With the recent spread of the Zika virus and its link to microcephaly, proper mosquito control is something that people want and need to understand more than ever. The Aedes mosquito can carry Zika. Some types of mosquitoes can also transmit malaria, West Nile virus, dengue fever, yellow fever, and other diseases in various regions of the world.
Climate change is almost certainly contributing to the increase in some tropical diseases such as Zika, due to higher temperatures and more precipitation in many areas, in the tropics and beyond. [Source: The Guardian]
Unfortunately, conventional tactics for killing mosquitoes are not always effective, and they tend to be toxic. Zika can harm the development of fetuses and can harm some adults; meanwhile, exposure to toxic insecticides can harm everyone (including fetuses). It doesn’t make sense for society to accept that we should have to suffer from the long-term effects of slow poisoning (and chronic and fatal illnesses) from insecticides and pesticides when less-toxic, effective alternatives exist. We cannot just “fog” the whole world in a cloud of insecticides to try to avoid Zika. Furthermore, the use of insecticides often backfires and has unintended consequences, such as killing other insects and animals that eat mosquitoes.
“Aerial and ground applications of pesticides have long been used for mosquito control, but many believe that these methods fail to sufficiently control mosquito populations, [and that they] promote resistance and kill other species that would have acted as a natural predator to mosquitoes.
Dino Martins, PhD, a Kenyan entomologist, in an interview with The Guardian said that while pesticides can reduce the population of flying adult mosquitoes that transmit the virus, they will fail to deal with the epidemic that threatens to become a global pandemic, and warns that spraying landscapes is extremely dangerous. ‘It is a quick fix but you pay for it. You kill other species that would have predated on the mosquitoes. You also create a mosaic of sprayed and unsprayed low densities of chemicals that fosters the rapid evolution of resistance.’
Already there is emerging resistance to insecticides among Anopheles mosquitoes. Additionally it is impossible to fumigate every corner of habitat where mosquitoes might breed.
According to Dr. Martins, the explosion of mosquitoes in urban areas, which is driving the Zika crisis, is caused by a lack of natural diversity that would otherwise keep mosquito populations under control, and the proliferation of waste and lack of disposal in some areas which provide artificial habitat for breeding mosquitoes.
The efficacy of adulticidal pesticide applications (aerial or ground spraying) has been called into question over the years. Further, the drifting spray impacts other non-target organisms like pollinators, birds, fish and amphibians. Commonly used mosquito pesticides like permethrin, resmethrin, naled and malathion are all associated with some measure of human and ecological health risks, especially among people with compromised immune systems, chemically sensitized people, pregnant women, and children with respiratory problems, such as asthma.
…Individuals can take action by eliminating standing water, introducing mosquito-eating fish, encouraging predators, such as bats, birds, dragonflies and frogs, and using least-toxic larvacides like bacillus thuringiensis israelensis (Bt). Through education of proper cultural controls, and least-toxic and cost effective biological alternatives, the use of hazardous control methods, such as toxic pesticides, can be eliminated.
- Clean-Up–Eliminate pooled or stagnant waters from debris, containers, drains, and anywhere that pools water. Watch out for [and fix] leaky faucets. Mosquitoes can breed in puddles the size of dimes, so keep a keen eye out for stagnant water!
- Natural Predators– Use indigenous fish populations, like bluegills or minnows, to eat mosquito larvae in shallow waters and ornamental pools. Copepod crustaceans can also be used to eat mosquito larvae in ditches, pools and other areas of stagnant water. Don’t forget about bats either! One bat can consume 1,200 mosquitoes in an hour, and many bats are in trouble from a disease wiping out their population. Help conserve these important mammals while keeping the mosquito population down by installing a bat house!
- Behavior Modification–Wear long sleeves and long pants/skirts, and use least-toxic mosquito repellent when outdoors. Try to avoid being outside at dusk when mosquitoes are most active.
- Attentive Monitoring– Check sources of water for signs of mosquito larvae often.
- Least-toxic Pesticide Options– Use Bacillus thuringiensis israelensis (Bt), a biological larvicide (“mosquito dunk”) that prevents mosquitoes from developing into breeding, biting adults in standing waters that cannot be drained.
- Take Action–Let your local council members, mayor, or state delegates know that safer, more sustainable options exist. [Click here and scroll to the bottom of the article to] download our sample letter to send to public health officials in your area.
Beyond Pesticides’ Mosquito Management program page has a list of resources that can help you and your community safely manage mosquitoes, including least-toxic mosquito repellents, bed nets, and proper clothing that can be used to keep mosquitoes safely at bay.”
In addition to the behavior suggestions mentioned above, these are some other useful suggestions for keeping mosquitoes (and other bugs) away:
- Make sure any windows that get opened have window screens, and repair/tape any tears in the screens.
- Turn a fan on. Mosquitoes avoid strong wind.
- Remove all standing water from your yard. Don’t let excess water sit in plant pot dishes. Clear out debris from gutters. Remove water from birdbaths, any discarded tires, unused water troughs, etc. If you use rain barrels, make sure they have screens and that the screens are on tightly. If you have a compost pile, make sure it has drainage, is not soggy, is covered with a thick layer of leaves or grass clippings, and is not located right next to your living quarters.
- Cover up with loose, light-colored clothing. Wear shoes and socks instead of sandals. Change and wash your socks and clothing regularly, as mosquitoes are attracted to stinky feet and sweat.
- Use mosquito netting over baby carriers, strollers, beds, etc.
- Avoid drinking beer or eating/drinking dairy products when in a mosquito-prone environment. They seem to be attracted to beer and possibly also to lactic acid.
- Methods and products that don’t really work or don’t work well include: 1.) Ultrasonic devices. 2) Vitamin B patches. 2.) Repellent candles (e.g., citronella candles): They don’t work nearly as well as clothing or skin treatments, and 3) Bug zappers: They may attract more mosquitoes and other bugs to the area, and can kill beneficial bugs.
Studies are finding that mosquito repellents that use oil of lemon-eucalyptus (with some PMD) are just about as effective as DEET, and they last longer. The EcoSmart organic insect repellent (which uses a variety of other botanical ingredients) was also found to work well, but it needs to be reapplied frequently (every 2-3 hours). Picaridin (or icaridin, or KBR 3020) is a less-toxic synthetic repellent than DEET and it works almost as well. [Sources: NPR and EWG]
Avoid using permethrin-based repellents, even those used to treat clothing and not applied to skin. Also avoid products with more than 30% DEET. And don’t use “foggers.” Those are all very toxic. Also, don’t use any aerosol sprays (use lotions or pumps instead). Don’t use repellents on babies under 6 months, and don’t use lemon-eucaluptus/PMD on children under 3 years old. [Source: EWG’s Guide to Bug Repellents in the Age of Zika: Top Choices, and Do’s and Don’ts for Avoiding Bug Bites]
Other than lemon-eucalyptus oil, most botanical/plant-based repellents have not been found to be as effective as DEET or Picaridin-based repellents (especially for repelling the types of mosquitoes that can carry Zika). However, you could still experiment with rubbing a few of these bug-repelling plants on your skin or clothes (try a small area first, to make sure it doesn’t cause an allergic reaction). Better yet, planting some of these herbs and plants in your yard could help reduce the mosquitoes (and also fleas and ticks) in the area around your house. (Always be sure to buy organic—or non-treated—plants or seeds, so that they don’t kill off pollinators and other beneficial bugs and creatures.) Turning your yard into a thriving garden will also help create more much-needed habitat for beneficial bugs, birds, and other species that help keep the mosquito population under control.
- Bayberry (shrub)
- Geranium (especially citronella geranium)
- Lemon eucalyptus
- Sweet woodruff
- Thyme (especially lemon thyme)
[Sources: Book: Naturally Bug-Free: 75 Nontoxic Recipes for Repelling Mosquitoes, Ticks, Fleas, Ants, Moths & Other Pesky Insects, by Stephanie Tourles, Storey Publishing, 2016; and “Repel Mosquitos with These Plants,” by Julie Fryer, Mother Earth News]
A company is currently working on developing Kite Patch and Kite Shield, technologies intended to prevent mosquitoes from detecting the CO2 that we emit, to make us virtually invisible to mosquitoes. Time will tell whether these technologies are effective. If they are, they are likely to become quite popular.
Resources and references:
EWG’s Guide to Bug Repellents in the Age of Zika (including tip sheets that you can print out), from Environmental Working Group
How to Repel Mosquitoes Safely, Beyond Pesticides
Mosquito Management and Insect-Borne Diseases, Beyond Pesticides
Book: Naturally Bug-Free: 75 Nontoxic Recipes for Repelling Mosquitoes, Ticks, Fleas, Ants, Moths & Other Pesky Insects, by Stephanie Tourles, Storey Publishing, 2016
“Repel Mosquitoes with These Plants,” Mother Earth News
“Mosquito Deterrents: The Good, The Bad, and the Potentially Effective,” Smithsonian Magazine