Mosquitoes and floods

It is certainly true that the recent floods will increase the population of mosquitoes in the state. However, it doesn’t necessarily mean that the risk of getting West Nile Virus will increase -- at least not right away.

Ralph Williams, a Purdue entomology professor, explains that Culex mosquitoes, which carry the West Nile virus, generally breed in places where standing water remains for a period of time -- such as containers or logs. Flooding actually helps wash away and destroy eggs laid by these disease carriers. But populations of other mosquito species, usually referred to as "nuisance mosquitoes," explode after flooding. Nuisance mosquitoes lay eggs above the waterline that remain dormant for several months. When water levels rise, the eggs hatch, resulting in swarms of new mosquitoes. Generally, these mosquitoes are harmless.

Dr. Williams says the risk of West Nile will increase once things dry out and there are isolated pockets of stagnant water in the usual places again. Flood waters that take days to drain should not be of concern since Culex mosquitoes like to breed in water that collects in one place for a long time. Draining standing water from gutters, flower pots and other containers, ornamental pools and ditches is the best way to keep disease-carrying mosquitoes at bay.

Resources:

Find ways to avoid being bitten by West Nile Virus carrying mosquitoes.

Learn more about how floods can delay the onslaught of disease-carrying mosquitoes.

Peruse some frequently asked questions relating to the use and safety of insect repellent.

August 2, 2003