Rain fuels mosquito invasion in Cook County

Jane Michaels
jmichaels@pioneerlocal.com | @janemichaels22
July 16 6 a.m.

The Four D’s of mosquito defense

Drain: Don’t allow water to stand in cans, containers, pots, discarded tires, or other water-holding containers on your property. Drill holes in the bottom of recycling containers that are left outdoors. Clean clogged roof gutters. Turn over plastic wading pools when not in use. Aerate ornamental pools or stock them with fish. Keep swimming pools clean and chlorinated. Use landscaping to eliminate standing water on your property.

Defend: Wear mosquito repellent. Install or repair screens.

Dress: When outdoors, wear shoes and socks, long pants and a long-sleeved shirt, and apply insect repellent that includes DEET, picaridin or oil of lemon eucalyptus according to label instructions.

Dusk and dawn: Take extra care to use repellent from dusk to dawn when mosquito activity is the highest.

For more information, visit dupagehealth.org/ftb and follow Fight the Bite on Twitter @fight_the_bite or become a fan on facebook.com/fightthebitedupage

Nuisance mosquitoes are definitely living up to their name this year as wave after wave of the blood-thirsty insects swarm and then alight to bite.

“It’s insane,” agreed Paul Geery, biologist and assistant manager of the Desplaines Valley Mosquito District in western Cook County.

“It’s been a long time since we’ve seen this much water lying around everywhere,” Geery said. “This whole region has been inundated with rain.”

Seasonal crews have been kept busy treating larval sources to stem the tide of the invasion, fueled by frequent rainstorms, flooding and standing water. The insect has a three-week life cycle and hatches in 7 to 10 days in warmer weather, or 2 to 2.5 weeks when it’s cooler.

“We’re seeing water in vacant lots and backyards that we’ve almost never seen before,” Geery said. “If things stay really wet, this constant breeding could continue all season.”

Geery said it’s difficult to estimate the number of mosquitoes in this year’s onslaught compared to other years. He is in the process of gathering data and spearheading constant spraying of breeding wetlands to kill larvae.

“We’re definitely going through a lot of pesticide,” he said.

Geery said it’s ineffective to spray adult mosquitoes, a practice discontinued some years ago in the district, which encompasses 31 villages over 77 square miles in Lyons, Oak Park, Proviso, Riverside and River Forest townships.

“I wish we had a tool that could get at a lot of adults, and I wish the others would just honor our borders,” he said. “Even if we could kill all the ones in our area, within two or three days it could be right back up to where it was. They have a 15 to 20 mile radius they can fly.”

But the news is better in tracking a second mosquito strain, the Culex pipiens, which carries the West Nile virus and can prove deadly for a few people with certain health conditions.

The virus is spread by birds and mosquitoes, which feed on infected birds and later, other animals. Also known as house mosquitoes, the insects prefer hot, dry conditions and stale standing water for breeding.

Six pools have tested positive for West Nile virus out of 516 pools throughout the district, each with 50 or more mosquitoes in the sample.

“That’s at a fairly low level,” Geery said. “There’s always a risk in the summertime. You could get really unlucky and be bit by one of the few mosquitoes carrying the virus.”

The mosquito population of both strains depends on the weather and can be very difficult to predict.

“If we get high temperatures and it dries up, then it could get really messy,” Geery said, referring to a jump in the Culex pipiens population.

To avoid being bitten, Geery advises residents to avoid going out at dawn and dusk, wear long sleeves and long pants and use a repellent containing DEET.

“Keep an eye on your yard,” he said. “The season for West Nile isn’t over. Watch for areas holding water, like buckets, bird baths and wading pools, and clogged gutters can be an issue.”