Town of Amherst NH

Mosquito Control

Town of Amherst
Public Health Division
Brian M. Gleason, Health Officer
175 Amherst St. – 673-7030

What exactly is a Mosquito Control Program? Mosquito control means different things to different people, and many misconceptions exist. Our control efforts are based on surveillance. We perform Integrated Mosquito Management, using targeted applications of very specific larvicides only after pre-determined thresholds of mosquitoes have been exceeded. Other areas of control are performed without the applications of pesticides at all.

Is Mosquito Control only done in the summer? Mosquito control is performed year-round. Mosquito larvae will usually hatch in late February, and by mid-March we are investigating wetland areas we have catalogued. This is called larviciding. This service will continue through the spring & summer into the fall, depending on weather and current mosquito surveillance.

What do you do in the winter? Believe it or not, mosquito control is performed during the winter months also. By cleaning ditches and catch basins, allowing the water to flow, we can discourage and eliminate mosquito breeding in areas, without the use of larvicides, and for extended periods of time.

How much “spraying” will you do in Amherst? This part of our program has the most misconceptions attached to it because most people associate the word “spraying”, with truck mounted units driving throughout neighborhoods emitting a cloud of chemicals. However in this case, mosquito spraying, specifically known as larviciding, is the application via a “backpack” style blower, of the naturally occurring bacterium found in soils called “Bti (Bacillus thuringiensis israelensis). Field Technicians will be dispatched to investigate certain areas in Amherst and if the pre-determined threshold of mosquitoe larvae is reached, a very specific, targeted application of Bti will result, but only in that area. Many factors influence this program – weather, current surveillance, topography, location, etc. Amherst does not perform routine, area-wide spraying for adult mosquitoes.

Is the application of “Bti” dangerous to me and my family? Bti poses very little threat to human health through either handling products directly or being exposed to them indirectly. To activate Bti toxins, alkaline conditions that exist only in certain insects’ (mosquito & black fly) digestive systems must be present. The acidic stomachs of humans and animals do not activate Bti toxins. There have been no documented cases involving toxicity or endocrine disruption potential to humans or other mammals over the many years of use in the US and around the world. The fact that Bti is a naturally occurring, widely distributed organism in the environment means that the average person would have multiple exposures to this bacterium throughout their lifetime, even if they never came in contact with a formulated product.

How do mosquitoes grow? Mosquitoes have a very interesting and unique biology. They go through 3 stages before maturity – egg, larvae and pupae. Each species has a different set of conditions required to complete this process. Some species lay eggs on damp soil, where they can remain for years before hatching. Another species needs emergent vegetation (such as the common cattail) to complete this process. Other species need saltwater to develop. One basic fact that is constant for all species – stagnant water is required for the maturation cycle. By removing, covering or draining containers, you can disrupt this process and reduce or eliminate mosquito annoyance and the potential for disease transmission from certain species in your own area. Wetlands and other mosquito habitats may need a professional mosquito control technician – please alert “Dragon Mosquito Control, Inc. office if you know of a potential mosquito habitat.

Why are there mosquitoes? Another common question and one that is more difficult to answer. While some species of insects and animals will eat mosquitoes in their different stages, no one species is totally dependent on mosquitoes to survive. All predators of mosquitoes are indiscriminate – they will choose other insects that are accessible, and usually prefer larger prey. Bats and purple martins are touted as great mosquito predators, and they can consume their fair share. But research has shown that mosquitoes comprise less than 1% of their total diet in the wild. Mosquitoes may play a role in the pollination of plants – both sexes, male and female, drink nectar for energy. Many species of flies are believed to be an important link in plant pollination – with the reduction of European honeybees due to parasites; flies have again emerged as the dominant species for pollination (the European honeybee is not native to this country, and before their introduction, flies and native bee species were the dominant pollinators). Mosquitoes are likely to play a small role in this as well.

Why do mosquitoes leave a bump after they bite? Only the female mosquito bites, to draw blood necessary for egg development. When a female mosquito pierces the skin with her proboscis (mouthparts), she injects a small amount of saliva into the wound before drawing blood. The saliva makes penetration easier and prevents the blood from clotting in the narrow channel of her food canal. The welts that appear after the mosquito leaves is not a reaction to the wound, but an allergic reaction to the saliva injected to prevent clotting. In most cases, the itching sensation and swellings subside within several hours. Some people are highly sensitive and symptoms persist for several days. Scratching the bites can result in infection if bacteria from the fingernails are introduced to the wounds

Can mosquitoes transmit AIDS? The HIV virus that produces AIDS in humans does not develop in mosquitoes. Disease transmission by mosquitoes is a very complicated process. If HIV infected blood is taken up by a mosquito the virus is treated like food and digested along with the blood meal. If the mosquito takes a partial blood meal from an HIV positive person and resumes feeding on a non-infected individual, insufficient particles are transferred to initiate a new infection. If a fully engorged mosquito with HIV positive blood is squashed on the skin, there would be insufficient transfer of virus to produce infection. The virus diseases that use insects as agents of transfer produce tremendously high levels of parasites in the blood. The levels of HIV that circulate in human blood are so low that HIV antibody is used as the primary diagnosis for infection.

How long do mosquitoes live? Mosquitoes are relatively fragile insects with an adult life span that lasts about 2 weeks on average, depending on species. The vast majority meets a violent end by serving as food for predators, or is killed by the effects of wind, rain or drought. The mosquito species that only have a single generation each year are longer lived and may persist in small numbers for as long as 2-3 months if environmental conditions are favorable. Mosquitoes that hibernate in the adult stage live for 6-8 months, but mostly in (hibernation).

Where do mosquitoes go in the winter? Mosquitoes, like all insects, are cold-blooded creatures. As a result, they are incapable of regulating body heat and their temperature is essentially the same as their surroundings. Mosquitoes function best at 80o F, become lethargic at 60o F and cannot function below 50o F. In tropical areas, mosquitoes are active year round. In temperate climates, adult mosquitoes of some species become inactive with the onset of cool weather and enter hibernation to live through the winter. Some kinds of mosquitoes have winter hardy eggs and hibernate as embryos in eggs laid by the last generation of females in late summer. The eggs are usually submerged under ice and hatch in spring when water temperatures rise. Other kinds of mosquitoes overwinter as adult females that mate in the fall, enter hibernation in animal burrows, hollow logs or basements and pass the winter in a state of torpor (these are the mosquitoes one might see on a warm January or February day). In spring, the females emerge from hibernation, blood feed and lay the eggs that produce the next generation of adults. A limited number of mosquitoes overwinter in the larval stage, often buried in the mud of freshwater swamps. When temperatures rise in spring, these mosquitoes begin feeding, complete their immature growth and eventually emerge as adults to continue their kind.

Why control mosquitoes at all? Mosquito control emerged at the beginning of this century once it was discovered that they can carry numerous viruses and bacterium, some fatal to man. Yellow Fever and Malaria were once endemic to this region, but are now either extremely rare or have been eliminated. Eastern Encephalitis, and now West Nile Virus, can also occur in New Hampshire, although more sporadically and without widespread human mortality. Mosquitoes have played an important role in the history of mankind – they have stopped wars, spread disease through entire populations, and altered human history in too many ways to count. It is estimated that mosquitoes have killed more human beings than all wars, famines and natural disasters combined – more humans than are alive today. 3-6 million people each year die from malaria alone, and up to 100 million are sickened annually. This is just from 1 disease transmitted by mosquitoes.

Do those new propane mosquito traps I see in the stores work?…..these devices will, indeed, trap and kill measurable numbers of mosquitoes. Whether this will produce a noticeable reduction in the mosquito population in your case will depend upon a number of factors, e.g. your tolerance level, absolute mosquito population size, proximity, size and type of breeding habitat producing re-infestation, wind velocity and direction, and species of mosquito present, among many other things. Depending upon their placement, wind direction, and trapping efficiency, traps may actually draw more mosquitoes into your area than they can possibly catch. Thus, the homeowner must still use repellents and practice source reduction methods as adjuncts to realize any measure of relief.

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