Mosquitoes Are Insects Belonging to the Order Diptera, the True Flies

Methods of Mosquito Control

(Unless otherwise notated, all information provided by the American Mosquito Control Association)

IDENTIFICATION

Mosquitoes are insects belonging to the order Diptera, the True Flies. Like all True Flies, they have two wings, but unlike other flies, mosquito wings have scales. There are over 2500 different species of mosquitoes throughout the world; about 200 species occur in the United

States with 77 species occurring in Florida. A new species, Anopheles grabhamii, was reported

from the Florida Keys in 2001 (Darsie et al. 2002).

Mosquito adults are small, flying, midge-like insects. Female mosquitoes can be differentiated from similar insects by the presence of a long slender proboscis that is adapted for piercing skin and sucking blood, and long slender wings that are covered with small scales. Male mosquitoes have scale-covered wings, but their proboscis, or beaks, are shorter and thicker than the females’, and are adapted for sucking plant juices and other sources of sugar rather than blood. In the immature stages, called larvae or wigglers, mosquitoes are usually black or dark brown and occur in nonmoving or nearly still water. Most mosquito larvae have a distinctive siphon or air tube at the rear of their bodies. The next stage is the pupal stage; pupae, called tumblers, are also aquatic and are small, somewhat round forms, usually black in color.2

Mosquitoes can be an annoying, serious problem in man’s domain. They interfere with work and

spoil hours of leisure time. Their attacks on farm animals can cause loss of weight and decrease

milk production. Some mosquitoes are capable of transmitting diseases such as malaria, yellow

fever, dengue, filariasis, and encephalitis [St. Louis encephalitis (SLE), Western Equine

encephalitis (WEE), LaCrosse encephalitis (LAC), Japanese encephalitis (JE), Eastern Equine

LIFE CYCLE

The life cycles of mosquitoes vary widely from species to species. Some female mosquitoes lay

single eggs on water surfaces; others lay single eggs on moist soil where later flooding is likely.

Still other species lay batches of eggs, called rafts, 100 or more at a time on water surfaces. Eggs

deposited on water surfaces usually hatch within a day or so, but eggs laid on soil surfaces do not

hatch until flooding occurs, which may be months or even years later. Larvae, which are nearly

invisible to the naked eye, hatch from eggs. Larvae molt three times to become 4th-stage larvae.

Several days later, this larval form molts again to become a pupa. Adult mosquitoes emerge

from pupae 1 to 2 days after that, with male mosquitoes always emerging first. In summer, the

entire life cycle, from egg to adult, may be completed in a week or less.2

The mosquito goes through four separate and distinct stages of its life cycle: Egg, Larva, Pupa,

and Adult. Each of these stages can be easily recognized by its special appearance.

Egg: Eggs are laid one at a time or attached together to form “rafts.” They float on the surface

of the water. In the case of Culex and Culiseta species, the eggs are stuck together in rafts of up

to 200. Anopheles, Ochlerotatus and Aedes, as well as many other genera, do not make egg

rafts, but lay their eggs singly. Culex, Culiseta, and Anopheles lay their eggs on the water

surface while many Aedes and Ochlerotatus lay their eggs on damp soil that will be flooded by

water. Most eggs hatch into larvae within 48 hours; others might withstand subzero winters

before hatching. Water is a necessary part of their habitat.

Larva: The larva (plural - larvae) lives in the water and comes to the surface to breathe. Larvae

shed (molt) their skins four times, growing larger after each molt. Most larvae have siphon tubes

for breathing and hang upside down from the water surface. Anopheles larvae do not have a

siphon and lie parallel to the water surface to get a supply of oxygen through a breathing

opening. Coquillettidia and Mansonia larvae attach to plants to obtain their air supply. The

Pupa: The pupal stage is a resting, non-feeding stage of development, but pupae are mobile, responding to light changes and moving (tumble) with a flip of their tails towards the bottom or protective areas. This is the time the mosquito changes into an adult. This process is similar to the metamorphosis seen in butterflies when the butterfly develops - while in the cocoon stage - from a caterpillar into an adult butterfly. The Culex species takes about two days to do this during summer in the southern United States. When development is complete, the pupal skin splits and the adult mosquito (imago) emerges.

Adult: The newly emerged adult rests on the surface of the water for a short time to allow itself to dry and all its body parts to harden. The wings have to spread out and dry properly before it can fly. Blood feeding and mating does not occur for a couple of days after the adults emerge.

How long each stage lasts depends on both temperature and species characteristics. For instance,

Culex tarsalis, a common California mosquito, might go through its life cycle in 14 days at 70° F and take only 10 days at 80° F. On the other hand, some species have naturally adapted to go through their entire life cycle in as little as four days or as long as one month.

MOSQUITO EGG RAFT

Many mosquitoes, such as Culex quinquefasciatus, lay their eggs on the surface of fresh or

stagnant water. The water may be in tin cans, barrels, horse troughs, ornamental ponds,

swimming pools, puddles, creeks, ditches, catch basins, or marshy areas. Mosquitoes prefer

water sheltered from the wind by grass and weeds.

Culex mosquitoes usually lay their eggs at night over a period of time sticking them together to

form a raft of from 100 to 300 eggs. A raft of eggs looks like a speck of soot floating on the

water and is about 1/4 inch long and 1/8 inch wide. A female mosquito may lay a raft of eggs

every third night during its life span.

Anopheles and many other mosquitoes lay their eggs singly on the water surface. Aedes and

Ochlerotatus mosquitoes lay their eggs singly, usually on damp soil. Aedes and Ochlerotatus

eggs are more resistant to drying out (some require complete drying out before the eggs will

hatch) and hatch only when flooded with water (salt water high tides, irrigated pastures, treeholes

flooded by rains, flooded stream bottoms). Anopheles, Culex, and Mansonia eggs are

susceptible to long periods of drying out.

Tiny mosquito larvae (1st instar) emerge from the eggs within 24 - 48 hours almost in unison.

MOSQUITO LARVA

Mosquito larvae, commonly called “wigglers,” live in water from 4 to 14 days depending on water temperature.

Larvae must come to the surface at frequent intervals to obtain oxygen through a breathing tube

called a siphon. They are constantly feeding since maturation requires a huge amount of energy

and food. They hang with their heads down and the brushes by their mouths filtering anything

small enough to be eaten toward their mouths to nourish the growing larvae. They feed on algae,

© 2014 All Star Training, Inc. 4 plankton, fungi, bacteria, and other microorganisms. They breath at the water surface with the breathing tube up breaking the water surface tension. One mosquito species larva feeds on larvae of other mosquitoes: Toxorhynchites, the largest mosquito known, are predators of other mosquito larvae sharing their habitat. Their larvae are much larger than other mosquito larvae.

During growth, the larva molts (sheds its skin) four times. The stages between molts are called instars. At the fourth instar, the usual larva reaches a length of almost 1/2 inch and toward the end of this instar ceases feeding. When the fourth instar larva molts, it becomes a pupa.

MOSQUITO PUPA

Mosquito pupae, commonly called “tumblers,” live in water from 1 to 4 days, depending upon species and temperature.

The pupa is lighter than water and therefore floats at the surface. It takes oxygen through two breathing tubes called “trumpets.” The pupa does not eat, but it is not an inactive stage. When disturbed, it dives in a jerking, tumbling motion toward protection and then floats back to the surface.

The metamorphosis of the mosquito into an adult is completed within the pupal case. The adult mosquito splits the pupal case and emerges to the surface of the water where it rests until its body dries and hardens.

MOSQUITO ADULT

Only female mosquitoes require a blood meal and bite animals – warm or cold-blooded – and birds. Stimuli that influence biting (blood feeding) include a combination of carbon dioxide, temperature, moisture, smell, color, and movement. Male mosquitoes do not bite, but feed on the nectar of flowers or other suitable sugar source. Acquiring a blood meal (protein) is essential for egg production, but mostly both male and female mosquitoes are nectar feeders. Female

Toxorhynchites actually can’t obtain a bloodmeal and are restricted to a nectar diet. Of those © 2014 All Star Training, Inc. 5 female mosquitoes capable of blood feeding, human blood meals are seldom first or second choices. Horses, cattle, smaller mammals, and/or birds are preferred.

Aedes and Ochlerotatus mosquitoes are painful and persistent biters. They search for a blood meal early in the morning, at dusk (crepuscular feeders) and into the evening. Some are diurnal

(daytime biters) especially on cloudy days and in shaded areas. They usually do not enter dwellings, and they prefer to bite mammals like humans. Aedes and Ochlerotatus mosquitoes are strong fliers and are known to fly many miles from their breeding sources.

Culex mosquitoes are painful and persistent biters also, but prefer to attack at dusk and after dark. They readily enter dwellings for blood meals. Domestic and wild birds usually are preferred over man, cows, and horses. Culex nigripalpus is known to transmit St. Louis encephalitis to man in Florida. Culex mosquitoes are generally weak fliers and do not move far from home, although they have been known to fly up to two miles. Culex usually live only a few weeks during the warm summer months. Those females that emerge in late summer search for sheltered areas where they “hibernate” until spring. Warm weather brings them out again in search of water on which to lay their eggs.

Culiseta mosquitoes are moderately aggressive biters, attacking in the evening hours or in the shade during the day. Psorophora, Coquillettidia, and Mansonia mosquitoes are becoming more pestiferous as an ever-expanding human population invades their natural habitats. Anopheles mosquitoes are persistent biters and are the only mosquitoes which transmit malaria to man.

MOSQUITO-BORNE DISEASES

Female mosquitoes of nearly all species require blood from vertebrate animals to develop eggs, and many species bite people, pets, and livestock for this purpose. The most important consequence of this is the transmission of microorganisms that cause diseases. Mosquitoes cause more human suffering than any other organism - over one million people die from

mosquito-borne diseases every year. Not only can mosquitoes carry diseases that afflict humans,

they also transmit several diseases and parasites to which dogs and horses are very susceptible.

These include dog heartworm, West Nile virus (WNV), and Eastern equine encephalitis (EEE).

In addition, mosquito bites can cause severe skin irritation through an allergic reaction to the

mosquito’s saliva - this is what causes the red bump and itching. Mosquito vectored diseases

include protozoan diseases, i.e., malaria, filarial diseases such as dog heartworm, and viruses

such as dengue, encephalitis, and yellow fever. CDC Travelers’ Health provides information on

travel to destinations where human-borne diseases might be a problem.

3 METHODS OF MOSQUITO CONTROL

Methods used by federal, state, and local agencies in mosquito control (information provided by

the Environmental Protection Agency unless otherwise notated).

The first step in mosquito control is surveillance. State or local mosquito specialists conduct

surveillance for diseases harbored by domestic and nonnative birds, including sentinel chickens

(used as virus transmission indicators), and mosquitoes. State and local mosquito control

authorities also conduct surveillance for larval habitats by using maps and aerial photographs,

and by evaluating larval populations. Other techniques include various light traps, biting counts,

and analysis of reports from the public.

Mosquito control programs also put high priority on trying to prevent a large population of adult

mosquitoes from developing so that additional controls may not be necessary. Since mosquitoes

must have water to breed, methods of prevention may include:

• controlling water levels in lakes, marshes, ditches, or other mosquito breeding sites;

• eliminating small breeding sites if possible;

• stocking bodies of water with fish species that feed on larvae.

Both chemical and biological measures may be employed to kill immature mosquitoes during

larval stages.

Chemical or Biological Measures to Control Mosquitoes

Controlling mosquitoes at the larval stage

Larvicides target larvae in the breeding habitat before they can mature into adult mosquitoes and

disperse. Larvicides include:

Bacterial Insecticides

• Bacillus thuringiensis israelensis

• Bacillus sphaericus

Insect Growth Inhibitor

• Methoprene

Organophosphate Insecticide

• Temephos

Other Materials

• Mineral oils

• Monomolecular films

Oils and films disperse as a thin layer on the surface of the water, which cause larvae and pupae

to drown. Liquid larvicide products are applied directly to water using backpack sprayers and

truck or aircraft-mounted sprayers. Tablet, pellet, granular, and briquet formulations of

larvicides are also applied by mosquito controllers to breeding areas.

Controlling Adult Mosquitoes

Adult mosquito control may be undertaken to combat an outbreak of mosquito-borne disease or a

are known as adulticides and are applied either by aircraft or on the ground employing

truck-mounted sprayers. State and local agencies commonly use the organophosphate insecticides malathion and naled and the synthetic pyrethroid insecticides permethrin, resmethrin, and sumithrin for adult mosquito control.

Mosquito adulticides are applied as ultra-low volume (ULV) sprays. ULV sprayers dispense

very fine aerosol droplets that stay aloft and kill flying mosquitoes on contact. ULV applications

involve small quantities of pesticide active ingredient in relation to the size of the area treated,

typically less than 3 ounces per acre, which minimizes exposure and risks to people and the

environment.

Adulticides can be used for public health mosquito control programs without posing

unreasonable risks to the general population or to the environment when applied according to the

pesticide label.

The Environmental Protection Agency (EPA) evaluates and registers (licenses) pesticides to

ensure that they can be used safely. These pesticides include products used in the mosquito

control programs that 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 percent 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 IS MALATHION?

Malathion is an organophosphate (OP) insecticide that has been registered for use in the United

States since 1956. It is used in agriculture, residential gardens, public recreation areas, and in

public health pest control programs. When applied in accordance with the rate of application and

safety precautions specified on the label, malathion can be used to kill mosquitoes without

posing unreasonable risks to human health or the environment.

How is Malathion Used in Mosquito Control?

The mosquito goes through four distinct stages during its life cycle: egg, larva, pupa, and adult.

Malathion is an adulticide, used to kill adult mosquitoes. In mosquito control programs

conducted by state or local authorities, malathion is applied by truck-mounted or

aircraft-mounted sprayers. Malathion is applied as an ultra-low volume (ULV) spray. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill mosquitoes on contact. ULV applications involve small quantities of pesticide active ingredient in relation to the size of the area treated. For mosquito control, malathion is applied at a maximum rate of 0.23 pounds (or about 2.5 fluid ounces) of active ingredient per acre, which minimizes exposure and risks to people and the environment.

Does Malathion Pose Risks to Human Health?

Malathion can be used for public health mosquito control programs without posing unreasonable

risks to the general population when applied according to the label. EPA has estimated the

exposure and risks to both adults and children posed by ULV aerial and ground applications of

malathion. Because of the very small amount of active ingredient released per acre of ground,

the estimates found that for all scenarios considered, exposures were several times below an

amount that might pose a health concern. These estimates assumed that a toddler would ingest

some soil and grass in addition to skin and inhalation exposure. However, at high doses,

malathion, like other organophosphates, can over-stimulate the nervous system causing nausea, dizziness, or confusion. Severe high-dose poisoning with any organophosphate can cause convulsions, respiratory paralysis, and death.

Does Malathion Pose Risks to Wildlife or the Environment?

Malathion used in mosquito control programs does not pose unreasonable risks to wildlife or the environment. Malathion degrades rapidly in the environment, especially in moist soil, and it displays low toxicity to birds and mammals. Malathion is highly toxic to insects, including

beneficial insects such as honeybees. For that reason, EPA has established specific precautions

on the label to reduce such risks.

What is the Current Regulatory Status of Malathion?

As part of its responsibility to reassess all older pesticides registered before 1984, EPA is

currently reviewing malathion as part of its re-registration process. The review of malathion is scheduled for completion in 2006. A risk assessment covering all uses of malathion is currently available to the public for review at http://www.epa.gov/oppsrrd1/op/malathion.htm. Visit the

EPA Web site (see address below) for the most current information on malathion.

What is Malaoxon and Does it Pose Risks to Human Health?

EPA’s most recent analysis of toxicity data for malathion received since 2000 shows that its risk characterization remains generally unchanged. However, EPA has also refined its characterization of the potential risk from malaoxon, a more toxic compound that is formed from malathion under certain conditions. For example, malathion runoff and spray drift may reach drinking water sources downstream from where the malathion was used. Malathion present in untreated water will form malaoxon during the chlorination process in water treatment facilities.

Malaoxon can also form more slowly when malathion is deposited on hard, dry surfaces and exposed to air over time. The Agency’s assessment shows that, even when considering the presence of malaoxon on surfaces following applications of malathion for mosquito control, the relatively low application rates and small droplet sizes used in these types of applications result in minimal exposure to people in the treated area.

WHAT ARE LARVICIDES?

Larvicides kill mosquito larvae. Larvicides include biological insecticides, such as the microbial larvicides Bacillus sphaericus and Bacillus thuringiensis israelensis. Larvicides include other pesticides, such as temephos, methoprene, oils, and monomolecular films. Larvicide treatments of breeding habitats help reduce the adult mosquito population in nearby areas.

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) program. An IPM approach includes surveillance, source reduction, larviciding and adulticiding to control mosquito populations. Since mosquitoes must have water to breed, source reduction can be as simple as turning over trapped water in a container to undertaking large-scale engineering and management of marsh water levels. Larviciding involves applying pesticides to breeding habitats to kill mosquito larvae. Larviciding can reduce overall pesticide usage in a control program. Killing mosquito larvae before they emerge as adults

can reduce or eliminate the need for ground or aerial application of pesticides to kill adult mosquitoes.

What are Microbial Larvicides?

Microbial larvicides are bacteria that are registered as pesticides for control of mosquito larvae in outdoor areas such as irrigation ditches, flood water, standing ponds, woodland pools, pastures, tidal water, fresh or saltwater marshes, and storm water retention areas. Duration of effectiveness depends primarily on the mosquito species, the environmental conditions, the formulation of the product, and water quality. Microbial larvicides may be used along with other mosquito control measures in an IPM program. The microbial larvicides used for mosquito control are Bacillus thuringiensis israelensis (Bti) and Bacillus sphaericus (B. sphaericus).

Bacillus thuringiensis israelensis 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 that 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 26 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. B. 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.

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, when used according to label directions.

WHAT IS METHOPRENE?

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 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 that 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 ground water.

Methoprene mosquito control products present minimal acute and chronic risk to freshwater fish, freshwater invertebrates, and estuarine species.

WHAT IS TEMEPHOS?

Temephos is an organophosphate (OP) pesticide registered by EPA in 1965 to control mosquito

larvae, and it 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 inter-tidal zones. It may be used along with other mosquito control measures in an 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 form.

Does Temephos Pose Risks to Human Health?

Temephos, applied according to the label for mosquito control, does not pose unreasonable risks to human health. It is applied to water, and the amount of temephos is very small in relation to the area covered, less than 1 ounce of active ingredient per acre for the liquid and 8 ounces per acre for the granular formulations. Temephos breaks down within a few days in water, and post-application exposure is minimal. However, at high dosages, temephos, like other OPs, can over-stimulate the nervous system causing nausea, dizziness, and confusion.

Does Temephos Pose Risks to Wildlife or the Environment?

Because temephos is applied directly to water, it is not expected to have a direct impact on terrestrial animals or birds. Current mosquito larviciding techniques pose some risk to non-target aquatic species and the aquatic ecosystem. Although temephos presents relatively low risk to birds and terrestrial species, available information suggests that it is more toxic to aquatic invertebrates than alternative larvicides. For this reason, EPA is limiting temephos use to areas where less-hazardous alternatives would not be effective, specifying intervals between applications, and limiting the use of high application rates. © 2014 All Star Training, Inc. 15

What is the Current Regulatory Status of Temephos?

As part of its responsibility to reassess all older pesticides registered before 1984, EPA completed its revised risk assessments for temephos in July 2001, and has issued risk management decisions in the final re-registration eligibility decision (RED). The RED document is available on the EPA Web site at: www.epa.gov/oppsrrd1/REDs/temephos_red.htm.

WHAT ARE MONOMOLECULAR FILMS?

Monomolecular films are low-toxicity pesticides 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 water’s surface, causing them to drown. Films may remain active typically for 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?

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 that are not drinking water sources.

Do Films Pose Risks to Wildlife or the Environment?

Monomolecular films, used according to label directions for larva and pupa control, pose minimal risks to the environment. They do not last very long in the environment, and are usually applied only to standing water, such as roadside ditches, woodland pools, or containers that contain few non-target organisms.

WHAT ARE OILS?

Oils, like films, are pesticides 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 United States 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, 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 that 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.

WHAT IS NALED?

Naled is an organophosphate (OP) insecticide that has been registered since 1959 for use in the

United States. It is used primarily for controlling adult mosquitoes, but naled is also used on

food and feed crops, and in greenhouses. When applied in accordance with the rate of

application and the safety precautions specified on the label, naled can be used to kill mosquitoes

without posing unreasonable risks to human health or the environment.

How is Naled Used in Mosquito Control?

Naled is an adulticide used to kill adult mosquitoes. In mosquito control programs conducted by

state or local authorities, naled is applied by truck-mounted or aircraft-mounted sprayers. Naled

is applied as an ultra-low volume (ULV) spray. ULV sprayers dispense very fine aerosol

© 2014 All Star Training, Inc. 17 droplets that stay aloft and kill mosquitoes on contact. ULV applications involve small quantities of pesticide active ingredient in relation to the size of the area treated. For mosquito control, the maximum rate for ground and aerial application is 0.1 lb of active ingredient per acre, which minimizes exposure and risks to people and the environment.

Does Naled Pose Risks to Human Health?

Naled can be used for public health mosquito control programs without posing unreasonable risks to the general population when applied according to the label. EPA has estimated the exposure and risks to both adults and children posed by ULV aerial and ground applications of naled. Because of the very small amount of active ingredient released per acre of ground, the estimates found that for all scenarios considered, exposures were hundreds or even thousands of times below an amount that might pose a health concern. These estimates assumed several spraying events over a period of weeks, and assumed that a toddler would ingest some soil and grass in addition to skin and inhalation exposure. However, at high doses, naled like other organophosphates, can over-stimulate the nervous system causing nausea, dizziness, or confusion. Severe high-dose poisoning with any organophosphate can cause convulsions, respiratory paralysis, and death.

Does Naled Pose Risks to Wildlife or the Environment?

Naled used in mosquito control programs does not pose unreasonable risks to wildlife or the environment. Naled degrades rapidly in the environment, and it displays low toxicity to birds and mammals. Acute and chronic risk to fish is not expected, but there is potential for risks to invertebrates from the repeated use of naled. Naled is highly toxic to insects, including beneficial insects such as honeybees. For that reason, EPA has established specific precautions on the label to reduce such risk.

What is the Current Regulatory Status of Naled?

As part of its responsibility to reassess all older pesticides registered before 1984, EPA is

currently reviewing naled as part of its re-registration process. The review of naled is scheduled

for completion in 2002. A risk assessment covering all uses of naled is available to the public on

the EPA Web site at http://www.epa.gov/oppsrrd1/op/naled.htm

WHAT ARE SYNTHETIC PYRETHROIDS?

Pyrethroids are synthetic chemical insecticides that act in a similar manner to pyrethrins, which

are derived from chrysanthemum flowers. Pyrethroids are widely used for controlling various

insects. Permethrin, resmethrin, and sumithrin are synthetic pyrethroids commonly used in

mosquito control programs to kill adult mosquitoes.

• Permethrin has been registered by EPA since 1977. It is currently registered and sold in a

number of products such as household insect foggers and sprays, tick and flea sprays for yards,

flea dips and sprays for cats and dogs, termite treatments, agricultural and livestock products,

and mosquito abatement products.

• Resmethrin has been registered by EPA since 1971 and is used to control flying and crawling

insects in the home, lawn, garden, and industrial sites. It can also be used to control insects on

ornamental plants (outdoor and greenhouse use), on pets and horses, and as a mosquitocide.

Because of its toxicity to fish, resmethrin is a Restricted Use Pesticide (RUP) that is available for

use only by certified pesticide applicators or persons under their direct supervision.

• Sumithrin has been registered by EPA since 1975 and is used to control adult mosquitoes and as

an insecticide in transport vehicles such as aircraft, ships, railroad cars, and truck trailers. It is

also used as an insecticide and miticide in commercial, industrial, and institutional nonfood

areas, in homes and gardens, in greenhouses, and in pet quarters and on pets.

How are Synthetic Pyrethroids Used in Adult Mosquito Control?

Most pyrethroid mosquito control products can be applied only by public health officials and trained personnel of mosquito control districts. Mosquito control professionals apply pyrethroids as an ultra low volume (ULV) spray. ULV sprayers dispense very fine aerosol droplets that stay aloft and kill adult mosquitoes on contact. Pyrethroids used in mosquito control are typically mixed with a synergist compound, such as piperonyl butoxide, which enhances the effectiveness of the active ingredient. The product is often diluted in water or oil and applied at rates less than

1/100th of a pound of active ingredient or less than 4 fluid ounces of mixed formulation per acre.

Do Pyrethroids Pose Risks to Human Health?

Pyrethroids can be used for public health mosquito control programs without posing unreasonable risks to human health when applied according to the label. Pyrethroids are considered to pose slight risks of acute toxicity to humans, but at high doses, pyrethroids can affect the nervous system.

Do Pyrethroids Pose Risks to Wildlife or the Environment?

Pyrethroids used in mosquito control programs do not pose unreasonable risks to wildlife or the environment. Pyrethroids, when applied at mosquito control rates, are low in toxicity to mammals, and are practically nontoxic to birds. Mosquito control formulations of permethrin break down in the environment, and high temperatures and sunlight accelerate this process.

However, pyrethroids are toxic to fish and to bees. For that reason, EPA has established specific precautions on the label to reduce such risks, including restrictions that prohibit the direct application of products to open water or within 100 feet of lakes, streams, rivers, or bays.

What is The Current Regulatory Status of Pyrethroids?

As part of its responsibility to reassess all pesticides registered before 1984, EPA has given highest priority to reviewing more acutely toxic pesticides such as organophosphates and carbamates. Organophosphates are currently under review.

WHAT PROPERTY OWNERS CAN DO TO CONTROL MOSQUITOES

LARVAL CONTROL

Controlling mosquitoes, and exposure to diseases they may carry, can be done by chemical and

non-chemical methods. The first line of defense begins at home.

1. Remove their habitat (where they live and breed)

• Eliminate standing water in rain gutters, old tires, buckets, plastic covers, toys, or any other

container where mosquitoes can breed.

• Drain or fill temporary pools of water with dirt.

• Keep swimming pool water treated and circulating.

• Destroy or dispose of tin cans, old tires, buckets, unused plastic swimming pools, or other

containers that collect and hold water. Do not allow water to accumulate in the saucers of

flowerpots, cemetery urns or in pet dishes for more than 2 days.

• Check for trapped water in plastic or canvas tarps used to cover boats, pools, etc. Arrange the

tarp to drain the water.

• Clean debris from rain gutters and remove any standing water under or around structures, or on

flat roofs. Check around faucets and air conditioner units and repair leaks or eliminate puddles

that remain for several days.

• Change the water in birdbaths and wading pools at least once a week and stock ornamental pools

with top feeding predacious minnows. Known as mosquito fish, these minnows are about 1 to

1½ inches in length and can be purchased or native fish can be seined from streams and creeks

locally. Ornamental pools may be treated with biorational larvicides [Bacillus thuringiensis

subsp. israelensis (Bti) or S-methoprene (IGR) containing products] under certain circumstances.

Commercial products “Mosquito Dunks” and “Mosquito Bits” containing Bti can be purchased

at many hardware/garden stores for homeowner use. Zodiac, a division of Wellmark

International, has developed Pre-Strike Preventative Mosquito Control (PMC) product that kills

developing mosquitoes using insect growth regulator (IGR) technology. Like Mosquito Dunks,

Zodiac’s Pre-Strike can be found at many home/garden and pet specialty stores.

• Fill or drain puddles, ditches and swampy areas, and either remove, drain, or fill tree holes and

stumps with mortar. These areas may be treated with Bti or methoprene products also.

• Eliminate seepage from cisterns, cesspools, and septic tanks.

• Eliminate standing water around animal watering troughs. Flush livestock water troughs twice a

week.

• Check around construction sites or do-it-yourself improvements to ensure that proper backfilling

and grading prevent drainage problems.

• Irrigate lawns and gardens carefully to prevent water from standing for several days.

• If ditches do not flow and contain stagnant water for one week or longer, they can produce large

numbers of mosquitoes. Report such conditions to a Mosquito Control or Public Health Office.

Do not attempt to clear these ditches because they may be protected by wetland regulations.

2. Prevent your exposure to mosquitoes

• Use EPA-registered mosquito repellents when necessary and follow label directions and

precautions closely.

• Use head nets, long sleeves, and long pants if you venture into areas with high mosquito

populations, such as salt marshes.

• If there is a mosquito-borne disease warning in effect, stay inside during the evening when

mosquitoes are active.

• Make sure window and door screens are “bug tight.”

• Replace your outdoor lights with yellow “bug” lights that tend to attract fewer mosquitoes than

ordinary lights. The yellow lights are NOT repellents, however.

The most effective control methods are those targeted against the larval stage. Keep in mind,

however, that mosquitoes can migrate several miles from where they develop. Even successful

control of mosquito larvae on your premises may not result in reducing mosquito numbers or

biting activity.2

Mosquito Fish. The mosquito fish, Gambusia affinis, has been used worldwide for mosquito

control. These fish are most effectively used in man-made bodies of water that do not connect

with natural waters. They can be obtained from most vector control districts.2

Bacillus thuringiensis subsp. israelensis. The bacterium Bacillus thuringiensis subsp.

israelensis infects and kills mosquito larvae. It must be consumed by the larvae and acts as a

stomach poison, damaging mid-gut cells of mosquito larvae. It is highly selective, killing only

mosquitoes and larvae of a few other related flies. This pesticide is marketed in a variety of

formulations for the homeowner, the most common being the Mosquito Dunk, a donut-shaped

float that lasts for about 30 days in water.2

Outdoor Sprays. The use of insecticide sprays or outdoor foggers for control of adult

mosquitoes is one option available. This option has its limitations in that while it may provide a

temporary reduction of the adult population, which can be useful if the application is made

shortly before a backyard picnic or family gathering, it has no lasting effect. Equipment for the

application of outdoor sprays is expensive and complex.2

ADULT CONTROL

Mosquito Traps. Insect electrocutors (bug zappers) and mosquito trapping devices are 20th century control measures. Manufacturers modernized 19th century mosquito trapping devices such as the New Jersey light trap with more “bells and whistles” to improve their appeal to the public. Insect electrocuter light traps have been extensively marketed for the past several years claiming they can provide relief from the biting mosquitoes and other pests in your back yard.

Numerous devices are available for purchase that claim to attract, repel or kill outdoor infestations of mosquitoes. They should be thoroughly researched before being purchased.

Other mosquito traps are designed to mimic a mammal (horse, cattle, man and domestic pets) by emitting a plume of carbon dioxide, heat, and moisture, which is often combined with an additional attractant, i.e., octenol, to create an attractant to mosquitoes, no-see-ums, biting midges, and black flies. After drawing the insects to the trap, a vacuum device sucks the insects into a net or cylinder where they dehydrate and die. No electric killing grid or pesticides are used.

Scientific data relative to the effectiveness of these devices is sparse so be sure to review all the information available before purchasing one. In addition, some of the mosquito traps are quite expensive.

Space sprays. Mosquitoes used to be killed inside the house by using a flit gun. Household aerosol space sprays containing synergized pyrethrum or synthetic pyrethroids (allethrin, resmethrin, etc.) are available now. The major advantage of space treatment is immediate knockdown, quick application, and relatively small amounts of materials required for treatment.

Space sprays are most effective indoors. Outdoors, the insecticide particles disperse rapidly and may not kill many mosquitoes. The major disadvantage of space spraying is that it will not manage insects for long periods of time.

Only insecticides labeled for flying insect management should be sprayed into the air. Best

results are obtained if doors and windows are kept closed during spraying and for 5-10 minutes after spraying. Always follow directions on the label.

Outdoor Control. Homeowners, ranchers, or businesses may use hand-held ULV foggers, portable or fogging attachments for tractors or lawn mowers for temporary relief from flying mosquitoes. Pyrethrins or 5% malathion can be fogged outdoors. Follow instructions on both the insecticide label and fogging attachments for application procedure.

Mechanical Barriers. Mosquitoes can be kept out of the home by keeping windows, doors, and porches tightly screened (16-18 mesh). Those insects that do get into structures can be eliminated with a fly swatter or an aerosol space spray containing synergized pyrethrum.

Vegetation Management. Adult mosquitoes prefer to rest on weeds and other vegetation.

Homeowners can reduce the number of areas where adult mosquitoes can find shelter by cutting down weeds adjacent to the house foundation and in their yards, and mowing the lawn regularly.

To further reduce adult mosquitoes harboring in vegetation, insecticides may be applied to the lower limbs of shade trees, shrubs, and other vegetation. Products containing allethrin, malathion or carbaryl have proven effective. Paying particular attention to shaded areas, apply the insecticides as coarse sprays onto vegetation, walls, and other potential mosquito resting areas using a compressed air sprayer. Always read and follow label directions before using any pesticide.

Many of the mosquito problems that trouble homeowners and the general population cannot be eliminated through individual efforts, but instead, must be managed through an organized effort.

Many states have some sort of organized mosquito control, either at the State, County or city level. Florida has over 50 organized mosquito control organizations that specialize in area mosquito control. Some residential communities organize to control their mosquito problems.

There has been an increase in the number of these organizations in the United States since the

West Nile arbovirus outbreak in 1999. These organized management programs incorporate the

IMM strategies mentioned above which include permanent and temporary measures. Permanent

measures include impounding water and ditching, and draining swampy mosquito breeding

areas. Temporary measures include treating breeding areas to kill larvae and aerosol spraying

(ULV) by ground or aerial equipment to kill adult and larval mosquitoes. If you live within an

organized mosquito management district, support it in its control efforts. Organized mosquito

management can accomplish much more than individual efforts. If you are not sure about

whether your community has a mosquito control district, contact the local division of health

officials.

Aerial adult mosquito control using fixed-wing aircraft or helicopters and/or ground adult

mosquito control using truck or boat mounted equipment are often the most visual aspects of an

organized mosquito control program. This method of control is called adulticing. Although it is

often expensive in terms of manpower, equipment and inventory, sometimes difficult to

accomplish and more likely to affect non-target organisms if mishandled, it is the only method to

rapidly reduce infected mosquito numbers or to control pest and nuisance mosquitoes from

inaccessible breeding areas that are interfering with normal outdoor activities of a community.

2 ERSONAL PROTECTION

Probably the most effective method of personal protection from mosquito bites is to avoid places

where mosquito densities are high and to avoid being out-of-doors at times of the day when mosquito activity is at its highest. In mountainous areas, most species of mosquitoes bite during the morning and afternoon hours and often not at all during periods of darkness. In some low elevation areas, such as the Central Valley, some mosquitoes tend to bite at night, while others bite during the day. The dominant mosquito species in an area depends on the location in the state; it is good to learn the activity patterns of the mosquitoes in your area. © 2014 All Star Training, Inc. 26

Repellents. If you find yourself in a situation where you must be exposed to biting mosquitoes,

there are several things you can do. First, minimize the exposed skin surface by wearing a hat or

head net, long trousers, and a long-sleeved shirt. Some mosquitoes will bite through lightweight clothing, but the number of bites received is definitely reduced if most areas of the body are covered. When mosquito densities become very high, you may want to apply a mosquito repellent. Most effective repellents contain DEET (N,N-diethyl-meta-toluamide). Commercial repellents contain varying concentrations of DEET, usually between 10 and 50%. DEET is an irritant to some people and it may damage synthetic materials such as clothing or plastics.

Special formulations for children contain low concentrations of DEET in an oil-based medium that slowly releases the compound and limits its absorption through the skin; these formulations also work well for adults. The insecticide permethrin functions as a repellent when it is applied to clothing; it should not be used directly on the skin. Repellents have their drawbacks: they are effective only for about 4 hours or less depending on wind, high temperature, high humidity, and sweating. When applying DEET, thoroughly apply the material to all exposed skin, including behind the ears.

If you wish to avoid DEET, there are few, if any, effective alternatives. Plant oils such as those from birch, bluestem grass, geranium, pine, rosemary, spearmint, yarrow, lantana, and neem have been shown to be somewhat repellent to mosquitoes, but most are not available in commercial mosquito repellents.

Some body lotions such as Avon Skin-So-Soft offer a degree of protection from mosquito bites at least in part by forming an oily film on the skin’s surface that prevents the insect’s mouthparts from penetrating. Materials that form protective layers on the skin must be reapplied frequently.

Other Repellents. There is a vast array of other products marketed to repel mosquitoes, most of which are ineffective. These include wristbands that contain an aromatic repellent, ultrasonic

emitters, electric grids, electronic repellers, aromatic plants (the most common one is the

so-called mosquito plant, Pelargonium x citrosum), incense coils, vitamins (B), and mixtures of brewer’s yeast and garlic. Researchers have shown that all these methods are of little or no value in repelling mosquitoes. Oil of citronella, which is extracted from Andropogon nardus, has long been claimed to repel mosquitoes. Burning citronella candles or mosquito coils works best if

there is relatively little air movement, but these products are only for use outdoors, which makes

them mostly worthless. Electric bug zappers that are used to kill pest insects are probably

counterproductive because many of the insects caught by these traps are those that prey on

mosquitoes.

MISTAKEN IDENTITIES

Insects Commonly Mistaken for Mosquitoes (following information provided by the AMCA)

CRANE FLIES (Tipulidae)

Crane Flies are delicate insects varying in size from ¼ inch to as large as 1½ inches in length.

The largest crane flies are sometimes called “daddy-long-legs,” “gully nippers,” or “mosquito hawks.” However, they do not bite people and they do not eat mosquitoes. Some species of crane flies emerge from aquatic sources and others from terrestrial or decaying vegetation sources. Crane flies are not predacious and usually many times larger than a typical mosquito.

Adults are strongly attracted to porch lights. The larvae live in loose soil or organic matter and

feed on the roots of plants.

MAYFLIES (Ephemeroptera)

Mayflies can be quite abundant near creeks, flood control channels, and other water sources

throughout the United States. Their larvae are found in most aquatic habitats and can live in

moving water. Adult mayflies are recognized by the way they hold their wings at rest and the presence of two or three long “caudal” filaments at the tip of the abdomen. Though not even

© 2014 All Star Training, Inc. 28 closely resembling mosquitoes, their seasonal occurrence at porch lights and on the walls of buildings near their aquatic breeding sources invariably attracts the attention of some concerned residents. The nymphs of mayflies develop in all types of aquatic habitats where they form an important part of the food chain. Adults are among the most short lived in the insect world.

They generally survive hours to a few days after emergence in order to mate and lay eggs. Huge swarms of adult mayflies, in recent years (1995-97), have become a nuisance by their presence in some communities along the western basin of Lake Erie. Most swarming occurs in late June and early July. Mayflies accumulate around lights, making roads, streets, sidewalks, etc. slippery and dangerous. These annoying insects may fly into one’s face, ears, hair, land on clothing, crawl behind eyeglasses and splatter car windshields. Along lakeshores, piles of decaying bodies drift onto beaches and, if not removed, an offensive fish-like odor occurs discouraging tourists during the July 4th holidays. In addition, some people are hypersensitive, displaying symptoms of hay fever and asthma (allergies) from inhaling airborne pieces of their dead fragmented bodies.

Mayflies do not bite or sting nor feed on homes, furnishings, food, etc. (Their presence is an indicator of clean water and a healthy environment.) The chief importance lies in their value as food for fish, dragonfly nymphs, and birds. Anglers imitate the adults in dry flies, referred to as

“spinners” or “duns,” and pattern wet flies after the nymphs (Naiads).

MIDGES (Chironomidae)

Midges are the most wide spread and numerous insects resembling mosquitoes. Adult Midges are commonly observed flying in swarms or “clouds,” or are seen resting on fences, walls, under eaves and in protected areas such as porches and entryways. Individual adults will live about seven days depending upon the species and weather conditions. The larvae develop in sources having extensive areas of standing water.

Chironomid midges develop in moist soil, lakes, and slow moving rivers. The larvae scavenge decaying organic matter, feed on algae and other phytoplankton and the midges themselves can be an important part of the diet of fish. Although adults may emerge and be found during almost any time during the warmer seasons, emergences are often fairly synchronized, apparently being triggered by changes in weather patterns.

What attracts attention is the towering mating swarms that many midges produce. These form over some prominent point or conspicuous, usually light-colored object. This may include automobiles, a piece of lawn or porch furniture, or even a human. These mating swarms are made up almost entirely of the males. When the wing-beat frequency of approaching females is detected, a few will dart out to meet and mate with her. Because of the sensitivity of the swarming males to sound, you can often see erratic changes in the swarm pattern in response to sounds such as a handclap or even spoken word.

DIXID MIDGES (Dixidae)

Dixid Midges are common around moist areas where vegetation is abundant and may be seen

swarming at dusk along the edges of streams and lakes. The adults are short lived, usually being

active less than a week. The larvae are found in slow moving water, at the surface, and swim in

a characteristic “U” shape. These midges lack a proboscis and scales on the wings. Periodically,

dixids can produce staggeringly large emergences, but only in local and certain ecological

situations.

FUNGUS GNATS (Sciaridae)

Fungus Gnats are small (about ¼ inch long), black flies commonly found around decaying

vegetation. They have large wings and long antennae, but they are weak flyers and do not move

far from the breeding site.

Fungus gnats occasionally become a nuisance indoors when adults emerge in large numbers as

mosquito-like insects from potted plants or flower boxes containing damp soil rich in humus.

Adults are attracted to lights and are often first noticed at windows. In the household, fungus gnats are usually found around potted plants, because both the adult fly and the larvae require a humid environment. The larvae can complete their development by feeding on the wet and decaying organic matter in potting soil. The lifecycle may be completed in about 10 days, and the adults may live about 2 weeks.

DANCE FLIES (Empididae)

Dance Flies appear like mosquitoes by the way they swarm in sunlit areas in backyards and other

sheltered situations. The vertical movements of the swarming adults give them their common

name. Several of the Empis species are “balloon makers.” That is, the male flies capture an

insect and enclose it in a frothy bag that they carry as a lure to entice the female to mate. Some

species dispense with the froth, capturing and displaying live flies in front of females as a

preface to courtship. Others trick their intended with an empty ball of silk. Larvae are usually

found in rich, moist soil, decaying vegetable matter and in aquatic associations, or under the bark

of trees.

WOOD GNATS (Anisopodidae)

Wood Gnats are some of the better-known gnats, for they are attracted to light and can be found

near windows, especially in springtime. The adults can be found all year long, though. The

larvae live in rotting plants and rotting plant parts, fermenting sap, animal manure, tree trunks,

mud, and sometimes sewage. Adults are found on foliage in or near damp places, some are

found around flowing sap. They are sometimes seen in small swarms. Adults appear in two

variations: grayish black or reddish.