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Second Helicopter Treatment for Summer Salt Marsh Mosquitoes Scheduled in Palo Alto Baylands

SANTA CLARA COUNTY, CALIF. --Beginning at approximately 9:00 a.m. on Friday, August 31, 2012 (weather permitting), the Santa Clara County Vector Control District (SCCVCD) will be applying mosquito control products by helicopter to reduce the emergence of adult mosquitoes from the Palo Alto Baylands.
The aerial treatment is intended to minimize the number of mosquitoes and reduce the risk of mosquito bites to residents in the surrounding communities. Aerial treatment is necessary because the areas are extensive and difficult to treat from the ground. The application poses minimal risk of human exposure or adverse health effects and there are no residences or businesses within the area to be treated.
Commonly called the “summer salt marsh mosquito”, Aedes dorsalis lays its eggs in the moist soil just above the water line. 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 when they are submerged in water. 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 up to five miles from its breeding grounds to feed on humans and other mammals.
This is the second aerial treatment of the season, the first being successfully completed last Thursday. A breached tide wall in the Palo Alto baylands has created ideal conditions for the breeding of the mosquitoes by allowing water levels in the basin to rise and fall. SCCVCD has been closely monitoring the development of mosquito larvae, and current field conditions are producing continued egg-hatch. Recent adult “fly-offs” have created considerable discomfort for residents and businesses in nearby areas.
Approximately 360 acres will be treated with 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, activates 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, most other insects, wildlife, or humans. Unlike the recent Ultra-Low Volume aerosol treatment operations targeting adult mosquitos, these products will be applied mixed in ten gallons of water per acre to maximize delivery of the control products into the marsh habitat. More information about these products is available at
Access to the baylands will be restricted during aerial applications, but open to the public immediately afterward.
VCD 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, Jose Colome (408)593-6176, Bob Kaufman (408)593-6170, Santa Clara County Vector Control District
Posted: August 30, 2012