United States
Environmental
Protection Agency
Prevention, Pesticides
and Toxic substances
(7506C)
May 2000
735-F-00-002
FOR YOUR INFORMATION
Larvicides for Mosquito Control
EPA evaluates and
licenses pesticides
mosquito officials
select control
measures that best
suit local conditions
he Environmental Protection Agency (EPA) evaluates and registers
(licenses) pesticides to ensure they can be used safely. These pesticides
include products used in the mosquito control programs which states and
communities have established. To evaluate any pesticide, EPA assesses a
wide variety of tests to determine whether a pesticide has the potential to cause
adverse effects on humans, wildlife, fish and plants, including endangered species
and non-target organisms.
Officials responsible for mosquito control programs make decisions to use
pesticides based on an evaluation of the risks to the general public from diseases
transmitted by mosquitoes or on an evaluation of the nuisance level that
communities can tolerate from a mosquito infestation. Based on surveillance and
monitoring, mosquito control officials select specific pesticides and other control
measures that best suit local conditions in order to achieve effective control of
mosquitoes with the least impact on human health and the environment. It is
especially important to conduct effective mosquito prevention programs by
eliminating breeding habitats or applying pesticides to control the early life stages
of the mosquito. Prevention programs, such as elimination of any standing water
that could serve as a breeding site, help reduce the adult mosquito population and
the need to apply other pesticides for adult mosquito control. Since no pesticide
can be considered 100% safe, pesticide applicators and the general public should
always exercise care and follow specified safety precautions during use to reduce
risks. This fact sheet provides basic information on larvicides, a type of pesticide
used in mosquito control programs.
What are Larvicides?
larvicides kill insect
larvae
The mosquito goes through four distinct stages during its life cycle: egg, larva,
pupa, and adult (see box). Larvicides kill insect larvae. Larvicides include
biological insecticides, such as the microbial larvicides Bacillus sphaericus and
Bacillus thuringiensis israelensis. Larvicides include other chemicals used for
controlling mosquito larvae, such as temephos, methoprene, oils, and
monomolecular films. Larvicide treatment of breeding habitats help reduce the
adult mosquito population in nearby areas.
larvicides are used as
one of several tools
in mosquito control
How are Larvicides Used in Mosquito Control?
State and local agencies in charge of mosquito control typically employ a variety
of techniques in an Integrated Pest Management (IPM) approach, which include
surveillance, source reduction, larviciding and adulticiding, to control mosquito
populations. Since mosquitoes must have water to breed, source reduction aims
to cut down opportunities for breeding, and can be as simple as turning over
trapped water in a container to large-scale engineering and management of marsh
water. Larviciding involves applying chemicals to habitats to kill pre-adult
mosquitoes. Larviciding can reduce overall pesticide usage in a control program
by reducing or eliminating the need for ground or aerial application of chemicals
to kill adult mosquitoes.
What are Microbial Larvicides?
microbial larvicides
are bacteria that are
registered as
pesticides
Mosquito Life Cycle
Microbial larvicides are bacteria that
egg - hatch when exposed to
are registered as pesticides for control
water;
of mosquito larvae in outdoor areas
such as irrigation ditches, flood water,
larva - (pl. - larvae) lives in the
standing ponds, woodland pools,
water; molts several times; most
pastures, tidal water, fresh or
species surface to breathe air;
saltwater marshes, and storm water
retention areas. Duration of
pupa - (pl. - pupae) non-feeding
effectiveness depends primarily on the
stage just prior to emerging as
mosquito species, the environmental
adult;
conditions, the formulation of the
adult - flies short time after
product, and water quality. Microbial
emerging and after its body
larvicides may be used along with
parts have hardened.
other mosquito control measures in an
integrated pest management (IPM)
program. The microbial larvicides
used for mosquito control are Bacillus
thuringiensis israelensis (Bti) and Bacillus sphaericus (Bs).
microbial larvicides
are harmful to insects
but not mammals
< Bacillus thuringiensis israelensis (Bti) is a naturally occurring soil bacterium
registered for control of mosquito larvae. Bti was first registered by EPA as
an insecticide in 1983. Mosquito larvae eat the Bti product which is made up
of the dormant spore form of the bacterium and an associated pure toxin. The
toxin disrupts the gut in the mosquito by binding to receptor cells present in
insects, but not in mammals. There are 25 Bti products registered for use in
the United States. Aquabac, Teknar, Vectobac, and LarvX are examples of
common trade names for the mosquito control products.
< Bacillus sphaericus is a naturally occurring bacterium that is found
throughout the world. Bacillus sphaericus was initially registered by EPA in
1991 for use against various kinds of mosquito larvae. Mosquito larvae
ingest the bacteria, and as with Bti, the toxin disrupts the gut in the mosquito
by binding to receptor cells present in insects, but not in mammals. VectoLex
CG and WDG are registered B. sphaericus products, and are effective for
approximately one to four weeks after application.
Do Microbial Larvicides Pose Risks to Human Health?
microbial larvicides
do not pose concerns
for human health or
the environment
when used according
to product labels
The microbial pesticides have undergone extensive testing prior to registration.
They are essentially nontoxic to humans, so there are no concerns for human
health effects with Bti, or B. sphaericus, when they are used according to label
directions.
Do Microbial Larvicides Pose Risks to Wildlife or the Environment?
Extensive testing shows that microbial larvicides do not pose risks to wildlife,
non-target species or the environment.
What is Methoprene?
methoprene is an
insect growth
regulator
Methoprene is a compound first registered by EPA in 1975 that mimics the action
of an insect growth regulating hormone and prevents the normal maturation of
insect larvae. It is applied to water to kill mosquito larvae and it may be used
along with other mosquito control measures in an IPM program. Altosid is the
name of the methoprene product used in mosquito control and is applied as
briquets (similar in form to charcoal briquets), pellets, sand granules, and liquids.
The liquid and pelletized formulations can be applied by helicopter and fixed-wing
aircraft.
Does Methoprene Pose Risks to Human Health?
methoprene used in
mosquito control
programs according
to label directions
does not pose
unreasonable risks to
human health or the
environment
Methoprene, used for mosquito control according to its label directions, does not
pose unreasonable risks to human health. In addition to posing low toxicity to
mammals, there is little opportunity for human exposure, since the material is
applied directly to ditches, ponds, marshes or flooded areas which are not
drinking water sources.
Does Methoprene Pose Risks to Wildlife or the Environment?
Methoprene used in mosquito control programs does not pose unreasonable risks
to wildlife or the environment. Toxicity of methoprene to birds and fish is low,
and it is nontoxic to bees. Methoprene breaks down quickly in water and soil, and
will not leach into groundwater. Methoprene is highly toxic to some species of
freshwater, estuarine, and marine invertebrates if misused. For that reason, EPA
has established specific precautions on the label to reduce such risks.
What is Temephos?
temephos is an
organophosphate
(OP)
temephos used
according to label
directions does not
pose unreasonable
risks
Temephos is an organophosphate (OP) pesticide registered by EPA in 1965, to
control mosquito larvae, and is the only organophosphate with larvicidal use. It is
an important resistance management tool for mosquito control programs; its use
helps prevent mosquitoes from developing resistance to the bacterial larvicides.
Temephos is used in areas of standing water, shallow ponds, swamps, marshes,
and intertidal zones. It may be used along with other mosquito control measures
in an integrated pest management (IPM) program. Abate is the trade name of the
temephos product used for mosquito control. Temephos is applied most
commonly by helicopter, but can be applied by backpack sprayers, fixed-wing
aircraft, and right-of-way sprayers in either liquid or granular forms.
Does Temephos Pose Risks to Human Health?
Temephos, applied according to the label for mosquito control, does not pose
unreasonable risks of human health effects. It is applied to water, and the amount
of temephos is very small in relation to the area covered, less than one ounce of
active ingredient per acre for the liquid and eight ounces per acre for
the granular formulations. Temephos breaks down within a few days in water
high dosages of OPs
can overstimulate the
nervous system
and post application exposure is minimal. However, at high dosages, temephos,
like other OPs, can overstimulate the nervous system causing nausea, dizziness,
confusion.
Does Temephos Pose Risks to Wildlife or the Environment?
temephos is toxic to
bees and it can be
toxic to some birds
and aquatic species if
misused
Because temephos is applied directly to water, it is not expected to have a direct
impact on terrestrial animals, but temephos can be highly toxic to some bird
species and aquatic organisms if misused, and it is toxic to bees. For that reason,
EPA has established specific precautions on the label to reduce such risks. The
registrant of temephos has submitted studies on toxicity to aquatic invertebrates,
which are being reviewed by EPA.
What is the Current Regulatory Status of Temephos?
EPA is currently
reviewing temephos
As part of its responsibility to reassess all older pesticides registered before 1984,
EPA is currently reviewing temephos as part of its reregistration process. The
review of temephos is scheduled for completion this calendar year. A risk
assessment covering all uses of temephos is available to the public on the EPA
web site. From the pesticide program home page (see address below), select
OPs, then select OP Schedule and Documents.
What are Monomolecular Films?
films drown larvae,
pupae and emerging
adults
Monomolecular films are chemicals that spread a thin film on the surface of the
water that makes it difficult for mosquito larvae, pupae and emerging adults to
attach to the waters surface, causing them to drown. Films may remain active for
typically 10-14 days on standing water, and have been used in the United States in
floodwaters, brackish waters, and ponds. They may be used along with other
mosquito control measures in an IPM program. They are also known under the
trade names Arosurf MSF and Agnique MMF.
Do Monomolecular Films Pose Risks to Human Health?
films do not pose a
risk to humans
Monomolecular films, used according to label directions for larva and pupa
control, do not pose a risk to human health. In addition to low toxicity, there is
little opportunity for human exposure, since the material is applied directly to
ditches, ponds, marshes or flooded areas which are not drinking water sources.
Do Monomolecular Films Pose Risks to Wildlife or the Environment?
films pose minimal
risks to the
environment
Monomolecular films, used according to label directions for larva and pupa
control, pose minimal risks to the environment. They do not last in the
environment for a long time, and are usually applied only to standing water, such
as roadside ditches, woodland pools, or containers which contain few non-target
organisms.
What are Oils?
oils form a coating
on the water to
drown mosquito
larvae, pupae and
emerging adults
Oils, like films, are used to form a coating on top of water to drown larvae, pupae
and emerging adult mosquitoes. They are specially derived from petroleum
distillates and have been used for many years in the U.S. to kill aphids on crops
and orchard trees, and to control mosquitoes. They may be used along with other
mosquito control measures in an IPM program. Trade names for oils used in
mosquito control are Bonide, BVA2, and Golden Bear-1111 (GB-1111).
Do Oils Pose Risks to Human Health?
oils do not pose a
risk to human health,
but may be toxic to
aquatic animals if
misapplied
Oils, used according to label directions for larva and pupa control, do not pose a
risk to human health. In addition to low toxicity, there is little opportunity for
human exposure, since the material is applied directly to ditches, ponds, marshes
or flooded areas which are not drinking water sources.
Do Oils Pose Risks to Wildlife or the Environment?
Oils, if misapplied, may be toxic to fish and other aquatic organisms. For that
reason, EPA has established specific precautions on the label to reduce such risks.
Where Can I get More Information About Larvicides
and Mosquito Control?
Centers for Disease
Control and
Prevention
For more information about mosquito control in your area, contact your state or
local health department. The federal Centers for Disease Control and Prevention
is also a source of information on disease control, and their Internet web site
includes a listing of state health departments. To contact the
Centers for Disease Control and Prevention (CDC):
Call: 970-221-6400
Fax: 970-221-6476
E-mail: dvbid@cdc.gov
web site: http://www.cdc.gov
national toll-free
pesticide hotline
mosquito control
professionals
federal pesticide
program office
Information on pesticides used in mosquito control can be obtained from the state
agency which regulates pesticides, or from the National Pesticide
Telecommunications Network (NPTN). The NPTN web site includes links to
all state pesticide regulatory agencies.
Toll-free hotline: 1-800-858-7378 (9:30 a.m. to 7:30 p.m. EST) daily except
holidays. Callers outside normal hours can leave a voice mail message, and
NPTN returns these calls the next business day.
E-mail: nptn@ace.orst.edu
web site: http://ace.orst.edu/info/nptn
Information on mosquito control programs can also be obtained from the
American Mosquito Control Association (AMCA) web site at:
http://www.mosquito.org. This site also lists many county mosquito agencies.
For more information regarding the federal pesticide regulatory programs,
contact:
EPA Office of Pesticide Programs (OPP)
Telephone: 703-305-5017
Fax: 703-305-5558
E-mail: opp-web-comments@epa.gov
web site: http://www.epa.gov/pesticides
EPAs 10 Regional Offices are also a source of pesticide information, as well as
on pesticide program activities in the individual regions.
10 EPA regional
offices
EPA Region I - CT, MA, ME, NH, RI, VT
888-372-7341
www.epa.gov/region01
EPA Region II - NJ, NY, PR, VI
732-321-4391
www.epa.gov/region02
EPA Region III - DE, DC, MD, PA, VA, WV
800-438-2474
EPA Region IV - AL, FL, GA, KY, MS, NC, SC, TN
800-241-1754
www.epa.gov/region4
EPA Region V - IL, IN, MI, MN, OH, WI
800-621-8431 (Region V only) or 312-353-2000
www.epa.gov/region5
7
EPA Region VI - AR, LA, NM, OK, TX
800-887-6063 (Region VI only) or 214-665-6444
www.epa.gov/region6
EPA Region VII - IA, KS, MO, NE
800-223-0425 or 913-551-7020
www.epa.gov/region7
EPA Region VIII - CO, MT, ND, SD, UT, WY
800-227-8917 (Region VIII only) or 303-551-7020
www.epa.gov/region08
EPA Region IX - AZ, CA, HI, NV, AS, GU
415-744-1500
www.epa.gov/region09
EPA Region X - AK, ID, OR, WA
800-424-4372 (Region X only) or 206-553-1200
www.epa.gov/r10earth
Other Helpful EPA Publications
For Your Information - How to Use Insect Repellents Safely
(735-F-93-052R)
For Your Information - Mosquitoes: How to Control Them
(735-F-98-003)
For Your Information - Naled for Mosquito Control
(735-F-00-003)
For Your Information - Malathion for Mosquito Control
(735-F-00-001)
For Your Information - Synthetic Pyrethroids for Mosquito Control
(735-F-00-004)
Questions and Answers - Pesticides and Mosquito Control
