Riechel Reports - Events - City of San Bruno CA
San Mateo Mosquito District September 2021 Department Reports

Article Source:  San Mateo County Mosquito & Vector Control District - CA

Field Operations in August 2021

Searching for Mosquitoes

This summer mosquito service requests are down compared to last year. From May to September last year district staff responded to 312 mosquito calls, and for the same time period this year our technicians have gone to 197 service request for mosquitoes. There are a lot of factors that go into this decline:

     Our technicians are proactively managing their assigned zones and making sure the known breeding sites are controlled in a timely manner

     The Vector control technicians and lab staff do a great job using adult surveillance to identify emerging problems areas for mosquitoes.

     The public has become more aware through our public outreach program about the mosquito life cycle and the importance of dumping and draining containers that are potential mosquito breeding habitats

When our staff do get a call from the public about mosquitoes they respond immediately to identify the species of the mosquito and where they are coming from. Sometimes the assigned technician finds the problem quickly, but if the responding technician cannot find the breeding source within a few days we canvas the neighborhood with 3-4 staff members searching every property for a possible source.

August 2021 Service Requests

Type of Request





Yellowjackets and










Mosquito fish



Insect identification



Dead birds













The total number of service requests is below average for this month of the year (480 compared to an average of 608). This is the lowest number of service requests in the month of August in the past five years. The number of yellowjacket and other wasp requests, while below average for the month of August, remains high. Yellowjacket and wasp requests are common in the summer and will likely remain numerous until the weather cools in autumn. The number of mosquito service requests is also lower than average, because of few Culex pipiens problems this year. Dead bird requests are lower than average as well, because of little West Nile virus activity this year throughout the coastal region. The category of “other” included a variety of request types, such as flies, cockroaches and fleas.

Techs in Action- August 2021

Technician Kim Keyser recently found a concrete drainage ditch that is normally dry in the summer holding water and breeding mosquitoes. Kim treated the ditch and contacted the property management company to adjust their sprinkler system which was the cause of the stagnant water.

Technician Devon MacDonald found a new breeding habitat that was producing many adult mosquitoes. Devon treated the location for adult mosquitoes and contacted the property owners about a potential broken pipe underneath the building.


Lab Activities in August 2021

Yellowjacket Trapping

Yellowjacket wasps are an extremely abundant pest in San Mateo County and the removal of their nests is the District’s most frequently requested service during the summer. These wasps form large colonies underground or in crevices of structures and can aggressively sting and bite. They are predators of other insects but also eat fruit, flower nectar and tree sap.

While yellowjackets are attracted to the food people eat and can become a great nuisance to outdoor diners or picnickers, the biggest threat from them occurs when people accidentally disturb their nest. Yellowjackets will

Yellowjackets guarding the entrance to their nest. Ground nests are hidden and usually detectableonly by small holes in the dirt with yellowjackets entering and exiting.


While the District can assist many residents with yellowjacket nest removal, there are some locations where this is not possible. For example, picnic areas within large parks or yards adjacent to open space are within the flight range of an area too expansive to locate and remove all nests. In these circumstances, residents can use yellowjacket traps and baits to mitigate the problem so they can still enjoy the outdoors during the summer season.

The District is working on a project to determine whether commercially-available lures and baits are effective on yellowjackets in San Mateo County. This year, District staff are evaluating different types of non-toxic traps to discover if one type catches significantly more yellowjackets or other stinging wasps than another. The best trap can then be used as a monitor to assess changes in yellowjacket populations when other tools, such as toxic bait or nest removal, are being used. The District can also use this knowledge to advise residents or recreational organizations on yellowjacket management and control.


Tick Surveillance for Water Year 2020-2021

The San Mateo County Mosquito and Vector Control District conducts annual tick collection and molecular testing via real-time PCR analysis for the pathogens that cause Lyme disease, hard-tick relapsing fever, and human granulocytic anaplasmosis (HGA). All three diseases may be vectored by both nymphal and adult black-legged ticks (Ixodes pacificus). In the 2020-2021 water year, a total of 4,728 adult and 220 nymphal Ixodes pacificus ticks were collected from nineteen parks and open space areas.

Ixodes pacificus ticks collected in San Mateo County (September 2020—August 2021)

Park or Area Name

Adult Ticks


Aņo Nuevo State Park



Costanoa Recreational Area



Crystal Springs and Hallmark Park                 2


Crystal Springs Regional Trail



Eaton Park



Edgewood Park                                            254


Filoli Gardens



Hidden Canyon Park                                      4


North Hillsborough



South Hillsborough                                       319


Huddart Park                                               297


Junipero Serra Park



Laurelwood Park                                                                   272


Montara Mountain Trail



San Pedro Valley Park                                                                   291


Skyline OSP



Thornewood OSP



Windy Hill OSP







Minimum Infection Prevalence of Pathogens in Ixodes pacificus ticks

County wide, adult ticks had a minimum infection prevalence (MIP) of 1.1% of Borrelia burgdorferi sensu lato, 0.70% for B. miyamotoi, and 0.2% for Anaplasma phagocytophilum. Nymphs had an MIP of 2.7% of B. burgdorferi s. l., 1.8% for B. miyamotoi, and 0.9% for A. phagocytophilum. These findings do not differ significantly from prior years.

 Laboratory Report


The MIPs of the three tick-borne disease pathogens in ticks from each site are presented in the next chart. Sites with fewer than 150 ticks collected are omitted because their MIPs are unlikely to reflect the true prevalence of these diseases. Complete pathogen testing results for adult and nymphal ticks, including Dermacentor tick species, will be available on the District website when all testing for the season is complete.

 West Nile Virus Update

The District collects and tests dead birds reported by residents. Dead birds should be in good condition without signs of decay or trauma. All bird species are accepted except water fowl, poultry or pigeons.

To report a dead bird, residents should call the California state West Nile virus hotline at 1-877-WNV-BIRD (1-877- 968-2473). Online reports can be made at westnile.ca.gov.

San Mateo County

As of September 1, 2021, there have been 227 dead birds reported in San Mateo County. Of those, 60 have been suitable for testing and all have tested negative for West Nile virus (WNV). No mosquito pools or sentinel chickens have tested positive for West Nile virus in San Mateo County in 2021.


Statewide, 3,990 dead birds have been reported and 1,241 have been tested with 155 positive results (12%). This is similar to bird data from last year, when 143 dead birds had tested positive at this date. This is low compared to a five-year average of 407 positive dead birds by the end of August. So far in 2021, 1,482 mosquito samples have tested positive for West Nile virus from 24 counties. Statewide, 43 sentinel chickens have tested positive from nine counties and five horses have tested positive from four counties.

There have been 26 human cases of West Nile virus with two fatalities, one from Butte County and one from San Luis Obispo County. Most West Nile virus activity this year within California is in the central valley and southern California, whereas very little activity has been detected within the San Francisco Bay coastal region.


CO2 Traps – Average adult mosquitoes collected per trap per night

The following table and graph show the average number of mosquitoes collected per CO2 trap per night during the month of August compared to the five-year average for the six most common mosquito species in San Mateo County. Culex erythrothorax, a mosquito that breeds in lakes and ponds with tules, was the most frequently collected mosquito in August. The high number of tule mosquitoes this month reflects a large seasonal emergence of this species in Pacifica. Adults of this species are usually present from around April through October. Seasonal helicopter treatments for this mosquito began in July but have not yet successfully suppressed the mosquito population. Additional helicopter treatments will occur in September and October. Numbers of Culex pipiens, the northern house mosquito and typically the most abundant mosquito across San Mateo County, remain below average for this time of year.

Species                                                                        August 2021

5-year August average

Culex erythrothorax



Culex pipiens



Culiseta incidens



Culex tarsalis



Aedes washinoi



Aedes sierrensis




Average number of adult mosquitoes collected in CO2 traps per trap per night during 2021, by month. The graph shows the six most common species of mosquitoes that are collected in traps in San Mateo County.


Average number of adult mosquitoes collected in CO2 traps per trap in one night (average over prior five years). 

Mosquito Larval Samples

The dry summer weather limits the number of mosquito larval samples that are collected. Summer samples are often collected from residential areas that contain water year-round, such as backyard fountains and fish ponds, water under buildings, storm drains, and other containers in yards. Some are also collected from pockets of still water along creeks. This August there were 50 larval samples submitted to the laboratory. The most frequently occurring species in larval samples was Culiseta incidens, the cool weather mosquito, present in 23 of the 50 larval samples. This mosquito is found year-round in a variety of sources, especially backyard fountains and fish ponds. It is not known to transmit diseases. Culex pipiens, the northern house mosquito, was also collected frequently this past month, present in 20 of the 50 samples. This is the most common mosquito causing biting issues in San Mateo County, is a vector of West Nile virus, and is found year-round. District seasonal staff are currently hard at work, treating catch basins across the county in order to control mosquito populations.



Public Health Education and Outreach, Jul-Aug 2021

Website metrics, Newsletters, and Service Request survey responses


In July 2021, there were 3,252 visits to the District website(‘sessions’), an decrease of 24% compared to June 2021.

In August 2021, there were 2,458 visits to the District webpage (‘sessions), a decrease of 24% compared to July 2021.

Decreases are likely due to many links slightly changing in the new website. Traffic will balance with time.

Top 10 pages in July and August 2021:



7.   Rodents


Service request pages

8.   Yellowjacket prevention and control


Biting mites

9.   Yellowjacket nest treatment


Contact us

10. Yellowjacket and wasps – what you


Yellowjackets and wasps

can do






July 2021 newsletter email campaign had 1,665 recipients, 42% opened, 6% clicked a link.

August 2021 newsletter email campaign had 1,676 recipients, 37% opened, 4% clicked a link.

Outreach and Activities

   District staff hosted tables at the San Mateo County Parks’ ‘Movie in the Park’ night at Coyote Point on July 31. Tables included a mosquito aquarium display, pill and sow bugs (to relate to a character in the movie being screened), insect repellent education and handouts, and other small items for children and families.

   Staff attended storytimes hosted by Redwood City Public Libraries in Jardin del Ninos and Stafford Park in late July and early August. Children enjoyed a mosquito-themed story, adults learned about District services, and families were able to view resin-encased insects and take home an insect-themed book for their home library.

   Staff attended the end of summer program event organized by the Police Activities League in the North Fair Oaks neighborhood of Redwood City. Tables included a mosquito aquarium display,

insect repellent information and handouts, information for adults about District services, and insect-themed books for children to take home.

  Continued review, reorganization, and development of the new website was a priority, with particular attention to slimming the website, standardizing pages, and increasing accessbility.

Resident Comments

  “The technician that came was marvelous!"

  “The agent who came to my house was knowledgable, thorough, helpful and polite.”

  “Very impressed and appreciative of the timely service. Thank you.”


Information Technology Activities in July-August 2021

Cybersecurity Training and Network Establishment at 1415 N. Carolan


Staff and Board Cybersecurity Training Internet Installation

Cybersecurity Training

The District implemented a cyber security training process in July. The first topic covered was social engineering. Social engineering is a technique used by people with malicious intent to manipulate a target to give up confidential information. Social engineering attempts to establish trust with the target and then trick the target into sharing critical information. The best defense against attacks using social engineering is training users to understand the concept of social engineering and how to identify emails or others interactions that may be social engineering. In July, District staff and trustees were sent a short training covering social engineering. 89% of staff and 72% of trustees completed the training.

As phishing attempts have increased in frequency and sophistication, the District must rely on staff and trustees to stay vigilant. Phishing and malware training was recently sent out for completion by District staff and trustees. Results will be presented at a future Board meeting.

Internet Installation

District staff worked to install internet capabilities at the 1415 N Carolan Ave property. Staff will continue to proactivitely prepare and support network needs during the District’s development of the property to suit District needs.


Staffing update

The Operations Director job posting is now closed. Staff received three applications meeting the announcement criteria. Interviews for the position are tentatively scheduled for the second week in September. As a reminder, this is a newly created position that will replace the position of Assistant Manager. The position, approved at the June Board meeting, will serve as an administrative extension of the Manager and have both management and supervisory responsibilities. The primary role will be to direct operational programs and its staff however they may act on behalf of the Manager in the Manager’s absence.


The District is the recipient of the Transparency Certificate of Excellence and District of Distinction Accreditation and the Special District Leadership Foundation (SDLF) for the third time. The District is one of only three mosquito and vector control districts in California to earn both awards.

As a reminder, the Special District Leadership Academy will be held on September 26-29, 2021 in Lake Tahoe.

Oxitec in the news

Lab Director Nakano provided an update on the Sterile Insect Technique or SIT. On the heels of the presentation, you may have heard even more news about SIT. This is exciting technology may quickly become a reality in California because of Oxitec. The reason they are in the media is following the successful launch of its FriendlyTM Aedes aegypti pilot program in Florida, Oxitec has requested approval from the U.S. Environmental Protection Agency (EPA) to pilot its technology in California in partnership with local

government agencies such as mosquito districts.

As part of the application process, the public will have an opportunity to submit a comment in the Federal Register. Then, the EPA will review and respond to the comments before issuing a decision. If the EPA approves Oxitec’s California amendment, more approvals would be necessary on the local level. This method of control is only being considered for invasive mosquitoes.


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