Benton County residents with bees or fish ponds may want to cover them tonight while a plane flies overhead at 300 feet spraying for adult mosquitoes.
The Benton County Mosquito Control District plans to spray between 8:45 p.m. and 12:30 a.m.
The aerial spraying will focus on certain areas of Richland, Kennewick and West Richland mainly along the Yakima and Columbia Rivers, and in rural locations near Prosser and Mabton.
Mid-July to mid-August is said to be the most active time of year for the mosquitoes that carry West Nile virus.
In 2009, 38 people became sick from West Nile virus after being exposed in Eastern Washington or out of state. One Sunnyside woman died from the virus.
The virus also was detected in Washington in 22 dead birds, one dog, 346 mosquito samples and 73 horses.
Half of the infected horses died or were euthanized. Vaccinations and yearly boosters for horses are effective in preventing serious illness, according to the mosquito control district.
The product to be sprayed tonight includes the active ingredient Permethrin, a synthetic chemical used in insecticides and insect repellent. That chemical is highly toxic to cats and fish.
The product is labeled for use in residential and agricultural areas, the district said. About 0.35 ounces will be applied per acre.
In addition to bees and fish ponds, people are advised to wash any fruits and vegetables that may have been exposed to pesticides before eating them.
"The mosquitoes can grow from egg to adult in just a few days, making it important to empty water around your home frequently," the mosquito control district said in a news release.
People living in areas where West Nile could spread also should use insect repellent while outdoors and make sure their home's screens and windows are free of holes and cracks.
The signs that you've been bitten by a mosquito carrying the virus are flu-like symptoms, though the majority of people won't get sick. Mild symptoms including headache and fever often go away without treatment.
The district said weather conditions could postpone the application.
For more information, go to mosquitocontrol.org.
People who notice dead birds in a neighborhood are urged to call the district immediately because birds can be tested if reported early.
The West Richland-based office can be reached at 509-967-2414.