| INTEGRATED
MOSQUITO MANAGEMENT |
Mosquito control in the United States has evolved from
reliance on insecticide application for control of adult
mosquitoes to Integrated Pest Management (IPM). Those
IPM programs that focus on mosquito control are also
known as Integrated Mosquito Management (IMM) programs.
Most IMM programs employ control measures in a hierarchical
manner that emphasizes prevention. Surveillance of mosquito
populations and mosquito-borne diseases is essential
to the program. Control proceeds from the more permanent,
generally more “environmental friendly”
measures of source reduction, and water management,
through biological controls and highly specific larvicides,
to the use of chemical controls such as adulticides,
only after other measures prove to be insufficient or
not feasible. This hierarchy has been endorsed by the
US Environmental Protection Agency (USEPA), the Centers
for Disease Control and Prevention (CDC), the New York
State Department of Health (NYSDOH), and the American
Mosquito Control Association (AMCA). Virtually all IMM
programs include:
• Surveillance
• Source reduction
• Public outreach and education
• Larval control
• Adult control
• For
detailed information see Task 3 - Literature Review
(Book4 and Book
5)
Surveillance of mosquito populations and mosquito-borne
diseases is a critical component of IMM. Mosquito control
districts routinely sample known breeding areas for the
presence of mosquito larvae. Adult traps are deployed
across the County to assess the distribution of particular
mosquito species, population densities, and the presence
of mosquito-borne diseases. Decisions to employ various
control measures are based on factors such as the presence
of disease, the distance from breeding areas to populated
areas, the mosquito species present, their number and
distribution, the weather, and the control agent to be
used.
Source reduction involves the elimination
of mosquito larval habitats or management that renders
the habitats unsuitable for larval development. Public
education plays an important role in source reduction,
as mosquitoes can breed anywhere water collects, even
temporarily. Water management is a form of source reduction
that is practiced in both freshwater and saltwater environments
to reduce the need for pesticide applications. Existing
ditch systems are maintained to drain water from breeding
habitats to interrupt mosquito life cycles and to create
waterbodies that might support populations of fish that
would prey on immature mosquitoes. Impoundments are also
used in parts of the country to maintain water levels
such that the Aedes and Ochlerotatus spp. mosquitoes will
not deposit their eggs on marsh soils. In Suffolk County,
water management accounts for approximately 70 percent
of vector control operations.
| PUBLIC
OUTREACH AND EDUCATION |
Public outreach and education can bring
important information to the community on methods to reduce
residential mosquito breeding areas and products that
can repel mosquitoes and provide protection against their
bites. It also includes responding to complaint reports
and conducting public presentations to civic groups and
other groups. Further information on Suffolk County’s
efforts to control mosquitoes can be found on the County’s
website: www.co.suffolk.ny.us
by navigating to ‘Mosquito Control,’ under
‘Departments.’
Larval control or larviciding is the
process of applying natural or formulated agents to control
mosquito larvae and pupae. Larviciding was originally
implemented as a malaria control measure in the early
1900s and has become an important method of mosquito control.
Larvicide treatments can be applied from the ground, usually
via truck-mounted equipment, or from the air, via fixed-wing
or rotary-wing aircraft. Larval control is often accomplished
through biological control (the use of various organisms
to consume mosquitoes). These can include predators such
as fish, birds, insects, parasites such as nematodes,
and bacteria. The most commonly used biocontrol agents
include the mosquito fish (Gambusia affinis and G. holbrooki),
which prey on mosquito larvae, and the bacteria strains,
Bacillus thuringiensis var. israelensis and Bacillus sphaericus,
which attack the digestive system of mosquito larvae.
Larvicidal agents commonly utilized in IMM programs include:
1. Temephos – An organophosphate
compound, used since the early 1950s, that inhibits
the activity of cholinesterase enzymes at the neuromuscular
junction, causing paralysis and death in insects.
2. Methoprene – An insect growth
regulator (IGR) that mimics a naturally occurring
insect hormone and prevents the adult mosquito from
emerging.
3. Bacillus thuringiensis var. israelensis
(Bti) and Bacillus sphaericus (Bs) –
Naturally occurring bacteria which, when ingested
by mosquito larvae, attack the gut causing death.
4. Surface Control Agents –
Monomolecular films that reduce the strength of the
water surface, making it unable to support larvae
and pupae, causing them to drown. They can also cause
egg-laying females to drown.
Suffolk County Vector Control applies larvicides
as part of their Integrated Pest Management Program.
Treatment of mosquitoes at the larval stage is preferred
since the larvae are concentrated in a centralized
location. Larvicidal agents used by the Department
include Vectobac® (Bti), Vectolex® (Bs), and
Altosid®, (methoprene).
Adult control is the most visible
practice exercised by mosquito control operations. As
with larvicides, adulticides can be applied either by
ground or by air, most commonly via ultra low volume
or thermal fogging techniques. Factors that contribute
to the delivery of an effective adulticide dose include:
target mosquito species, droplet size, dosage rate,
and environmental conditions. Delivery systems are managed
to apply the proper dosage to achieve maximal mosquito
control and minimal unintended impacts. Suffolk County
does not utilize specific numerical triggers to initiate
adulticide applications. Many factors are considered,
including trap counts, landing rates, citizen requests
for service, area history, species causing concern,
mosquito age, and potential for viral transmission.
Adulticide agents commonly utilized in IMM programs
include:
- Organophosphates – These pesticides that contain
phosphorus from one of the phosphoric acids have been
used for mosquito control since the early 1950s. They
inhibit the activity of cholinesterase enzymes at
the neuromuscular junction, causing paralysis and
death. Compounds include malathion, fenthion, naled,
and chlorpyrifos.
- Pyrethrins and Pyrethroids – Natural pyrethrins
(pyrethrum) are extracted from chrysanthemum flowers
and kill adult mosquitoes by affecting their nervous
systems. Pyrethroids are synthetic analogues of the
natural pyrethrins, and include resmethrin, sumithrin,
and permethrin.
- Insect Growth Regulators – These are chemicals
that alter the growth and development of insect larvae
and prevent them from reaching the adult stage. Methoprene
is a commonly used growth regulator.
- Synergists - Not in themselves considered toxic
or insecticidal, synergists enhance the activity of
pesticides by preventing or delaying the ability of
insects to metabolize and expel the chemicals. Piperonyl
butoxide is a commonly used synergist.
If larval efforts fail to prevent a brood of mosquitoes,
the county may elect to use adult control chemicals,
which are applied using ground or aerial applications
of ultra low volume (ULV) aerosols. The adulticides
utilized by the county include Scourge® (Resmethrin),
Anvil® (Sumithrin), and Fyfanon® (malathion).
Resmethrin has been used since 1995 in both truck-mounted
ULV foggers and, when necessary, in aerial applications.
Sumithrin has been used since 1999 in truck-mounted
foggers. Malathion has been in use for nearly twenty
years.
|
Integrated Mosquito Management
