Santa Clara County Vector Control is taking the unusual step of aerial spraying, a clear sign the mosquito population in the marshes is out of control. The target area is a 400-square-mile stretch near Bayshore Road.
The summer salt marsh mosquitoes do not carry West Nile virus but they are aggressive and vicious blood-sucking biters.
People who have been bitten look like they have broken out with mumps or have bad acne, according to Bob Kaufman, field operations supervisor of Santa Clara County Vector Control.
The insects under attack can travel five miles from their breeding grounds, which means people working on their swing at the nearby Palo Alto Golf Course are well within striking distance.
"The golfers playing on the golf course were really getting bitten and they were scattering like crazy," said golfer Tom Sherrod.
The constant nuisance prompted an aerial operation on Thursday that took more than four hours of spraying to cover the marshland.
Vector Control says it can usually control the mosquitoes breeding in the area using ground operations, but an unusual situation this year prompted the air attack.
A critical structure, which in the past has kept high tide from flooding the area, has failed. "We have a broken tide gate structure that's allowing much more water than usual to flood the marshes," said Paul Reyes of Santa Clara County Vector Control.
The stagnant pools of water are ideal for mosquito larvae waiting to hatch. Although the area was closed to the public during the actual spraying, Vector Control says the product being used ? methoprene -- is safe.
"We are using a bacterial derivative that is very specific to mosquitoes and midges so it shouldn't harm any of the other fauna or flora over here in the flood basin," said Noor Tietze, scientific technical services manager for Vector Control.
Unless there is a quick fix for the flood gate, Vector Control says more flyovers may be needed to keep the salt marsh mosquitoes in check.