County aims to take bite out of mosquito breeding on Thursday | News | Palo Alto Online |


County aims to take bite out of mosquito breeding on Thursday

Palo Alto Baylands to receive aerial spraying, trails to temporarily close

In order for all area residents to have important local information on the coronavirus health emergency, Palo Alto Online has lifted its pay meter and is providing unlimited access to its website. We need your support to continue our important work. Please join your neighbors and become a subscribing member today.

Palo Alto Baylands trails will be closed for several hours on Thursday for aerial treatment of mosquitoes, the Santa Clara County Vector Control District said in a press release issued Tuesday.

A helicopter crew will fly over the Baylands with a spray that targets the winter salt marsh mosquito (Aedes squamiger) with naturally occurring microbes and a mosquito-specific hormone. The treatment has been safely and effectively used by the county annually since 1992, the district said.

The aerial spraying is scheduled to start at 7:30 a.m. and will last a few hours.

"Current conditions create a high probability that a significant number of salt marsh mosquitoes will become adults in a few days if left untreated. This species is known to bite viciously during the day and can fly more than 15 miles from its breeding grounds to feed on humans and other mammals," the district said.

The crew will cover large areas of the Palo Alto Flood Basin marsh to minimize impact to the marsh habitat. A map of the spray area can be found here and information about mosquito control can be found at

The same area was treated Feb. 12 for the winter salt marsh mosquito. It is roughly bordered by Adobe Creek to the north, Adobe Creek Loop Trail to the east, East Bayshore Road to the south and Mayfield Slough to the west.

"Recent rains have provided the ideal environment for mosquito larvae to develop in hard to reach areas of the marsh. These treatments will help reduce adult mosquito populations in the area," Vector Control District Manager Dr. Nayer Zahiri said.

The area will be treated with a naturally occurring soil bacterium (Bacillus thuringiensis var. israelensis, or Bti), which activates when consumed by mosquito larvae, and a mosquito-specific treatment (methoprene) that prevents them from becoming adults. The ecology-friendly application is short-lived in the environment and is not harmful to birds, fish, other insects, wildlife or humans, the district said. More information about these products is available at the vector control district's website.

The helicopter crew might make low-altitude passes over trails surrounding the treatment area. The district advises the public to avoid areas where the helicopter is operating. Staff will post signage at locations around the treatment area to alert the public.

The winter salt marsh mosquito lays its eggs in the moist soil in late spring and early summer. The eggs can lay dormant for many years, even after repeated flooding. The district asks the public to report mosquito-breeding sources. People can prevent mosquito breeding by dumping standing water on properties, wearing long-sleeved shirts and long pants and applying repellent when outdoors to prevent mosquitoes from biting.

For free assistance on mosquito control, the public can contact the district office at 408-918-4770, or by filling out a service request online.


Follow the Palo Alto Weekly/Palo Alto Online on Twitter @PaloAltoWeekly and Facebook for breaking news, local events, photos, videos and more.

We need your support now more than ever. Can we count on you?


9 people like this
Posted by pearl
a resident of another community
on Mar 25, 2020 at 11:55 am

Question: Per your headline: Does this mean mosquitoes can breed every day except Thursday? How will they know? Are you going to put a sign up? Thank you.

6 people like this
Posted by In Midtown
a resident of Midtown
on Mar 25, 2020 at 12:25 pm

OMG Pearl, you're hilarious! :-D

We have a house next door to us waiting for demolition. It's been empty for a couple of months and the pool has standing water in it. Can they fly by and spray that too please?

6 people like this
Posted by Trump fired the national pandemic team
a resident of Evergreen Park
on Mar 25, 2020 at 12:46 pm

> Can they fly by and spray that too please?

Ask Pearl. Apparently, they have some free time on Thursdays.

4 people like this
Posted by pearl
a resident of another community
on Mar 25, 2020 at 2:12 pm

If the Aedes squamigers (mosquitoes) knew all the publicity their sex life was getting, they'd probably be willing to hold off for some additional days. Just sayin'. :)

Don't miss out on the discussion!
Sign up to be notified of new comments on this topic.


Post a comment

Posting an item on Town Square is simple and requires no registration. Just complete this form and hit "submit" and your topic will appear online. Please be respectful and truthful in your postings so Town Square will continue to be a thoughtful gathering place for sharing community information and opinion. All postings are subject to our TERMS OF USE, and may be deleted if deemed inappropriate by our staff.

We prefer that you use your real name, but you may use any "member" name you wish.

Name: *

Select your neighborhood or school community: * Not sure?

Comment: *

Verification code: *
Enter the verification code exactly as shown, using capital and lowercase letters, in the multi-colored box.

*Required Fields

Get fact-based reporting on the COVID-19 crisis sent to your inbox daily.

Singapore's oldest cafe was about to open in Palo Alto. Then, the coronavirus hit.
By Elena Kadvany | 3 comments | 6,660 views

A Pragmatic Approach to A Trillion Trees
By Sherry Listgarten | 4 comments | 4,270 views

Repairing a Disagreement with your Beloved & “Physical” vs. “Social” Distancing
By Chandrama Anderson | 2 comments | 2,974 views

Coronavirus: my early April thoughts – and fears
By Diana Diamond | 12 comments | 2,705 views

Profiteering off medical equipment and its export unimpeded (COVID-19)
By Douglas Moran | 9 comments | 2,041 views