Data on mosquito trends tells us to get the bug spray ready

An arid spring has kept the number of mosquitoes in Minnesota down this summer, but don't put away the bug spray just yet.

Recent downpours in parts of the Twin Cities have caused a sizable new crop of skeeters to hatch.
That's the latest buzz from the experts at the Metropolitan Mosquito Control District, a government agency that tracks the number of mosquitoes across the seven-county metro.

"Rainfall is the biggest factor," said Mike McLean, the MMCD's communications director.

District staff also are responsible for treating affected areas to control the mosquito population. There are more than 50 different mosquito species in the state, but the type that people are most likely to swat at this time of year is the summer Aedes, he said.

More pest than disease-carrier, this type is heavily dependent on rain for its survival, and it can spawn several generations throughout the summer. Adult mosquitoes of this type can live up to two weeks.

Frequent or heavy rains cause water to pool on the ground, creating an ideal surface for the mosquito to lay its eggs. Lots of eggs. It takes about a week and a half after the rain stops for the eggs to hatch.

The result: an uptick in bloodsuckers. In general, the northern parts of Anoka, Hennepin, Washington and Ramsey Counties tend to have more mosquitoes than the rest of the metro, according to the MMCD, which maintains data-collecting sites scattered across the metro.

"Last week's heavy rains did cause a hatch," said Stephen Manweiler, the MMCD's executive director. "It had been so dry before the rain that a lot of the sites didn't flood up as much as they usually would. We got a medium sized hatch out of it."

Despite the dry conditions in May and June, if the rains keeps falling in July, the mosquito numbers may balloon — just as they did at this time last year.

"Last year, starting by mid-July, we had perfect storms every week. We had big, major hatches every week," Manweiler said.

So far, this summer's rainfall and mosquito numbers resemble last year's late-bloomer pattern.

"Last year started out slow and this year started out slow," he said. "It was just about now that things started to pick up last year," he said.

To find out if wet areas near you have been treated to control mosquito larvae, use the MMCD's interactive map.

If you'd like to see more data from the MMCD, check out their annual operational reviews.

Data Drop is a weekly feature that uses data analysis and visualizations to explain, surprise, inform and entertain readers on topics relevant to Minnesotans. Do you have an idea you'd like us to explore? Contact MaryJo Webster