Keep mosquitoes away!

People have been battling mosquitoes for a very long time and with good reason.


Mosquito bites are no fun. They itch like crazy, no matter how much you scratch (which you shouldn’t). Worse than that, mosquitoes carry diseases that can make you very, very sick, or even kill you.

Female mosquito feeding (Global Panorama) CC BY-SA 2.0

Diseases carried by mosquitoes

Malaria and dengue fever certainly come to mind when you think of mosquito borne diseases, but they aren’t the only ones carried and transmitted by mosquitoes. Each year, nearly 700 million people around the world become infected with mosquito borne diseases and more than one million of those people die. In the US, over 3,000 people a year die from mosquito borne diseases, such as Zika and West Nile, as well as malaria, dengue, yellow fever, chikungunya, and St. Louis encephalitis.


I had never heard of the last two before, so I had to look them up. Chikungunya [chicken-goon-ya] showed up in the Americas in 2013. It causes joint pain, headache, and fever. If you get St. Louis encephalitis, you might feel nothing, or you may experience fever, headache, nausea, tiredness, and vomiting. In both cases, you might die. COVID-19 is not believed to be carried by mosquitoes, but canine heartworm is.


Different species of mosquito tend to carry different diseases, but I can’t tell them apart. I do know that if I get bitten, it’s by a female mosquito.


Mosquito feeding

Male and female mosquitoes both eat nectar, but female mosquitoes need blood for their eggs. They get that blood from mammals, from us. When a female mosquito lands on you, she drools numbing, anti-coagulating spit on your arm before inserting her mouthparts. That’s why you often don’t feel the bite until it’s too late. And that saliva can contain deadly viruses. What’s a gardener to do?


Interrupting the mosquito cycle

Mosquitoes need standing water in which to lay their eggs. Unfortunately for us, mosquitoes can lay those eggs in as little as one tablespoon of water. That handful of water might be found in rain gutters, planter saucers, old tire swings, or a trowel that was left behind in the yard. Eliminating all of those potential egg-laying locations goes a long way toward reducing mosquitoes in the garden.


What about ponds, fountains, rain barrels, birdbaths, and pet water bowls?


These water sources can also be used by mosquitoes for egg-laying, but adding one simple  ingredient eliminates the problem: mosquito dunks.

Mosquito dunks are made out of a dried bacterium that mosquito larva love to eat. The bacteria kills the mosquito larva, but it is safe for people, pets, livestock, wildlife and plants. This bacteria, Bacillus thuringiensis ssp. israelensis, also called Bti, is also toxic to some moths, flies and beetles. Mosquito dunks are approved for organic use. A single mosquito dunk lasts for 30 days and can treat 100 square feet of water. Each donut-shaped dunk can be broken into smaller pieces, depending on the area being treated. The same bacterium is also available as granules that can be sprinkled on soil infested with fungus gnats. You may also be able to contact your local Vector Control office for free mosquitofish.

Mosquito dunks prevent disease (Kate Russell)

Plants that [supposedly] deter mosquitoes

You may have heard that there are plants you can add to your landscape to deter these pests. The lists and descriptions certainly are enticing and convincing. Sadly, research has not held up those claims in the field. It’s one thing to smear yourself with a concentrated mix of essential oils in a laboratory (assuming you aren’t allergic). It’s something else entirely to stand 30’ away from a patch of citronella grass or a rosemary shrub and expect significant results.


Will these plants deter mosquitoes? Probably not enough to make a difference. But maybe, if you plant enough of them, and you rub your hands through them every once in a while as you enjoy your garden, it might help. If nothing else, these plants look and smell lovely in a landscape, and many of them are edible:

• allium family - garlic, onions, shallots
• basil - delicious tender annual
• bee balm - gorgeous flowers loved by honey bees and other pollinators
• catnip - invasive mint with purple flowers that may lure local cats
• citronella - an attractive ornamental grass for warm regions
• lavender - drought-resistant, low-maintenance, and the honey bees love it
• marigolds - attractive, self-seeding annual
• mint - delicious, nutritious, and invasive!
• rosemary - delicious and drought-resistant
• sage - delicious and drought-resistant
• scented geraniums - lemony fresh scent; grows best in warm regions

Sorry for bursting any bubbles out there. I think that these plants do provide some help, just not as much as many sources claim. The only exception I could find was oil from the lemon eucalyptus (Eucalyptus citriodora syn. Corymbia citriodora) plant, but few of us are able or willing to grow this 60-foot tall Australian herb in our yards.


To safely repel mosquitoes while outside, the CDC recommends using EPA-approved repellents that contain at least one of these active ingredients: DEET, picaridin (known as KBR 3023 and icaridin outside the US), IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone. They also suggest applying permethrin to clothing.


And get rid of any standing water.