County works to reduce ‘bigger than usual’ mosquito population

Mosquito season is in full swing. And after a mild season in 2021, this year’s mosquito population is bigger than usual. 

Clark County Mosquito Control District has been working to reduce the mosquito population since April and continues to treat areas with high numbers of mosquitoes across the county. 

As crews work to control the mosquito population, Public Health is encouraging everyone to take steps to avoid mosquito bites and eliminate mosquito habitats on their property.

The species of mosquitoes that are currently active in Clark County lay their eggs in the damp soil along rivers during late spring and early summer. As mountain snow melts and water levels rise, those areas become covered with water and the eggs hatch.

The dry spring and summer in 2021 meant lower water levels, fewer mosquito eggs hatching and a smaller population of adult mosquitoes. This year, however, the region experienced record rainfall, and in June the Columbia River reached the flood stage. As hundreds of acres around local rivers flooded, mosquito eggs began hatching, including any eggs that did not hatch last year.

“All of those conditions culminating at the same time created this year’s perfect storm,” said Mario Boisvert, Clark County Mosquito Control District manager.

This spring, the Mosquito Control District used a helicopter to treat more than 1,600 acres of mosquito breeding grounds with larvicide. Now, technicians are setting traps to identity areas with large populations of adult mosquitoes and using trucks to treat those areas. The District is working to address more than 300 requests for service submitted over the last three weeks. 

Additionally, District technicians are treating thousands of catch basins across the county to prevent the hatching of a species of mosquitoes that can carry West Nile virus. Technicians also trap adult mosquitoes in these areas to test for West Nile virus. Clark County has never had a positive test result in a mosquito sample, though the virus has been detected in mosquitoes in other parts of the state.

The species of mosquitoes currently active in Clark County do not carry human diseases, but their bites can cause discomfort. Public Health is urging residents to take the following steps to avoid mosquito bites:

  • Install or repair screens on windows and doors.
  • When possible, stay indoors during dawn and dusk when mosquitoes are most active. 
  • When practical, wear long-sleeved shirts, long pants, shoes, socks, and hats outside, especially in wooded or wetland areas. 
  • Place mosquito netting over infant carriers when outdoors.
  • Use EPA-registered insect repellents, including those with DEET, picaridin, IR3535 or oil of lemon eucalyptus. Use especially at dawn and dusk. Read the label and carefully follow the instructions for applying repellents, especially when applying on children.

Clark County residents can also do their part to help prevent mosquitoes from breeding on their property by taking these simple steps:

  • Drain standing water from old tires, flowerpots, buckets, plastic tarps and wheelbarrows. 
  • Change water in bird baths, ponds, wading pools, pet bowls and animal troughs at least twice a week.
  • Repair leaking faucets and sprinklers; clean clogged gutters.
  • Properly maintain swimming pools. 
  • Check for containers or trash in hard-to-see places, such as under bushes.

The Clark County Mosquito Control District will continue surveillance and treatment activities throughout the active mosquito season, which usually runs through the end of September. To learn more about treatment activities or to submit a request for service, visit the Mosquito Control District website.