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Rain may cause mosquito increase
Mosquito larvae spend their lives underwater. Containers holding standing water, such as flower pots and old tires, particularly are attractive to mosquitoes, according to Dr. Joe Keiper. (CDC photo)
Monday, July 22, 2013
By BEN R. WILLIAMS - Bulletin Staff Writer
Heavy rainfall is likely to boost the local mosquito population, but there’s still time to take preventive action, according to Virginia Museum of Natural History (VMNH) executive director Dr. Joe Keiper.
With adult mosquitoes, Keiper said, “after the female blood feeds, she produces a batch of eggs and lays those eggs in standing water.”
In large bodies of water, he said, this usually doesn’t present much of a problem, because fish and other animals in the water will feed on the swimming mosquito larvae, which helps to keep the mosquito population in check.
“The real concern that we should have is container breeding,” Keiper said.
Mosquitoes will also lay their eggs in containers that hold standing water; for example, clogged gutters, flower pot trays, kiddie pools and old tires.
Any container that will hold standing water for roughly a week, particularly in hot weather when insect life cycles are accelerated, is capable of producing mosquitoes, sometimes multiple life cycles if conditions are right, Keiper said.
Because of the heavy rainfall our area has received, he added, these containers are being continually replenished, which makes it easy for mosquitoes to breed generation after generation in the same spots.
“The problem is,” Keiper said, “these containers are right next to your house. What you want to do, as a conscientious homeowner, is either remove these containers or drain them.”
By drilling holes in containers that hold standing water, Keiper said, “you reduce greatly the number of mosquitoes around the area where you work or play.”
For situations where draining isn’t an easy option — an ornamental pond, for example — there is another solution, Keiper said.
There’s a type of bacteria, he said, called bacillus thuringiensis, which is commonly used to control different kinds of insects that spend their juvenile lives in water.
“It’s a bacteria that releases an enzyme that gets into the gut of certain kinds of insects,” Keiper said. “This enzyme actually breaks down the gut of the mosquito, and it dies of starvation before it can mature” into the blood-sucking adult form.
This bacteria is made into doughnut-shaped discs, commonly sold under the name “Mosquito Dunks,” that can be purchased at most hardware stores. The discs can be dropped into bodies of standing water, and they release their bacteria for roughly a month, keeping the mosquito population under control during that time, he said.
Because the bacteria are naturally occurring, Keiper said, the discs “are even environmentally safe.”