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Helicopter Treatment for Winter Salt Marsh Mosquitoes Tomorrow

SANTA CLARA COUNTY, CALIF. – Weather permitting, the Santa Clara County Vector Control District (SCCVCD) will apply a biological control agent and insect growth regulator by helicopter on Thursday, February 14, 2013 to reduce the emergence of adult mosquitoes. The treatment is scheduled to start at approximately 8:00 a.m. and last for up to four hours.  The areas to be treated are the Alviso Marsh, Smith Yard Marsh, New Chicago Marsh, and Zanker Marsh.  The aerial treatment is intended to minimize the number of mosquitoes and reduce the risk of mosquito bites to residents in the surrounding communities.
Commonly called the “winter salt marsh mosquito,” Aedes squamiger lays its eggs in the moist soil in late spring and early summer.  These eggs can lay dormant for many years, even after repeated flooding.  High tides and seasonal rains, together with the short days and cooler temperatures of winter, cause the eggs to hatch as early as November.  Although this species has not yet been shown to transmit West Nile Virus, it is known to bite viciously during the day and can fly over 20 miles from its breeding grounds to feed on humans and other mammals. 
SCCVCD has been closely monitoring the development of mosquito larvae in the areas to be treated.  Current field conditions and mosquito growth trends indicate a high probability that a significant number of salt marsh mosquitoes will become adults in early to mid-March if left untreated.  The mosquito fly-off may affect residents from the north coastal areas of the county to as far south as the southernmost part of the City of San José and east to Milpitas.
“Except for last season's unusually dry winter, we've been doing the treatments every year since the District was formed in 1988,” said Acting District Manager Russ Parman, “The aerial operations usually result in a 90 percent reduction in mosquito numbers, and dramatically reduce the extreme nuisance caused by these mosquitoes well into the summer.”
Approximately 728 acres will be treated with water-based formulations of environmentally safe products: methoprene, an insect growth regulator, and Bacillus thuringiensis var. israelensis (Bti).  Bti is a natural bacteria that, when consumed by mosquito larvae, produces an insecticidal protein that kills the larvae.  These products are mosquito-specific and short-lived in the environment. They effectively control the immature (aquatic stage) mosquitoes, but are not harmful to birds, fish, other insects, wildlife, or humans. More information about these products is available at
Access to the areas will be restricted during the four-hour aerial applications, but open to the public immediately afterward. 
The SCCVCD continues to encourage residents to report mosquito-breeding sources and take preventive measures, such as wearing long-sleeved shirts and long pants, and applying repellent when outdoors where mosquitoes are biting.  For more information about mosquito prevention, go to or call 408.918.4770.



Media Contact: Noor Tietze 408-210-5773; Russ Parman 408-593-6176; Victor Romano      408-593-6193
Released: February 13, 2013