Gardening in the Washington DC Area Despite Mosquitoes

English ivy can harbor adult mosquitoes

I had originally wrote this article about mosquitoes in 2016 but the information is still relevant. Now is the time to stock up on fresh mosquito spray. I find it helps to have a new bottle every year. I am now using the towelettes for my face because even if I cover myself with clothes, the mosquitoes still get me in the face and neck.

If you are like me, you are plagued by mosquitoes in the garden. It is one thing to stay out of their way at dusk but it is quite another when the Asian Tiger attacks you all day long. In the spring of 2016, I contacted several companies to see if my property could be sprayed to prevent mosquitoes.  I don’t have a pond or pets but I have a lot of edible plants intermixed with other plants on the property.  I did not want the spray to harm the pollinators or the edibles (or my family!).  We have a lawn service that mows the grass but I never know when the crew is coming. Because I work in an office, I would not be home to let the pesticide applicator know where the edibles were nor would I be able to inform the lawn service crew when and if the place had just been sprayed with a pesticide. All of these factors made it complex for me to figure out how to control mosquitoes. At the same time, I attended a free presentation at a local library.  Kirsten Conrad Buhls, Extension Agent, Virginia Cooperative Extension, Arlington County, gave an excellent Powerpoint presentation entitled “Gardening in the Time of Zika: Nuisance Mosquito Management.”

Types of Mosquitoes

I learned that there are 40 mosquito species in Virginia in a variety of habitats but most are aquatic. Up until the mid-1980s, the most problematic species was Culex, which comes out at dusk and feeds at night. This species lives in the woods and prefers the type of stagnant water that usually does not occur near residential homes. However, they also breed in “container water.” Container water is fresh rain water that sits in pockets or depressions in objects or in containers.

After the mid-1980s, a Southeast Asian native arrived called the Asian Tiger mosquito, Aedes albopictus. The Asian Tiger is active during the day and prefers to breed in container water. The Asian Tiger has a cousin, Aedes aegypti, who also prefers to breed in container water. Both are vectors for transmitting diseases. Both can transmit the Zika virus but A. aegypti is more effective and considered a primary transmitter.  Both could prosper here, we have the appropriate environmental conditions, but currently there is not a substantial A. aegypti population.

Only females bite humans to get a “blood meal” before laying eggs. They are cold blooded so they don’t bite if the temperature is below 50 degrees. They can live as long as 2 to 3 months and adults that hibernate can live up to 8 months. This means that the problem is temporary; it exists only in the hot summer months.

Eliminating Container Water

Because mosquitoes breed in container water, anything that collects water should be dumped after it rains. Mosquitoes require as little as one tablespoon of water to lay eggs. It can take as short a time as 3 days for a new generation. After it rains, either dump the water or eliminate the object (e.g., put watering cans back inside the tool shed or throw away old tires). If the water cannot be dumped, such as a pond, make sure the pond has plenty of mosquito larvae eating fish, dragonfly larva, frogs, toads, and other such organisms. For rain barrels, use the mosquito dunks that are made of a safe bacteria. Or transform the water feature so that the water is moving by installing a bubbler or waterfall. Mosquitoes do not like moving water or moving air.

Kirsten dispelled common myths: Bug Zappers are not effective killers of mosquitoes, bats do not prefer to eat mosquitos, and purple martins are not big mosquito eaters. Plants that are reputed to repel mosquitoes do not work if they are just sitting in the landscape. A dense groundcover such as English ivy can harbor adult mosquitoes. It does not matter what you eat but mosquitoes are more attracted to big people and prefer men over women.

Protection and Sprays

If you are going to garden, wear long sleeves, long pants, socks, and shoes, or spray yourself with repellants such as DEET (25-30 percent), Picaridin (20 percent), oil of eucalyptus, or IR-3535 (Merck 3535), which is found in Avon’s Skin So Soft. Spraying Listerine and using dryer sheets, VapoRub, or vanilla are not effective protection.

The most environmentally friendly effective control is to control the larva stage. Spraying the adult mosquitoes in the landscape should be the last resort and should be based on surveillance data. The most popular mosquito adulticide for home landscapes is permethrin but it is toxic to fish, aquatic arthropods, and the non-target insects (pollinators).  Don’t be fooled when the pesticide applicators try to sell you on the fact that it is “natural” based on a chrysanthemum plant. What they are spraying is not natural, it is a chemical. There are substances called pyrethrins that are the active ingredients in pyrethrum, an extract of a flower, and these are are natural insecticides that act by blocking chemical signals at nerve junctions. However, commercial sprayers are not spraying pyrethrins. They are spraying permethrin, which is based on pyrethroids, synthetic pesticides. Permethrin is a pyrethroid insecticide that is light-stable and has a longer duration of activity against insects than pyrethrins. Thus, what the company is selling and spraying on your garden is permethrin, a chemical that will kill aquatic life and pollinators and render vegetables, herbs, and fruits non-edible.

Mosquitoes have a flying range of 600 feet, about 1 to 2 miles. If your property is sprayed, it will kill the existing ones but the next day more can fly in. If you spray your garden and your neighbors don’t, you can always inherit your neighbors’ mosquitoes. Commercial companies may tell you that the spray will last for a month but that does not prevent new mosquitoes from entering nor does the spray continue to kill for up to a month. In my mixed edible garden, only the grass could be sprayed which gets cut every few weeks. Since my grass gets cut by a service, I am concerned that the pesticide company will spray with a chemical one day and the lawn service crew will come and cut the grass the next day. I don’t know what harm that chemical would cause if the crew were to breath it in as they were cutting.

More Information and Resources

The presentation cleared up a lot of confusion and I decided not to have my garden sprayed. I am more vigilant about dumping water on my property. I try to garden in the cool morning with long sleeves and pants but sometimes I have to use the towelette on my face.  If you are faced with these same issue, learn more about mosquito management by calling the Arlington County Extension Office at (703) 228-6414 or visit the Master Gardeners of Northern Virginia website. The website has a tab with resources including the Powerpoint presentation. On Tuesday, June 19, 2018, there will be a presentation on identification and control of mosquitoes and ticks by the same group. This is free and registration is requested by contacting the Master Gardeners of Northern Virginia (call above number or visit website). This presentation will be at the Westover Branch Library, 1644, N. McKinley Road, Arlington, VA, from 7:00 pm to 8:30 pm.