Rain limits disease carrying mosquitoes in St. Louis County, but increases numbers of nuisance breeds

Weather Blog

It’s that time of year again, mosquito season is in full swing. For some it may seem worse than previous years, but really, the season hasn’t been too troublesome.

“We are actually having a fairly mild season,” explains James Sayers, Vector Control Program Supervisor with St. Louis County. And the weather is to thank.

“With the amount of rain we’ve had it tends to keep catch basins and storm sewers flush, which is where the disease carrying mosquitoes tend to breed,” Sayers explains.

Those disease carrying mosquitoes are called the Culex mosquitoes, known for spreading West Nile Virus and Encephalitis. These mosquitoes are most active at dusk and dawn, and are out through the night.

The rain keeps Culex breeding grounds flushed out. However, rainy days can prove to be helpful for another type of mosquito, the nuisance mosquito.

“When we have a lot of rainfall that makes it worse for your nuisance mosquitoes, that tend to breed in woodland pools, standing water, and fields. These are the areas that don’t get flushed they just get more water,” says Sayers.

Nuisance mosquitoes are also known as the daytime mosquitoes; these can be seen at all hours: morning, afternoon, and night. These mosquitoes also bite, but St. Louis County Vector Control isn’t overly concerned since they aren’t typically disease transmitters.  

Along with rain, the summer’s heat can also play a role.

“When we have warmer temperatures that basically effects the mosquito lifecycle. The warmer temperatures allows them to go from an egg, to a larvae, to a pupa, to an adult faster.”

Even with a mild season, mosquito activity can be largely dependent on location. If you are closer to standing water, you may see an uptick in activity. Iit is important to check property for standing water in your yard, along with gutters, bird baths, buckets, and flowerpots.

St. Louis County is checking in on the mosquitoes across the county with 240 trap sites. Vector control has seen a relatively low number of complaints. Cases for West Nile Virus in mosquitoes have been below average.

St. Louis County has seen one human noninvasive West Nile Virus case.

In addition to location, mosquito bites can be largely dependent on the person.

“Different people have different biological makeups, so it is true,” Sayers explains. “Some people are more prone to being bitten.”

That’s why it’s important to remember your bug repellent and limit your activity outdoors, especially during dusk and dawn.

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