There is an ongoing battle in our yards and gardens. The leader of the resistance is a vamp with a taste for blood. But there are some practices gardeners can use to reduce the number of hungry female mosquitoes lurking out there.
Besides ruining a day in the yard, certain mosquitoes can transmit West Nile and other diseases in their quest for the blood needed to produce eggs. In fall, mosquitoes mate and the males die. The females spend the cold months hidden in protected places, such as hollow logs and in the cracks of buildings. So it is a good practice to clean up debris and caulk buildings in fall.
We all know that female mosquitoes need still water to lay eggs. Effectively minimizing standing water by improving natural drainage is the key to controlling mosquitoes. The addition of solar pumps to water features also helps. The circulating water produces rippling, which drowns the pupae. By increasing water flow and decreasing water surface tension, it is also more difficult for the females to lay eggs.
Permanent sources of water that contain fish such as ponds, water gardens, and canals usually develop ecosystems that can support a larger, more diverse concentration of natural predators. The Journal of the American Mosquito Control Association states that, under normal circumstances, natural predators eat 95 percent of an adult mosquito’s offspring.
Stephen Tvedten, author of Natural Mosquito Control, (who holds pest control certifications in several states and is head of the Advisory Board for the Natural Pest Control Council) found that using potentially hazardous synthetic pesticides is not the best way to control mosquitoes. In fact their use often creates an abnormal situation by also killing large numbers of natural predators (which are slower to repopulate). When the remaining mosquito larvae hatch in a few days, their numbers steadily increase unchallenged.
Some Basic Practices to Control Mosquitoes
• Install tight screening and weather stripping.
• Use sodium vapor lamps or yellow non-attractant light bulbs outside.
• Empty all standing water and clean roof gutters.
• Keep tall grass and weeds trimmed to allow airflow through the yard.
• Rather than spraying synthetic poisons in breeding areas, using strains of Bacillus thuringiensis (Bt) such as Bt israeliensis (BTI), or Bacillus sphaericus (Bs) will kill the mosquito larvae by interfering with their ability to digest food. Bt is available in floating discs or as granules.
• As a last resort, add lightweight mineral oil to standing water where fish or dragonflies are NOT present.
When working in the garden or just enjoying the outdoors, try some of the many natural repellents on the market. Garlic, cedar, peppermint, lemon oil, or citrus-based sprays are good mosquito repellants, as are herbal essential oils including basil, citronella, eucalyptus, lavender, and lemongrass. Soybean oil-based repellent protects from mosquito bites for 1½ hours. Since mosquitoes are not strong flyers, you can also set up a fan barrier to blow them away from you before they have a chance to bite.
While deet is an effective insect repellent, its potential side effects include memory loss, headache, weakness, fatigue, muscle and joint pain, tremors, and shortness of breath in humans (especially children). Until further studies are done it should be used with caution. A personal non-deet mosquito deterrent that I have found effective is a clip-on battery operated fan using metofluthrin cartridges. It is safe if used as directed.
Mechanical mosquito traps with bait will kill thousands of mosquitoes in your yard, but they can be expensive to purchase and maintain.
Mosquito Traps and Baits
A homemade bait trap containing spinosad, an approved organic substance made with soil bacterium or boric acid, mixed with fermented fruit juice will attract and kill adult mosquitoes. Both are considered safe for humans and other mammals, but be sure to place your bait traps out of the reach of children.
Mechanical mosquito traps – such as Mosquito Magnet – utilize scent-bait, carbon dioxide generation, plus fans and suction to attract, trap, and kill mosquitoes in a 1-acre area. This is a rather pricey solution, but I can testify that it does work.
Biocontrol Methods and Natural Predators
Predatory fish such as mosquitofish (Gambusia affinis), millionfish (Poecilia reticulata), minnows, and certain species of carp – such as goldfish and tilapia – will eat mosquito larvae in stand-alone garden ponds.
Motionless ponds without fish can be treated with Bacillus thuringiensis israelensis (an organic bacteria that kills mosquito larvae). Another way to disrupt the breeding cycle is to dust areas where mosquitoes breed with food-grade diatomaceous earth.
Encourage damselflies, dragonflies, and other natural predators such as bats, lizards, frogs, spiders, and native birds including chimney swifts. This free pest control squad will chow down on thousands of mosquitoes without your having to lift a finger.
A version of this article appeared in a June 2016 print edition of State-by-State Gardening.
Photography courtesy of Yvonne Bordelon.