ST. LOUIS COUNTY, Mo. – This summer’s weather conditions have been ideal for an increase in mosquito populations. St. Louis County Public Health Vector-Borne Disease Prevention employees are actively working to control mosquito numbers.

“You know, with the spring rains, we are anticipating a pretty heavy mosquito season this year,” James Sayer, supervisor of the St. Louis County Department of Health’s Vector Control Center, said. They have been working diligently over the last six weeks to put larvicide in standing water all around the county.

“We typically try to get out and pretreat all the flood prone areas before the spring rains so that we try to get a handle on mosquitos before they get bad,” Sayer said.

Hot and dry conditions are typically when we see the most West Nile virus cases, but humidity doesn’t hurt.

A two-pronged approach is used to try to control the problem. They get the biggest bang for their buck by using larvicide, which is the control of larval mosquitoes. They also do adult spraying with their trucks. The time at which they spray depends on what type of mosquitoes they are trying to eliminate.

Recent heavy rains in April and for the start of May are normally not a good thing for emerging mosquito numbers. But sometimes, it can be.

“We tend to focus our control activities more on the types of mosquitoes that transmit diseases and make you sick. Those types of mosquitoes tend to be more prevalent in storm sewers and catch-basins,” Sayer said. “So, when we get frequent rains, it tends to flush mosquito larvae out and kill them. On the other hand, those frequent rains can also tend to flush out our larvicides.”

Of course, the best way to protect yourself from West Nile virus is to protect yourself from mosquito bites.

“Long sleeves, long pants, light colors. Limit time outside during dawn and dusk and wear mosquito repellents that are EPA approved,” Sayer said.

To further reduce your property’s attractiveness to mosquitos, rid yourself of any standing water on or near the property. This includes items that can hold water, like buckets, children’s toys, kiddie pools, clogged gutters, or French drains.

Vector-Borne Disease Prevention spray schedule – St. Louis County

CDC tips to control mosquito populations around your home

Remove standing water where mosquitoes lay eggs

  • Once a week, empty and scrub, turn over, cover, or throw out any items that hold water like tires, buckets, planters, toys, pools, birdbaths, flowerpot saucers, or trash containers. Mosquitoes lay eggs near water.
  • Tightly cover water storage containers (buckets, cisterns, rain barrels) so mosquitoes cannot get inside to lay eggs.
  • For containers without lids, use wire mesh with holes smaller than an adult mosquito.
  • Fill tree holes to prevent them from filling with water.
  • Repair cracks or gaps in your septic tank if you have one. Cover open vent or plumbing pipes. Use wire mesh with holes smaller than an adult mosquito.

Kill mosquito larvae outside your home

  • Use larvicides to treat large bodies of water that will not be used for drinking and cannot be covered or dumped out.
  • When using larvicides, always follow label instructions.

Drain and turn over kiddie pools.

Kill mosquitoes outside your home

  • Use an outdoor adulticide to kill adult mosquitoes in areas where they rest.
  • Mosquitoes rest in dark, humid areas like under patio furniture or under the carport or garage.