Floodwater mosquitoes are back 7.23

Posted in 2008 July

By DAVID GREEN

We had such a great summer going. Whatever happened?

Heavy rain + hot weather = mosquitoes.

And we’re not talking about just any old mosquito. The 7.5 inches of rain in the first nine days of July brought a return of the floodwater mosquitoes—a particularly pesky variety that’s just as happy to do its work on a sunny, breezy day as its tamer cousins are at nightfall.

“We have a large population of floodwater mosquitoes on the wing right now,” said Dr. Ned Walker, a Michigan State University professor who studies mosquito biology and control.

Walker explained last September—when the species was vexing residents in this area—that they don’t actually lay their eggs in water. Instead, the female deposits eggs in areas that are likely to be flooded.

Eggs can remain dormant for years until the right combination of water and temperature occurs, then out they come—to feed and lay more eggs during their two-week life span.

If more heavy rains arrive, there could be a lot more of the floodwater mosquito around before cold weather arrives in the fall.

“That seems to be the pattern this summer,” Walker said. “We’re getting fairly regular heavy rainfalls.”

Now, with low ground so saturated, it doesn’t take much to flood, Walker noted, and the mosquito population could continue to increase.

If there’s a good side to the issue, it’s that the floodwater mosquitoes found in this area are just pests rather than disease carriers.

Actually, they can be carriers of West Nile virus, Walker said, they just aren’t good transmitters. Although the virus may be present in a mosquito’s body, it doesn’t readily spit it back out.

There are more important carriers of the virus, but the Ades trivittatus species—probably the small mosquitoes going after the face these days—are strong carriers of the dog heartworm larva.

Control

“It’s really a struggle to do community-based mosquito control,” Walker said. “It takes funding and organization.”

Many communities, such as Morenci and Fayette, have spraying programs in which units are pulled along streets to deliver an insecticide.

That method has limited effectiveness, he said, but it can work quite well if the weather conditions are just right. Very low wind and a thermal inversion in the evening are ideal, Walker said, but Mother Nature generally doesn’t provide the optimum conditions.

A more effective program would require spraying foliage around the borders of yards, but this requires a ground crew and more equipment.

Many communities have even cut back on the spraying routine, he said, due to financial hardship.

With the first frost probably two months away, hope for gentle rains instead of the heavy downpours. Otherwise, the floodwater mosquitoes and their aggressive, dive-bombing ways could be with us off and on for several weeks.

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