Dealing with Mosquitoes in the Garden

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 fact, we have 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.

No doubt you have seen plants that are supposed to repel mosquitoes but in reality they do not work if they are just sitting in the landscape. The best you can do is spray yourself and your clothing. If you intend to spend time working in the garden, wear long sleeves, long pants, socks, and shoes, and 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.

You have also seen companies selling mosquito spraying for your property. 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” because it comes from 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 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 spraying on your garden is permethrin, a chemical that kills aquatic life and pollinators and render vegetables, herbs, and fruits non-edible. This is especially important if you have your edibles mixed in with your ornamentals and you are relying on pollinators to set fruit.

In addition, 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.The most environmentally friendly effective control is to control the larva stage. 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.

Don’t get your landscape sprayed. Be vigilant about dumping water after it rains. Garden in the cool morning with long sleeves and pants. Don’t spray your face with mosquito spray but spray the back of your hand (before you put your gardening gloves on) and then apply the back of your hand to your neck, tips of your ears, temples. If you have any more useful suggestions, please enter them in the comments. But don’t let the mosquitoes deter you from gardening!