The Santa Clara County Vector Control District plans to treat the Palo Alto Flood Basin for mosquitoes on Wednesday.
The treatment will occur around 7:30 a.m. and will last a few hours, according to the county.
"Current environmental conditions create a high probability that a significant number of mosquitoes will become adults in a few days if left untreated," said Vector Control District Manager Dr. Nayer Zahiri. "This treatment will significantly help reduce the mosquito population and eliminate a fly off of adult mosquitoes."
Using a helicopter, Vector Control District staff will fly over the marshes to spray a "naturally occurring soil bacterium" that will be consumed by mosquito larvae and effectively stunt their growth, the county said in a news release.
The public is advised to avoid the area since the helicopter will reach low altitudes as it treats the area.
The Vector Control District, which monitors vector-borne diseases from insects and other wildlife, regularly surveils the marshes for winter salt marsh mosquitoes. The species is known to be effective carriers of the Western equine encephalitis, which can be transmitted to humans through a mosquito bite.
The agency has used this treatment method every year since 1992, the county said.
For more information on mosquito prevention, visit vector.sccgov.org.