Mosquitoes and Spraying
We work hard to encourage pollinators in our yards, but what do we do when it comes to mosquitoes? Mosquitoes can make time in our yards unpleasant, and can sometimes spread disease. However, spraying for mosquitoes damages the environment and can be self-defeating by killing their predators and by creating genetic resistance over time, making stronger and more toxic chemicals necessary. Fogging/barrier sprays can drift well beyond where they are sprayed and kill all insects in the spray radius.
Many insects are important pollinators, and killing them indiscriminately affects the health of the entire ecosystem. When beneficial insects and spiders are killed, it also means less food for birds to raise their young. Spiders are especially important for the development of young birds, and many are predators of mosquitoes as well. A decrease in food supply is thought to be a major contributor to the decline in bird populations.
Misleading or incomplete information from companies that spray can also be a problem. Companies sometimes tout their products as “natural” or “safe”, and it can be hard to find out which chemicals are actually being used and in what quantity. “Natural” or “organic” pesticides, such as pyrethrins, can be just as deadly for non-target insects like bees and butterflies. Many pesticides last longer than stated, and can also wash into waterways.
Safer, More Effective Solutions
Luckily, there are better ways to reduce the chances of being bitten. They basically fall into two categories: minimizing contact and reducing the mosquito population.
Public health specialists recommend several basic measures one can take to minimize exposure to mosquitoes:
· Minimize exposed skin by wearing long pants and long-sleeved shirts.
· Use an effective repellent like DEET.
· Avoid the hours from dusk to dawn, when mosquitoes are most active.
· Use a fan to create a breeze where people are seated; mosquitoes are notoriously weak flyers and can’t cope with even light wind.
A complementary approach is to use environmentally sound ways to minimize the mosquito population in your yard. Although most pesticide applications target adult mosquitoes, it is much more effective, safer and cheaper to target their early immature or “larval” stage.
Female mosquitoes search out still, stagnant water and can lay eggs in as little as a bottlecap of water, laying up to 100 eggs at a time. The eggs hatch in only a few days, with a full cycle from egg to adult of approximately 8-10 days.
The most effective step you can take to deal with mosquitoes is to remove any standing water in your yard. Examples of places that you might not think of that can hold standing water are:
● Plant saucers or empty flower pots
● Plastic toys or any molded plastic that has small areas where water can collect
● Gutters - be sure to keep them clean and ensure they drain completely
● Corrugated downspout extenders - try replacing with smooth pipe or cover the outlet with screening
● Trash and recycling bins - lids, handles or empty bins can trap water
● Tarps
● Watering cans
● Wheelbarrows
● Old tires
Bird baths are another place that can often attract egg laying females. If possible, change the water in the bath every few days to prevent any larvae from developing. If that isn’t possible, you can add a water pump or “water wiggler” to keep water in motion. Mosquitoes will avoid moving water for laying their eggs.
Another strategy is to use what is called Bti (short for Bacillus thuringiensis israelensis), a bacterial “larvicide” which specifically targets mosquito physiology during their larval stage. Female mosquitoes can lay up to 500 eggs in their short lives, and it is a much more effective and targeted strategy to prevent their eggs and larvae from developing into biting adults. Bti has no effect on most insects, but is lethal to the larval stage of certain fly species.
Bti is widely available commercially as small donut-like “dunks” that can be purchased at most hardware stores. Bti can be used to create a “bucket of doom” trap in your yard. Doug Tallamy and Homegrown National Park have details on how to create one. The bucket acts as the perfect habitat to lure females to lay their eggs, and the small amount of Bti added to the bucket then prevents any larvae from maturing.
Encouraging a diversity of insects, birds and bats with native plantings also helps to increase the mosquito predators in your yard. Working to remove invasive plants that alter the ecosystem and provide habitat for mosquitoes is also important. For example, English Ivy’s dense growth covers puddles and soggy soil, and provides a cool, damp spot for the mosquitoes to shelter on a dry, hot day. It can also often hide trash that may hold enough water for mosquitoes to breed. Additionally, a research study has shown that the type of mosquitoes that carry West Nile Virus receive a boost in development from the leaf detritus of invasive Amur Honeysuckle and Autumn Olive.
Because mosquitoes are highly mobile, flying insects, it can be hard to control them by only concentrating on your own yard. A neighborhood or community-wide approach may be more effective. Read about how neighbors in D.C. worked together to reduce mosquitoes through education and teamwork.
Links for further reading/viewing:
-Our joint Cary Library/LLL presentation by Aaron Anderson of the Xerces Society or his more recent presentation for the Mass. Pollinator Network
-The Xerces Society’s top 5 reasons not to spray for mosquitoes at home
-Information from Homegrown National Park and Wild Ones about mosquito buckets
-The Xerces Society’s infographic for smart mosquito management at home and their Guide to PFAS Pesticides: Simple Steps To Protect People and Pollinators