What’s the purpose of mosquitoes?

Interesting question. You’ve probably asked yourself that a hundred times while swatting one.

Turns out this is actually a debatable subject. There are supporters for their total eradication and those who think they are an important, irreplaceable part of the ecological systems of the planet. For further reading on this topic, see Nature’s A World Without Mosquitoes [1] or NPR’s Three Nice Things We Can Say About Mosquitoes. [2]

It’s interesting that as good as humans are at driving so many species to extinction, we haven’t even made a dent in this one. But the fact is, they are here, in your yard and you’d like for them not to be there, or at least not bother you. The following information might help.

A few mosquito facts

• only the females bite [2]
• the mosquito life cycle from egg to adult is one week (or less) [5]
• mosquitoes can breed in less than an ounce of water [8]
• mosquitoes are pollinators
• over 3,500 species of mosquito exist worldwide of which only 200 bother humans [1]
• there are only 63 species in Georgia [6]
• mosquitoes can find you from as far away as 35 meters (~ 100 feet) [4]
• most mosquito species are crepuscular (dawn or dusk) feeders [3], however…
• the Asian tiger mosquito, will fly and feed during the daytime [3]

What can you do about mosquitoes?

An ounce of prevention

Here are some things you can do to keep them from breeding:

Allow no standing water

They can’t handle moving water and prefer water that is shallow.

• clean out eaves and gutters
• remove vegetation or obstructions in drainage ditches that prevent the flow of water
• replace water in birdbaths twice a week
• add a bubbler to birdbaths to create moving water
• replace water in pet and other animal feeding dishes or container at least twice a week
• change water in bottom of plant containers, including hanging plants, at least twice a week
• fix dripping outdoor faucets that create pools of water

(most of the above list from UGA: Controlling Mosquitoes Around Our Homes and Neighborhoods [20])

Your ground cover could be a breeding ground

Since mosquitoes need just a few drops of standing water to breed, the large leaves of some ground covers create perfect little pools of water after a rain. English Ivy is especially bad, and has other issues as well.

Pay attention to rain barrels

Saving water in a rain barrel is a very good thing. But remember that it’s standing water and a good breeding ground for mosquitoes if you don’t use it frequently. [10]

• always use a mosquito-proof screen to seal and cover the rain barrel.
• keep the water you save free of leaves and other organic material
• remove the water that pools at the top of the rain barrel at least twice a week
• clean the barrel on a regular basis

Some things that work

Attract Dragonflies

One dragonfly can eat up to hundreds of mosquitoes per day. [11]  If you can put a small pond with moving water in your back yard, you will attract dragonflies and these will help reduce the mosquito population. The larvae are also voracious predators, eating most living things that are smaller than they are. [12]

We’ve had a small pond in our back yard for several years now, and it seems that the mosquito population has been reduced significantly.

Use outdoor Fans

This is easy and very effective.  It you are entertaining outside and want to keep the mosquitoes away, aim a box fan or an oscillating fan at your party. Turns out that mosquitoes are poor fliers. They fly at about 1.5 miles per hour while the air from a fan is moving at about 15 miles an hour.

We had heard about this, but recently read an article in the New York Times which is worth a minute of your time. Best part is there are no chemicals on you or in the air and it works. [17]

Choose your clothing

Wear protective clothing, long pants, long-sleeve shirts, shoes and socks. Mosquitoes are less attracted to light clothing than dark. Remember, mosquitoes can bite through T-shirts and other lightweight, tight-fitting clothing. [20]

Also, several companies are now selling insect repellent clothing which is treated with permethrin, the only pesticide approved by the EPA for pre-treated fabrics. This keeps you from putting repellent, such as DEET, directly on your skin. The claims are that it also works for ticks. We haven’t done any homework on this clothing, but you might want to check it out. Most manufacturers claim you can wash up to 70 times without re-treatment.

DEET

DEET was developed in 1944 by the United States Department of Agriculture for use by the United States Army following its experience of jungle warfare during World War II. It was originally tested as a pesticide on farm fields, and entered military use in 1946 and civilian use in 1957. It was used in Vietnam and Southeast Asia. [18]

There are alternatives to DEET, but if it doesn’t cause issues for you, DEET still seems to be the most effective. Read the EPA’s information sheet on DEET and use this product with care.

Mostly myths and urban legends

Citronella

You like citronella and have always used it.  But how effective is it really?

If you don’t mind the odor, citronella is a mosquito repellent. Citronella oil is one of the essential oils obtained from the leaves and stems of different species of lemongrass. Citronella oil is also a plant-based insect repellent and has been registered for this use in the United States since 1948. [21]

But burning citronella oils or candles have limited effectiveness. First, they only have a range of 3 – 5 feet, so you have to sit close. Second, a study by the U.S. National Library of Medicine showed that “… the overall reduction in bites provided by the citronella candles and incense was only 42.3 and 24.2%, respectively.” [22]

Attract Bats

It’s a myth that bats eat lots of mosquitoes. While they do eat mosquitoes, they are opportunistic and their diet consists of many other flying insects. Mosquitoes have comprised less than 1% of gut contents of wild caught bats in all studies to date. [13]

Attracting bats has lots of benefits but don’t think that they will solve your mosquito problem.

Attract Purple Martins

This also is a myth. It was started by an amateur ornithologist who determined that Purple Martins must eat their weight in insects every day in order to survive. He never intended to mean all of those insects were mosquitoes. Individuals hoping for a silver bullet to mosquito control seized on this comment and started promoting Purple Martins. [14]

The facts are a little different. First, during daylight, purple martins often feed voraciously upon dragonflies, known predators of mosquitoes. Second, at night, when mosquitoes are most active, purple martins tend to feed at treetop level, well above most mosquito flight paths. [14]

Ornithologist James Hill, founder of the Purple Martin Conservation Association (PMCA), writes, “The number of mosquitoes that martins eat is extremely insignificant, and they certainly don’t control them. In-depth studies have shown that mosquitoes comprise no more than 0 to 3 percent of the diet of martins”. [14]

Really bad ideas

Bug Zappers

We think these things do way more harm than good.

Bug zappers do indeed kill some mosquitoes. However, the only two controlled studies conducted to date by independent investigators at the University of Notre Dame showed that mosquitoes comprised merely 4.1% and 6.4% respectively of the daily catch over an entire season. Even more important was the finding in both studies that there was no significant difference in the number of mosquitoes found in yards with or without bug zappers. [15]

What is particularly disconcerting, however, is the number of non-pest insects that comprise the vast majority of trap catch.  Many of these insects are beneficial predators on other insect pests.  They in turn constitute a major part of the diet of many songbirds. [15]

Misting systems

These are pesticide dispensers and the worst idea yet. Please don’t consider one of these systems / services, and if you have one, please consider discontinuing its use. No matter what the vendor tells you about its safety to humans and pets or use of only organic insecticides, pesticides used this way are indiscriminate killers and harmful to wildlife.

The following information is from the EPA: [25]

• Since pyrethrins and permethrin are toxic to all insects, they may kill beneficial insects such as honeybees, ladybugs, butterflies and other non-target species. In addition, permethrin is very highly toxic to fish.
• Outdoor residential misting systems have not yet been studied sufficiently to document their effectiveness in controlling mosquitoes or other yard and garden pests, nor have they been scientifically proven to control or prevent the spread of West Nile Virus or other diseases.

It’s also worth your while to read:

• American Mosquito Control Association: Position on Misting Systems
• Environmental Protection Agency: Mosquito Misting Systems

You’ll be helping wildlife and saving yourself some money.

Georgia Mosquitoes

What Mosquitoes are in Georgia?

There are 63 species of mosquito in Georgia. Of these, only 10 or 12 are pests to people. Some species of Georgia mosquitoes can breed in salt water. [20]

If you’re interested in more detailed information on Georgia mosquitoes including ID guides and distribution maps, check out the Georgia Mosquito Control Association’s website.

What diseases might these Mosquitoes carry?

There are several viruses transmitted by mosquitoes that can cause encephalitis (inflammation of the brain) which fortunately, is rare in Georgia. The four most common types of encephalitis here are the West Nile virus, LaCrosse, Eastern Equine  (EEE) and St. Louis. Like encephalitis, yellow fever, dengue, and malaria were once common diseases in Georgia. However, they have long been eradicated. The mosquitoes that carried these diseases are still present, but in the absence of the disease agent, the primary discomfort now is the bite itself. [20].

The three that have been most in the news lately are:

• West Nile
• Zika
• Chikungunya

The Zika virus

This is a tough, fast moving subject.  As of the date of this writing, which is September 12, 2016, the CDC reports that there have been 75 cases in Georgia, but none that were acquired locally.  [26]  This, of course, could and most likely will change.

Initially the thinking was that the Zika virus only had adverse affects for pregnant women.  The picture on this may be changing as well as this report from Bloomberg explains. [27]

References and Additional Information

[1] Nature: A World Without Mosquitoes
[2] NPR: Three Nice Things We Can Say About Mosquitoes
[3] Wikipedia: Mosquito
[4] American Mosquito Control Association: FAQ
[5] CDC: Mosquito Life Cycle
[6] UGA: Experts warn to keep up guard against mosquitoes in final month of season
[7] UGA: Mosquito Control
[8] University of California – Green Blog: Mosquito management for ponds, fountains and water gardens
[9] Maryland Department of Agriculture: Avoid Asian Tiger Mosquitoes
[10] The Sacramento Bee: How do you stop mosquitoes from invading rain barrels?
[11] Smithsonian: Fun Facts About Dragonflies
[12] Wikipedia: Dragonfly
[13] American Mosquito Control Association: FAQ – Bats
[14] American Mosquito Control Association: FAQ – Purple Martins
[15] American Mosquito Control Association: FAQ- Bug Zappers
[16] American Mosquito Control Association: Position on Misting Systems
[17] The New York Times: A Low-tech Mosquito Deterrent
[18] Wikipedia: DEET
[19] EPA: DEET
[20] UGA: Controlling Mosquitoes Around Our Homes and Neighborhoods
[21] Wikipedia: Citronella Oil
[22] U.S. National Library of Medicine: Evaluation of the efficacy of 3% citronella candles and 5% citronella incense for protection against field populations of Aedes mosquitoes.
[23] Georgia Mosquito Control Association: About
[24] Georgia Mosquito Control Association: Mosquito Information
[25] EPA: Mosquito Misting Systems
[26] CDC: [Zika] Case Counts in the U.S.
[27] Bloomberg: Zika May Cause Brain Damage in Adults Too