Some species of mosquitoes are able to transmit diseases to humans. Female mosquitoes feed on the blood of humans and other animals.

If a mosquito is infected with a disease like West Nile virus, there is a potential that they spread that disease to the animals they feed on.

Reduce Mosquitoes

Mosquitoes reproduce by laying eggs on standing water, and they can develop in any standing water that lasts more than 4 days. Even a small bucket can become home to up to 1,000 mosquitoes!

To reduce the number of mosquitoes around your home, eliminate places where mosquitoes breed:

  • Keep all buckets and cans of water empty and change the water in wading pools every other day.
  • Keep swimming pools maintained by proper chlorination and working equipment.
  • Keep rain gutters cleared of debris.
  • Keep vegetation in and around ornamental ponds thinned.
  • Consider adding a water feature to your pond since immature mosquitoes cannot breathe in moving water.
  • Make sure rain barrels are designed so mosquitoes cannot enter.
  • Talk to with neighbors about mosquito prevention tips.

Learn more about preventing mosquitoes at home»

Prevent Mosquito Bites

  • Install or repair all window and door screens.
  • Consider staying indoors during peak mosquito biting times, from dusk to dawn.
  • Wear long-sleeved clothing and long pants whenever you are outdoors.
  • Avoid perfumes and colognes when outdoors for long periods of time.
  • Use a mosquito repellent containing 20 to 30 percent DEET (a chemical used as insect repellent) for adults and no more than 10 percent for children when outdoors. Do not use mosquito repellent containing DEET on children under three years of age. Read carefully and follow all directions on the insect repellent package.
  • Hunters should wear gloves when handling and cleaning animals to prevent blood exposure to bare hands. Game meat should be cooked thoroughly.
  • Limit outdoor activities when advised by local officials

a mosquitofish eyes his next meal

Get Mosquitofish

If you have an ornamental pond or pool, mosquitofish may help to control mosquitoes. Mosquitofish, also known as Gambusia, are small predatory fish that eat mosquito larvae. Read the Oregon Department of Fish and Wildlife’s guidance on mosquitofish

Multnomah County residents can get free mosquitofish from May 15-August 30. Please call 503-988-3464 or email to schedule an appointment to pick up mosquitofish at our location in North Portland.


Most of the mosquitoes in our area fall into one of 3 categories:

  • pile of old tires
    Container habitat
    Container breeding mosquitoes. These opportunistic mosquitoes can be found throughout the county in natural and man-made containers of water. Think tree hole in the woods or old tire in the backyard. Culex Pipiens and Ochlerotatus Japonicus are two of the container breeding mosquitoes here in Multnomah County.
  • Floodwater habitat
    Floodwater mosquitoes. These mosquitoes lay their eggs on the ground near bodies of water that flood, usually in the spring time. When the water rises the eggs float on the surface until they hatch into mosquito larvae. Some areas in Multnomah County known to have large populations of floodwater mosquitoes include Government Island, Oaks Bottom Wildlife Refuge and Smith and Bybee Lakes. Aedes Vexans and Ochlerotatus sticticus are two of the floodwater species found in Multnomah County.
  • Summer mosquitoes. Summer mosquitoes will lay eggs on standing water in natural environments or manmade. These mosquitoes include Culex, Culiseta and Anophoeles species.

Need Help Talking to Your Neighbor?

If you feel there's mosquito problem coming from your neighbor's property, you may want to consider first addressing your neighbor or the property owner on a personal, neighbor-to-neighbor basis. A neighborhood mediator from Resolutions Northwest can help you to have productive a conversation and work out peaceful solution.

More Information

Contact Us

Multnomah County Vector Control
5235 N Columbia Blvd
Portland, Oregon