Since the introduction of the invasive Tiger mosquito (Aedes albopictus), most gardeners around the world face a similar struggle: whether or not practicing their hobby is worth a multitude of irritated and itchy bumps that can take days to heal.
An understandable reaction to this predicament is to use chemical sprays to rid yards of these pests. However, chemical pesticides are almost always extremely harmful to the environment, and can be harmful to us as well. Thankfully, there are organic solutions out there that are safe for our ecosystems, families, and wallets.
Beware the Tiger
Although most regions of the world have native mosquitos, they tend to be nocturnal, hunting only at night. The tiger mosquito, however, hunts during the day and can multiply rapidly, making it easily the most troublesome gardener pest. Also called the forest mosquito, the tiger mosquito originated in Southeast Asia and is distinct in it's large body with showy black and white stripes.
Since stowing away in the stagnant water filling tires on a shipping boat from Asia to Houston, Texas, in 1985, the tiger mosquito has spread to all 50 states. Although these mosquitos are native to tropical regions, they were able to adapt to temperate climates by hibernating over the winter. Not only are they prolific and active when we are, the tiger mosquito is a known vector for diseases such as dengue fever, yellow fever, malaria, and West Nile virus. They are also known to spread parasitic round worms that are harmful to cats and dogs. The Global Invasive Species Database lists Aedes albopictus as one of the 100 worst invasive species of all time.
What About DEET?
As someone whose yard was plagued by the tiger mosquito epidemic, I often found myself debating if I should douse myself in DEET before attempting to garden, or if I should simply let my beds be consumed by weeds. Insect repellent is almost always foul smelling and can dry and irritate the skin. Although there are no proven major health risks associated with DEET, the main ingredient of most insect repellents, there are many secondary concerns. The Centers for Disease Control recommends only applying repellent on clothes, never bare skin, as well as washing skin thoroughly after use. This would require gardeners to cover their skin completely while outside and to take a shower directly after they finish. It also says that most repellents are unsafe for use on children of three years or less. DEET can be dangerous if sprayed near the mouth or eyes, or inhaled in a room with poor ventilation. Some people even have allergies to DEET that can cause an irritating skin rash when exposed.
Other chemical sprays are sold to be applied to our lawn and landscape that are said to eliminate mosquitos. What the label doesn't include is the ensuing elimination of all other beneficial insects in our environment, such as lady bugs, bees, and praying mantis. Bee keepers commonly complain that their neighbor's spraying habits kill their bee colonies, even from houses away. The predatory insects that eat mosquitos and effectively control mosquito populations are being eradicated by sprays that claim to serve the same purpose. Pesticides are also very harmful to our watersheds. The chemicals that are absorbed by the ground collect in groundwater that runs into our streams, rivers, bays, and oceans, killing plants, fish, frogs, birds, and many other wildlife. Agricultural pesticide applications are one of the main contributors to the pollution of the Chesapeake Bay and subsequent destruction of the blue crab population there. These sprays are not permanent, usually needing frequent reapplication, especially after rainfall. Some complain that organic mosquito prevention is not as effective as pesticide application. However, many methods of organic prevention exist and when used in tandem with one another, you can be rid of these pesky blood-suckers at no risk to you or the environment.
Step 1- Get Rid of All Standing Water
The female tiger mosquito always lays her eggs near water. For this reason, surveying your lawn after a hard rain and noting danger spots can be invaluable. Birdbaths, plant saucers, and clogged rain gutters are common sites of water collection, so make sure you drain them after it rains. Indentations in your yard where rain water naturally collects should be filled in. Tiger mosquitos do not need the water source to be standing or stagnating water, so even a slow moving fountain or stream can be a source for mosquitos. Treat other standing water, such as rain barrels, with organic mosquito dunks. Dunks are floating rings that contain an organic larvicide BTI (Bacillus thuringiensis var. israelensis). The larvicide specifically attacks mosquito larvae, killing them before they can mature into adults. It will not harm other wildlife, people, or pets. One dunk treats a 100-foot area for 30 days.
Keep in mind that in suburban areas, our yards can be plagued by mosquitos even if we have no standing water. Our neighbors may, and the mosquitoes see no property lines. Talk to neighbors about their standing water issues. A free pack of mosquito dunks may convince them to toss a few in their ponds or fountains. If their mosquitos are bothering you, you can bet that they are getting bitten as well. Work together to solve the problem.
Step 2 – Encourage Natural Predators
Although the tiger mosquito does not have many predators, we can encourage the ones it does have.
Bats - Bats are one of the mosquito's most deadly beasts of prey. At night, bats come to life and flit through the air, using their sonar-like echolocation to hunt the tiny insects. Bat houses, like bird houses, offer bats a safe place to live. Setting one up in your yard will encourage these flying mammals to take up residence there and help control your mosquito population. Bat houses are wooden structures that look like plain boxes. There is a shallow opening on the bottom where the bats can enter. The small dark boxes imitate bat's natural dwellings, like small caves and hollow trees. Some insect eating bats can catch up to 600 bugs in only an hour! To dispel any myths and misgivings about bats, there are only three species which consume blood and they all live in Central and South America. Insect feeding bats have no interest in humans, and their swooping behavior is simply the dive they make to catch bugs, not to attack people. Bat houses can be easily constructed by hand (look at this handy site with step by step bat house instructions) or bought pre-made at a hardware or home store. Install your bat house high in a tree, on a tall pole, or directly onto the side of your house or other building. The box should be placed at least 15 to 20 feet off the ground and in a sunny spot. It usually takes up to one year for a bat colony to settle into a new bat box. Remember never to spray pesticides or other chemicals near your bat house. (On a side note, bat droppings, called guano, are an excellent nitrogen-rich fertilizer.)
Birds - Many birds are avid mosquito hunters. A few popular species include the chickadee, wren, and purple martin. Bird houses that are specialized for each species can be bought online, or built by hand. Plant brightly colored flowers near the bird houses, such as black eyed susan, and wait for a family to take up nest!
If you live near a lake or pond that is plagued by mosquitos, encourage the habitation of pond-living predators such as frogs, toads, damselflies, dragonflies, and larvae-eating fish. All of these water loving predators consume most small insects, including mosquitos.
Frogs - Frogs are most easily bought as tadpoles. Believe it or not, you can actually buy living tadpoles and use them to populate your water feature. Keep in mind that some of the tadpoles will not make it, so buy at least 10. There are many different species of frogs that are acclimated to a number of different climate conditions. Most of them eat mosquitos. Do some research on what type of frog will flourish in your area and will be able to survive the winter. Although it sounds easy to buy some pet store frogs and release them, many of these tropical frogs will not survive icy winters. Moreover, many are invasive species and you could find yourself overrun. Instead, catch tadpoles at a nearby pond during the late spring and early summer, or order a native species of tadpole online.
Insects - Conditions that will attract dragon and damselflies to your pond include plenty of underwater pond vegetation, a pond with varied depths (but at least two feet deep in some parts), and vegetation that surrounds the pond, like grasses and small shrubs. A few flat rocks near the water's edge allow for a warm spot for the insects to sun themselves. Planting bright flowers around the pond can attract native dragon and damselfly populations to move into your pond. If they don't come to you, head out to the nearest large pond you can find with a good aquarium net and go hunting for the dragonfly larvae, called nymphs. You'll have the best luck finding them between May and July. Wear some good rubber boots for slogging through the shallows and keep a sharp eye out for the aquatic nymphs, which look like brown water beetles, the size of a quarter. If there is a flourishing dragon or damselfly population in the pond, nymphs should be easy to find. After you catch some (about six will do) put them in an airtight container of water with some pond vegetation inside, and bring them home. As soon as possible, introduce them to your pond. You cannot buy dragonfly nymphs online due to the concern of releasing a potentially invasive species.
Fish - There are many types of fish that eat mosquito larvae. The most popular is the koi fish, known also for their beautiful scale colors and patterns. Koi are easy to care for and are hungry buggers, but grow to be quite large and need a large pond to accommodate their size. Mosquitofish (Gambusia affinis) is a fish known for its excellent larvae hunting skills. It was introduced as a control for mosquitos in many parts of the world, but turned out to do more harm than good due to it's invasive nature. But, in a closed pond, these small fish tend to be easier to care for than koi, and if they are restricted to one pond, they cannot affect the environment. The common goldfish is also an avid mosquito hunter and a great choice for smaller ponds. Again, do some research on what type of fish would flourish in your climate zone, since some types can be cold sensitive.
Supporting the predator populations in your environment is an easy and safe way to make a dent in your mosquito problem. Keep in mind that not all types of mosquito predators will live happily with one another. For example, large fish like koi and even large goldfish will happily snack on tadpoles, while large frogs such as bullfrogs will munch on any fish smaller than themselves. Likewise, both of these predators will chow down on dragon and damselflies and their nymphs. Do some research on which predator will do best for you and will be happiest in your pond before you decide which one to bring home.
Step 3 – Grow a Mosquito Garden
There are certain types of plants that are effective in repelling mosquitos. If planted, either en masse in one bed where the problem is worst, or scattered throughout the landscape, simple plantings can discourage mosquitos from lingering in your yard. These plants include citronella, scented geraniums, marigold, catnip, bee balm, and pitcher plants.
Citronella (Cymbopogon nardus), also called lemongrass, is a common ingredient in mosquito repelling products such as sprays and candles. The plant is a grassy looking shrub with a very strong smell that masks those scents that attract mosquitos. Native to India and Asia, this is the same herb used widely in Asian cuisine. Citronella prefers tropical climates, but makes a great annual from last to first frost. The clumping grass can grow to six feet tall, but as an annual usually peters out at around three feet. Planting citronella near vegetable gardens has the added benefit of ridding the garden of bugs with endeavors for your produce. The tall grass prefers full sun with a deep watering once a week during the growing season.
The scented geranium (Pelargonium) is a variety of the popular annual geranium. This geranium, however, has a fuzzy leaf that emits a burst of lemony scent when rubbed. Although the plant does not emit its smell as effectively as the citronella grass, it is a great temporary insect repellent. Simply pick a few leaves from your scented geranium and rub them on your skin for a quick and sweet smelling insect repellent. Although geraniums can grow to small shrubs in tropical climates, they will not tolerate a frost and are only hardy during the summer in most temperate zones. However, they make a great houseplant in a sunny window and many gardeners overwinter their geraniums inside. These plants make a great potted deck, porch, or patio plant and offer mosquito protection for those enjoying the weather on a balcony. Geraniums flourish in loamy soil, bright sun, and lots of water.
The common marigold (Tagetes) is a hardy annual with a scent that many insects find particularly offensive. They are often used as companion plants in vegetable gardens due to their effectiveness at warding off hungry insects. They are a tough plant and can tolerate many soil conditions, and even drought. In containers, or right in your garden bed, marigolds are easy to grow, colorful, and pack a beneficial scented punch. They grow best in lots of sun.
Catnip (Nepeta cataria), also called catmint, is a small and bushy herbaceous perennial, often grown to satisfy our feline friends. Besides inducing an interesting to behold euphoric state for our pet cats, the oil that catnip produces is also an effective mosquito repellent. Research suggests that a distilled form of the oil, nepetalactone, repels mosquitos ten times as effectively as DEET. In the garden, catnip is hardy and tough, with the added benefit of yearly protection due to the fact that it is a perennial. It is drought tolerant and can be grown in sun or part shade. It is also attractive, with silvery-green foliage and small clusters of purple flowers in the summer.
Bee balm (Monarda), also called horsemint, is a widely used and beautiful perennial with large combs of brightly colored blooms in mid-summer. Typically the herbaceous shrub is used to attract bees and butterflies, and many do not realize it's mosquito repelling properties. The foliage of the perennial gives of a strong incense-like odor that mosquitos cannot stand. It is also very easy to grow and does well in containers, garden beds, and most soil conditions as well as being highly drought tolerant. They can grow to two to three feet in both height and width, and make beautiful additions to either wildflower or formal garden beds.
The pitcher plant (Nepenthes or Sarracenia) is a carnivorous plant that actually consumes mosquitoes and other small insects for nutrition. In the Nepenthes genus, green or green and red pitchers hang from tendrils that extend from the plant's glossy leaves. The Sarracenia pitcher plants produce long tubular pitchers that stand tall and erect from the center of the plant. Large pitcher plants can trap and consume up to 100 insects per day. Insects are drawn into the pitcher structures because of their attractive scent and sometimes colorful pigmentation. Once inside, the insects find themselves trapped, either by downward pointing hairs or the mucus covered slippery sides of the pitchers. The fluid inside the pitcher contains a bacteria or an enzyme that kills and dissolves the insects, and the plant uses their remains as nutrition. Although there are a few hardy species of pitcher plant, most varieties cannot survive temperatures below 30 degrees Fahrenheit. Still, they make an excellent annual and houseplant, many owners choosing to place theirs outside during the summer and overwinter inside when it gets cold. Don't worry, the plants will go through a winter dormancy where they will not need insects, so you need not feed them when they come in. Keep in mind that these plants are very nutrient sensitive and can only be watered with distilled, rain, or well water. The minerals in normal tap water can be harmful to them. Also, never fertilize your pitcher plant. These plants make wonderful potted additions to porches and decks, controlling the mosquitos almost entirely within a 20 square foot area. Other carnivorous plants such as the venus fly trap, sundew, and butterwort, are also avid mosquito hunters but do not grow as large and therefore do not consume as many mosquitos as a large pitcher plant will. A grouping of these carnivorous plants, though, would be ideal. They all have very similar care, and in addition to needing distilled water, prefer a neutral potting medium such as sphagnum moss and frequent watering.
Step 4 – Stock Up on Organic Products
Organic products, such as the aforementioned mosquito dunks, are becoming more and more popular due to their effectiveness and safety. These include insect repellents as well as mosquito prevention sprays.
Many organic repellent sprays are available for purchase that use botanical scents that repel mosquitoes instead of chemicals. Lemon oil or eucalyptus sprays actually smell herbal instead of foul, and protect just as well. They will not irritate skin and can be used safely on children. Reapply every two hours for best results.
Homemade Repellant - If you really want to be sure you avoid any harmful chemicals, you can make your own natural mosquito repellent. You'll want to mix a repelling scented oil with either another oil or alcohol (since the scented oil will not mix with water). You can use:
- Cinnamon oil
- Lemon eucalyptus oil
- Citronella oil
- Castor oil
- Olive oil
- Sunflower oil
- Safflower oil
- Grape oil
Mix 10-25 drops of your scented oil to 2 tablespoons of your carrier oil and rub or spray the mixture onto your skin or clothes. If you want to make a large batch at once, use 10% scented oil in the mixture. Store in an airtight container in a cool spot. Reapply once every hour for best results.
There are also yard sprays that repel mosquitos from your landscape and are not chemical based. The most popular of these is a garlic spray called Garlic Barrier, the main ingredient of which is a strong garlic extract. To use, mix the extract with water and a small amount of sticking agent such as oil or dishwashing detergent. Spray your landscape thoroughly and reapply every two weeks, or after rainfall. The smell is not noticeable to humans, and will not bother other insects, wildlife, or pets.
The infestation of the tiger mosquito has made it almost unbearable for many gardeners and outdoor enthusiasts to even venture outside without unpleasant consequences. But, as chemical applications continue to harm our environment, we need to remember that the easy way out is not always the best. Organic mosquito prevention techniques are a safe way to repel these annoying pests, and offer lasting solutions that work for you year after year. Try a few of these easy solutions and see how well they can work together.