Flooding rains lead to bumper crop of mosquitoes

  • The recent heavy rains has led to a "bumper crop" of mosquitoes this month, officials say.

    The recent heavy rains has led to a "bumper crop" of mosquitoes this month, officials say.

Updated 8/10/2010 7:24 AM

So where's the epicenter of the mosquito plague that's hit the region? Anecdotally, I'd say my back yard but it's likely everyone else who can't put a toe outside without getting bitten would disagree.

I recorded three hits in as many minutes Sunday in broad daylight. Basically, anyone venturing outdoors is fresh meat for the blood-crazed swarms. It makes you appreciate the politically correct vampires of the "Twilight" saga who swear off humans.


In technical language, "it's a bumper crop," DuPage County Health Department spokesman David Hass said of this year's outbreak.

To clarify: What we're seeing is a huge jump in the number of floodwater mosquitoes, not to be confused with Culex mosquitoes associated with transmitting West Nile virus.

Floodwater mosquitoes thrive on rain, and nature has obliged this summer, with a deluge of storms - almost twice the normal amount.

Culex mosquito activity is relatively low compared to the extremes of 2002, with no human cases of West Nile virus reported so far. That doesn't mean the threat isn't out there, however.

Here are some questions and answers on the mosquito plague of 2010.

Q. What's with all the mosquitoes this year?

A. Floodwater mosquitoes lay their eggs in low-lying areas and, as water collects, the insects hatch. The more rain the better for reproduction. Culex mosquitoes require stagnant water for breeding so constant rain disrupts hatching. That's why experts say less precipitation will increase Culex mosquitoes.

Q. How many more mosquitoes are out there?

A. In some traps, there has been a 45 percent increase, said Laura McGowan of Roselle-based Clarke, which contracts with myriad suburbs to control mosquitoes. Northwest Mosquito Abatement District Director Mike Czyska reported 13 times the usual amount of mosquitoes found in traps.

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Q. Where is West Nile cropping up?

A. Mosquitoes, birds and other animals testing positive for West Nile have been reported in 18 Illinois counties including Cook, DuPage, Kane and Will. Changing weather conditions could increase those numbers, officials say.

Q. What's the forecast?

A. National Weather Service meteorologist Paul Merzlock reports that the scorching temperatures should abate by mid-August leaving us with highs in the 80s and lows in the 60s. It's the type of weather pattern that isn't conducive to the extreme storms the region's witnessed this summer. And if the rain subsides, that could trigger more Culex mosquitoes.

Regarding rainfall, nearly 16 inches of rain has fallen at O'Hare International Airport since June 1. The norm is 8.3 inches.

Q. Is there relief in sight?

A. "We're already seeing a slight drop in the numbers (of floodwater mosquitoes), but I can't guarantee it's over," Czyska said.

Q. How does this year compare to others for West Nile?


A. There are no human cases in Illinois yet. In 2009, five people were infected - with the first case reported Aug. 31. In 2008, there were 20 cases. Worse years have included 2002 with 884 people contracting the virus, 2005 with 252 cases and 2006 with 215 incidents.

Q. Can you tell what type of mosquito is biting you?

A. It's unlikely. But University of Illinois Extension entomologist Philip Nixon characterizes Culex mosquitoes as "sneaky, quiet biters." Floodwater mosquitoes are noisier. "If it's buzzing around your ears, it's probably not a Culex," he said.

Q. How do I avoid getting bitten?

A. Avoid the outdoors from sunset to sunrise when mosquitoes are on the prowl. Wear bug spray with DEET, picaridin, oil of lemon eucalyptus or IR 3535. Also, eliminate standing water in birdbaths, wheelbarrows and other containers.

Q. Has the economy affected mosquito-control efforts?

A. Clarke reported no significant decline in business, noting that many municipalities have multiyear contracts. The Northwest Mosquito Abatement District, which does its own mitigation, said it has increased spraying of adult mosquitoes because of the influx.

Sources: National Weather Service, Illinois Department of Public Health, Clarke, DuPage County Department of Health, Northwest Mosquito Abatement District, University of Illinois Extension.