The Facts: Wetland and the West Nile Virus

The two mosquito species known to transmit the West Nile virus in Iowa are not prevalent in natural or restored wetlands, according to Jennifer Anderson-Cruz, a biologist with the USDA-Natural Resources Conservation Service.

Culex pipiens and Culex tarsalis actually prefer briefly inundated water sources such as clogged gutters, unattended bird baths and waste tires. Anderson-Cruz says these species proliferate in polluted waters where natural predators and competitors cannot survive.

“Mosquito numbers are controlled in natural wetlands by the multitude of mosquito predators living there,” she says. “Dragonflies, swallows, frogs and salamanders, which are common inhabitants of natural wetlands, feed on mosquitoes and mosquito larvae.”

In addition, wetlands provide habitat for mosquito competitors, such as tadpoles and algae-eating aquatic insects, which may deter egg-laying by female mosquitoes and compete with mosquito larvae for food.

Anderson-Cruz warns that if wetlands are degraded by pollutants, such as nutrients or organic waste, or if predators and competitors are eliminated by incorrect use of pesticides, then it is possible for mosquitoes to proliferate in a wetland. “It is important to restore and manage for ecological stability in wetlands, controlling mosquitoes with natural checks and balances,” she says.

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