Heavy rains lead to increased mosquito populations – some tips to help control them

DATE: September 12, 2018
CONTACT: Lisa Johnson, Horticulture Educator, University of Wisconsin Extension, [email protected]; 608-224-3721 OR Andrea Diss-Torrance, DNR Invasive Forest Insects Program Coordinator, 608-264-9247

An unusual amount of rainfall in Wisconsin has resulted in lots of standing water in places that are normally dry. Unfortunately for people, mosquito larvae, sometimes called wrigglers, develop in standing water, so their populations have surged over the last few weeks.

Mosquitoes can develop in flood water but also in surprisingly small volumes of water in standing containers, abundant in our yards and neighborhoods in the form of rain barrels, fish ponds, bird baths, old tires, planters, tree cavities, gutters or anything that holds water.

To help control the outdoor mosquito population on your property, eliminate their breeding places:


  • Remove and dispose of trash that is holding water such as old tires, sagging plastic bags, or any water-holding containers.
  • Make weekly inspections of water in flower pots and plant containers for stagnant, standing water or the presence of wrigglers.
  • Change the water in bird baths and wading pools frequently. Drain them when not in use.
  • Unclog rain gutters so water doesn’t pool.
  • Drain and fill stagnant, puddles, ditches, or any wet areas around your home and property.
  • Clear weeds and vegetation away from the edges of ponds, near houses, and in nearby lots – adult mosquitoes hide in them.
  • Biological control products containing Bti, a natural mosquito larvicide, may be purchased online and at most lawn and garden stores. These products, which are usually donut-shaped or comes as pellets, are placed in standing water to kill mosquito larvae. They control mosquito larvae for up to 30 days but are harmless to people, pets, birds, fish, and other wildlife. Always follow directions on labels.
  • Cover cisterns, cesspools, septic tanks, fire barrels, rain barrels, and tubs tightly.
  • Use sand to fill in tree holes.
  • Remove tree stumps that hold water.Inside the house, keep window and porch screens in good repair. Use weather-stripping to fill gaps around windows and doors. Remember that mosquitoes also bite animals; provide pets refuge inside the house or in screened-in areas.

    If you must go outside at dawn or dusk when mosquitoes are most active, take precautions to avoid being bitten.

  • Wear long-sleeved shirts and long pants thick enough to prevent mosquito mouthparts from reaching skin.
  • Wear light tones – dark colors attract mosquitoes.
  • Use repellants on exposed skin.
  • Citronella can be helpful if the air is still.For more information, see “Mosquitoes in and Around the Home” at https://extension.entm.purdue.edu/publications/E-26/E-26.pdf


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