquitoes throughout the city's traps, dating back to 2009. Going back to 1986, the average in Regina is 46 mosquitoes per trap but it's still early. The mosquito numbers tend to ramp up in late June.

"Warm and dry weather in May accelerated C. tarsalis biting, egg-laying, and larval development. Mean monthly temperatures were 3-4° C above normal in May," the province noted. 

Dry conditions likely to continue

The last two years have been particularly dry, Lang notes.

"Most places are running a fairly significant deficit of moisture," she said.

The last two years are sort of a microcosm of what has been happening in the long-term, as the average temperature has warmed by about 1.7 C since 1948 in Canada, Lang said. That warming has been more intense over the arctic and the prairies as well and the greatest warming has been happening during the winter months. When winter warms earlier, it means the snow is melting earlier and also drying up earlier. 

The 30-year average for precipitation in the area is about 95.2 millimetres. So far, there has been about 23.8 mm this year before the weekend rainfall. There was 51.5 mm of it last year and  31.5 mm in 2017. There was about 8.5 mm of rain on Saturday, but the seven-day forecast shows more dry conditions possibly to come.

It's not just Regina either. Saskatoon, Swift Current and surrounding areas have also had less moisture than the 30-year average in those parts of the province.

Saskatoon's 30-year average is 81.3 mm of precipitation. They had 58.8 mm last year and that's down from 76 mm the year before. Swift Current's 30 year average is 86.4 mm of precipitation but that area received 53.2 mm last year and 42.4 mm in 2017, according to Lang.

"The duration of snow cover has been noticed to be decreasing in time. So, they expect that trend to continue. That means significant reductions in seasonal snowfall accumulation across southern Canada," she said. 

"That has an effect on freshwater availability as well. Because if there's not as much snow cover, that'll affect how much freshwater is available and if things start melting earlier that has an effect on when waters will peak."

So, less standing water for mosquitoes to breed but also less moisture for farmers crops too. When it is as dry and hot as it is, Stuart said mosquitoes — like people — will seek out shade and wait until it's cooler to go out. 

Stuart said the only mosquitoes that suck blood are the females, who only suck the blood after breeding. Once they've bred in a mosquito swarm, they're out for blood. They don't die after blood meals either; they can go for another round or two.

"But over these past three four years it's been very, very reduced so people become complacent," Stuart said. "And it's important to use personal protection measures to protect ourselves from mosquito bites."