Mosquitoes-Control
More than 50 different kinds of mosquitoes have been identified in India All require water in their immature stages but the kind of water the female selects for her eggs varies considerably from one species to the next. The major pest species in coastal areas come from the artificial ponds created to cultivate frowns. At inland areas, many important pest mosquitoes develop in water pools formed in rainy season, percolation tanks, un-scientifically designed sewage and drainage systems.
Several important pest mosquitoes, however, breed around the home, and homeowners can substantially reduce mosquito nuisance caused by these species. This essay describes the habits of the most common mosquito pests that breed around the home and suggests methods to keep your village mosquito-free.
The Mosquito Life Cycle
All mosquitoes develop from eggs deposited by females that have previously fed on blood. The female mosquito is very specific about where she lays her eggs and searches diligently for water that will be suitable for her offspring. Most of the mosquitoes that breed around the home require stagnant water rich in decomposing organic material. This is not true of all mosquitoes; most pest species require clean, clear breeding habitats.
Having located a suitable water source, the female mosquito deposits the 100-200 eggs that will produce the next generation. Some species lay their eggs directly on the water's surface; others leave their eggs in an area that will flood at a later date. Mosquitoes are aquatic in their immature stages and, without exception, require water to complete their development.
Each egg that the female lays hatches into an aquatic organism that is termed a "mosquito larva." The larva stage is wingless, legless and wormlike in appearance. Mosquito larvae are very active and move almost continuously as they shuttle to the surface to obtain oxygen and dive to the bottom to find food. Larval mosquitoes feed on organic matter in the water and grow rapidly during this stage of their life. Within days, they enter a stage termed the "mosquito pupa" to allow formation of the legs, wings and other characteristics used in the adult stage. When this process is complete, the fully formed adult emerges from the pupal case. The entire life cycle from egg to adult can be completed in less than 10 days during periods of favorable temperatures.
Mosquitoes are expert fliers and many species can range great distances from their breeding sites. Flight, however, expends energy and most mosquito species have exceptionally high energy requirements. Mosquitoes obtain energy by feeding on flowers and convert the sugar from nectar as a source of fuel. Both male and female mosquitoes feed regularly on flowers but females require blood to produce fertile eggs. As a result, a female mosquito must find a host and blood feed before she can lay her eggs. Male mosquitoes do not lay eggs and, therefore, do not feed on blood.
Most of the mosquitoes that emerge in the wild never have contact with humans and obtain blood from the most common animals in their habitats. Some species prefer birds as blood meal hosts and rarely function as pests of humans. Others accept a wide range of animal hosts, including humans, and function as pests whenever they occur in numbers in areas frequented by humans. The mosquito species that breed around the home are considered "domestic species" and rarely range far from human habitations. All accept humans as a blood meal host, many will enter houses to feed and most are regarded as significant pests by the average homeowner.
Mosquitoes that Breed Around the Home
The Culex pipiens, is the most common mosquito found in urban and suburban areas. This mosquito will lay its eggs in virtually any receptacle containing water rich in decomposing organic material. Breeding habitats around the home include: discarded tires, unwashed bird baths, clogged rain gutters and plastic wading pools allowed to stagnate through disuse. The mosquito will not lay its eggs in any of these habitats if the water is too clear. Grass clippings, dead leaves and algae, however, quickly produce an infusion that is highly attractive to the female mosquito. Once the water begins to foul, The Culex pipiens mosquito will readily lay her eggs and will use any receptacle containing decaying organic material that is found on your property.
The eastern tree-hole mosquito, Aedes triseriatus, is another fairly common pest around the home. This mosquito lays its eggs in tree-holes that form in a variety of shade trees. Tree-holes are actually rot-outs in the tree-holes. They often form in a crevice where several branches meet or in an area where a branch has been lost The water that accumulates in tree-holes becomes exceedingly foul from the decomposition of wood accompanying the rotting process. The female eastern tree-hole mosquito is highly attracted to tree-hole water and glues her eggs just above the water line within the rot hole. The eggs hatch when rain raises the water level within this unique habitat. Discarded tires that trap decomposing leaves simulate the tree-hole habitat and are highly attractive to the eastern tree-hole mosquito as an egg-laying site. A single discarded tire in your yard can produce tens of thousands of tree-hole mosquitoes over the course of a season.
The white-dotted mosquito, Culex restuans, and the mottled wing Anopheles, Anopheles punctipennis, can also cause annoyance around the home. These species share habitat with both of the mosquitoes mentioned above and will enter your home to obtain a blood meal.
Based on surveillance and monitoring, we have to 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 essay provides basic information on larvicides, a type of pesticide used in mosquito control programs.
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 treatment of breeding habitats help reduce the adult mosquito population in nearby areas.
How are Larvicides Used in Mosquito Control?
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 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 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. 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. It is useful 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?
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.
Biological Control
The Gambusia, the fathead minnow, the freshwater killifish and two species of sunfish have become an important mosquito control alternatives to pesticides.
Gambusia are more effective in some situations than others. They generally work quite well in unused swimming pools, abandoned sewage lagoons, mine pits and permanently flooded stormwater facilities. Other larval habitats do not consistently provide a suitable site for Gambusia stocking but at times exhibit the proper characteristics that enable stocking to occur. These sites include freshwater swamps, ditches and woodland pools.
Gambusia use in an area is dependent upon sufficient water levels existing for the fish to survive and access any larval mosquitoes present. Although an eventual drydown may eliminate the fish from an area, the area should be considered for stocking if a few months larval control can be achieved.
The most important observation that was consistent throughout the study was that drydown was the primary cause of fish loss in an area. Low fish density was the reason many larval mosquito populations were insufficiently controlled by Gambusia. Anopheles spp. mosquitoes are particularly hard for mosquitofish to control when emergent vegetation provides them harborage.
chemical control:-
Methoprene:-
Methoprene is a compound 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
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.
Temephos:-
Temephos is an organophosphate (OP) pesticide 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 intertidal zones. It may be used along with other mosquito control measures. 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 overstimulate 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 inv ertebrates than alternative larvicides
Naled:-
Naled is an organophosphate (OP) insecticide. 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 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 also 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 overstimulate 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.
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. 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 which contain few non-target organisms.
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.
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.
The pupal stage is the briefest stage in the development of the mosquito. Although pupae are unaffected by organophosphate, pyrethroid, and other “nerve poison type” insecticides, B.t.i., and methoprene (AltosidŇ), there are some very effective pupicides. These agents will also control fourth instar larvae, which may be present when it is necessary to pupicide. As with larviciding, timely efforts to control concentrated populations of pupae can be of value in preventing the emergence of adult mosquitoes and reducing the need to adulticide. The following insecticides are recommended for the control of pupae of nuisance and vector species.
Bonide Mosquito Larvicide (98% Mineral Oil), per product label.
Golden Bear Oil 1111, per product label.
Adult control :-
A. Adulticiding with ground equipment
1. Thermal aerosols, fogging
Insecticide fogging can be an effective method in mosquito control. It is not meant to be used routinely but only when populations of adult mosquitoes reach public health or nuisance levels. These levels are highly variable and depend on the mosquito species involved as well as local environmental conditions. When fogging is deemed necessary, the following physical conditions should exist; these conditions are mostly encountered in the early evening hours or early morning.
1. Air temperature: 15°C or higher (60°F)
2. Light intensity: below 20 foot candles, with light meter
3. Wind velocity: 5-8 kph (3 to 5 mph)
4. Stable thermal conditions to allow fog to travel at ground level.
The only material recommended for fogging is malathion. The 95% malathion concentrate should be diluted as follows for fogging: 15 L (4 gal) concentrate is added to sufficient fuel oil to make 379 L (100 gal) final volume (0.4%). The diluted material is applied at a flow rate of 151 L/h (40 gal/h) with vehicle speed at 8 kph (5 mph). An experienced and knowledgeable operator and a properly equipped vehicle and fogger are absolutely essential.
2. Sprays by mist blowers and hydraulic sprayers
While mainly intended for use with residual insecticides, this equipment can be employed to apply dilute emulsions of the non-persistent insecticides malathion or pyrethroids to foliar surfaces for short-term residual mosquito control. The materials should be diluted and applied according to label recommendations for such equipment.
3. ULV (ultra low volume) spray applied by ground equipment
The technique of ULV has the advantage over fogging of being less dense and, therefore, less hazardous in urban traffic. Physical conditions as stated for fogging are generally desirable, and application should coincide with times of maximum mosquito adult activity in order to achieve maximum efficiency.
The technique of ULV employs more concentrated insecticides and the equipment for their application must be properly calibrated and serviced. Also, ground ULV applications do not always penetrate dense foliage as well as do fogging applications. Application of any ground ULV material should be performed under conditions also known to be best for efficient fogging operations (A1 above); wind speeds up to 16 kph (10 mph) are acceptable. Application should be made after sunset or before sunrise at temperatures of 15 to 28° C (60 to 82° F).
(a) Malathion (96-98%) at the flow rate of 90 mL/min at 16 kph or 45 mL/min at 8 kph (3 fl oz/min at 10 mph or 1.5 fl oz/min at 5 mph). With a constant volume flow meter and depending on conditions, e.g., acreage to be treated and period of mosquito activity, application may be made at 20 mph. According to the labeling of these products, their application by ground ULV is restricted to professional mosquito control personnel who have the experience, knowledge and equipment necessary to follow the technical instructions for their use.
(b) 5% pyrethroids - 25% piperonyl butoxide in recommended solvent at a flow rate of 118-133 mL/min at 16 kph (4-4.5 fl oz/min at 10 mph).
(c) resmethrin/piperonyl butoxide in a ratio of 1:3 such as SBP-1382/Piperonyl
Butoxide Insecticide Mosquito Fogger Formula II (18% and 54%, respectively). Mix 1.50 L (51 fl oz) of this product with 2.28 L (77 fl oz) refined soybean oil, light mineral oil, or other suitable solvent according to the label, and apply at a flow rate of 66.5 to 133 mL/min at 8 kph (2.25 to 4.5 fl oz/min at 5 mph) or 133 to 266 mL/min at 16 kph (4.5 to 9.0 fl oz/min at 10 mph). These rates are equivalent to 3.92 to 7.83 gm/ha (0.0035 to 0.007 lb/acre). Other formulations (e.g., ScourgeŇ 4+12) are available for use without dilution.
How to Reduce Mosquitoes around the Home?
Individual safety measures :-
Collected by
-----Tirumala Srinivas Reddy Dwarampudi, Rotary International District 3020