Vector Control urges residents to empty standing water to stop mosquito spread

May 10, 2012

Jim Stafford wades into the swampy wetlands located throughout Multnomah County on a May morning looking for mosquito larvae.

As a Multnomah County Vector Specialist, Stafford is looking for signs of the biting insects that can carry diseases such as West Nile virus. The county’s surveillance and control teams focus their efforts on controlling immature mosquitoes in the floodplains of the Columbia and Willamette Rivers, swamps, storm water facilities and other water-holding sites. They work closely with property owners and state and local fish and wildlife managers to identify problems and protect humans and wildlife.

But to keep biting mosquitoes out of neighborhoods, Jim Stafford needs your help.

Mosquitoes need water to breed. County staff are urging residents to please survey their outdoor decks, yards and work sites and remove or cover any containers which hold standing water.

An invasive mosquito, Ochlerotatus japonicus, the Asian Rock Pool mosquito, has spread into new areas in Multnomah County since it was originally detected in 2006. This species is originally from Japan, Korea, Taiwan and South China and has slowly spread into the United States through global trading and the transport of tires.

The species is an aggressive day and night time biter. It prefers containers common to homes and gardens such as wheelbarrows, wading pools, buckets, tires, uncovered boats and rain gutters.

“Ironically, this species develops in early spring; a time when most people do not think mosquitoes are active,’’ says Chris Wirth, manager of vector-borne disease surveillance and control and code enforcement. He says if everyone does their part, our community can reduce mosquito breeding sites before summer arrives.


To protect yourself:

  • Remove mosquito-breeding grounds by emptying standing water in flower pots, buckets, barrels and play equipment.
  • Change the water in pet dishes and bird baths weekly.
  • Empty children’s wading pools and store on their sides
  • Maintain good screens on windows and doors.
  • Many mosquitoes are most active at dawn and at dusk. Consider staying indoors or wear long sleeves and pants that protect skin.
  • Apply repellent with an EPA-registered active ingredient as directed to exposed skin and clothing.

Get more information by visiting the Health Department's mosquito page, or by calling Multnomah County Vector Control at 503-988-3464.