Possible mosquito swarms incoming

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Jake Magee
Friday, June 20, 2014

JANESVILLE—Mosquitoes suck in more ways than one. But the storms that hit Rock County this week might cause an infestation of Wisconsin's most annoying pest.

“There is a relationship between rainfall and mosquito activity,” said Patrick Liesch, assistant researcher for the UW-Madison Insect Diagnostic Lab. “Mosquitoes are associated with water, so whenever we get more rainfall, that's an opportunity for mosquitoes to lay eggs.”

In warm weather, it takes about seven to 10 days for mosquito eggs to hatch. They can take weeks in cooler weather.

“It wouldn't surprise me if in a week and a half to two weeks we start seeing a lot of mosquitoes,” he said.

Still, it's possible the storms have washed mosquito eggs away. If mosquitoes lay eggs in a pool of water in a forest and a heavy rain comes in, it might be strong enough to flush the eggs onto solid ground, killing the larvae, he said.

Liesch is unsure when mosquito season will peak.

“It's really hard to tell because it can be very dependent on the weather,” he said. If July and August are as dry this summer as they were last year, many mosquitoes will die out.

It's also difficult to predict the risk of mosquito-carried diseases because of the variety of species. Wisconsin alone has 50 different species of mosquitoes, Liesch said.

Normal bug zappers use ultraviolet light to attract insects and electrocute them, but they don't work well on mosquitoes. The carbon dioxide humans emit attracts female mosquitoes, which bite for the protein in human blood to help develop their eggs.

Carbon dioxide traps can cost hundreds of dollars and need to be maintained and fueled by propane, making them impractical for some people.

Foggers are largely useless as well, Liesch said. They repel insects when sprayed in a yard but must be used periodically to have any lasting effect.

Furthermore, they kill other insects besides mosquitoes and might even harm small rodents, he said.

“If you want to protect yourself, the best thing to do is use repellents. If you're out in the evening having a barbecue, wear a long-sleeved shirt and long-sleeved pants,” Liesch said. Not going outside at dusk and dawn when mosquitoes are most active helps, too.

A steady breeze of eight to 10 mph lowers the chance of mosquito bites because wind makes it hard for insects to fly.

Concerning repellent brands, Liesch said products that use DEET are a “gold standard” but that other products are effective, too.

It's important to follow repellents' directions to minimize risk and maximize effectiveness, he said. Also, some products might be safe to apply to skin while others can only be used on clothing.

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