Clark County Mosquito Control District works to reduce mosquito population


The mosquito population this year is higher than usual in Clark County despite a mild mosquito season in 2021. 

The Clark County Mosquito Control District has been working to reduce the population since April and continually strives to lower the numbers in areas with high concentrations of mosquitos across the county. 

Mosquito species that are active in Clark County lay their eggs in damp soil along rivers during late spring and early summer. Once mountain snow melts and water levels rise, those areas become covered in water and the eggs hatch, the release stated. 

Since the spring and summer seasons were mostly dry in 2021, there were lower water levels and fewer mosquito eggs that hatched as a result. This year, the county faced record rainfall, which caused the Columbia River to reach the flood stage in June, the release stated. As hundreds of acres around local rivers flooded, mosquito eggs hatched, which included the eggs that did not hatch last year. 

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

This spring, the district used a helicopter to treat more than 1,600 acres of mosquito breeding grounds with larvicide. Technicians are also working to set traps to identify areas with large adult mosquito populations and to use trucks to treat those areas. 

According to the release, the district is currently working on more than 300 requests for services over the last three weeks. 

The release also stated mosquito control district technicians are treating thousands of catch basins around the county to prevent mosquitoes from hatching that may carry the West Nile virus. The technicians trap adult mosquitos in those areas to contain the virus. Clark County has never had a positive test result in a mosquito sample, although the virus has been detected in mosquitoes from other parts of the state, stated the release. 

The mosquito species currently active in Clark County don’t carry human diseases, but their bites can cause discomfort. Clark County Public Health urges residents to avoid mosquito bites by following these steps:

  • Install or repair screens on windows or 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 like those with DEET, picaridin, IR3535, or oil of lemon eucalyptus. Use especially at dawn and dusk. Read the label carefully and follow the instructions for applying repellents, especially when applying on children. 

The release stated Clark County residents can also prevent mosquitoes from breeding on their property by following these 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, and clean clogged gutters.
  • Properly maintain swimming pools.
  • Check for containers or trash in hard-to-see places, like under bushes.

The Clark County Mosquito Control District will continue to monitor the county until the end of September, the release stated. 

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