Countywide : Vector Control Puts the Bite on Mosquitoes

Mosquitoes are not so different from people. They start their days with a splash of water, enjoy peace and quiet at home, and prefer not to venture out until the weather is warm.

Those similarities make the work of Orange County Vector Control District employees a little easier as they set out to stop mosquitoes where they hatch. They know where to find their target: in the still waters near the beach. In the coastal wetlands of Edison Marsh, Bolsa Chica Marsh, Kadane Oil Lease and the 39 Marsh (named for the highway number of nearby Beach Boulevard), mosquito larvae are making a cozy home and waiting for warm weather, preferably 70 to 80 degrees, before they emerge.

The crew from the pest control department is now testing each area to see how large its population is likely to be.

In standing water where they find a substantial number of larvae, the workers spray what they say is an environmentally safe insecticide, Bti, using fumigation machines strapped to their backs and, occasionally, a helicopter.

The insecticide, scientifically known as Bacillus thuringiensis israelensis, is a bacteria that kills only mosquitoes and aquatic flies.

“We are sensitive to the nature of the environment,” Larry Shaw, a vector control specialist, said Tuesday as he pointed out some of the endangered species of birds that live in the marshes.

The district also uses mosquito-eating fish and a type of petroleum known as Golden Bear, which evaporates over time, to get rid of the pests.

The late-winter campaign will focus on the salt marsh mosquito, known to be a vexing “day biter,” and another winter mosquito known to carry viruses, said Jim Francisco, the district’s education coordinator.

Beginning in April or May and continuing through October, vector control will target flood-control channels and canyons for summer species of the insects.

Because of the recent heavy rains, Francisco said, the district is asking residents to keep an eye on their backyards. Standing water in empty fishponds, swimming pools and old tires provides an inviting breeding ground for mosquitoes, he said.