Mosquitoes are more than a nuisance! They can carry and transmit
diseases that can make people very sick. Even when they don’t
transmit disease, their bites may be uncomfortable or become
Controlling mosquitoes interrupts the disease transmission cycle
and protects people from disease.
How We Control Mosquitoes
The District controls mosquitoes through a program of integrated
mosquito management (IMM). This program focuses on controlling
mosquitoes in their larval stage and preventing problems before
Larval control has many benefits:
Lower toxicity. The pesticides used to
control the larval stage are much less toxic to the environment
and are highly specific to mosquitoes.
Less pesticides. The pesticides are
applied to a smaller area than would be required for treatment
of adult mosquitoes.
Less disease. Targeting immature
mosquitoes kills them before they are capable of transmitting
Sometimes, however, it is also necessary to control adult
mosquitoes, such as when we find that they are carrying a disease
that can be transmitted to humans.
Water that collects underneath buildings, in storm drains, vaults
and other underground sites in San Mateo County are very
significant sources of mosquito development. These sources are
the preferred habitat of the northern house mosquito (Culex
pipiens), which is an efficient vector of West Nile virus. Adults of Culex
pipiens are most abundant during the summer.
The District will deliver fish, at no additional cost, to county residents for control of mosquitoes in backyard ponds. The water in the pond must first be treated to remove chloramine (a sterilizing agent that is present in tap water). Products to remove chloramine can be purchased at a local pet store or aquarium specialist.
San Mateo County Mosquito and Vector Control District takes a
preventative approach to mosquito control. Whenever possible,
mosquitoes are controlled in their immature stages, before they
emerge as biting adults capable of transmitting disease to
Sometimes, however, adult mosquito populations become a threat to
human health. When this happens, information collected through
mosquito surveillance is used to make the decision to reduce
adult mosquito populations.