Summer Harvests – Rainfall and Mosquitoes

According to the Farmer’s Almanac (and AccuWeather), summer will be a rainy one. This could be good for gardens and other outdoor projects requiring water.

The impact of Metro DC water utility company WSSC’s July 1 rate increase could be lessened by making use of all the free falling water. I started to write about the effective use of rain barrels, rain gardens, and other rain harvesting strategies but switched gears to address prevention of a most unwanted summer harvest – mosquitoes.

With rain comes puddles and pools where they shouldn’t be. Standing water – even an ounce – makes the perfect nursery for mosquitos, a summer visitor that has in recent years become more than a nuisance.

This summer, attention is on the Zika virus although so far the 820 cases of Zika reported in the US are imports – travelers returning home, their sexual contacts, and babies infected before birth.

The Food and Drug Administration and related agencies are ramping up to address the possibility of transmission of the virus when at some point local mosquitoes will feed on infected travelers and begin spreading the virus to non-travelers.

They are also considering other ways infection can take place, such as through blood transfusions. State and local government agencies are rolling out information to raise awareness, not cause alarm. Forewarned…

The two likeliest mosquitoes to carry Zika in the Mid-Atlantic also transmit its cousins – chikungunya, dengue, and West Nile.

Aedes aegypti mosquito

Aedes aegypti, also known as the yellow fever mosquito, is active year-round and at any time of day. The female is actually attracted to fatty acids associated with bacteria that break down leaves and other organics in water. (source:

Aedes albopictus mosquito

Aedes albopictus, aka Asian tiger mosquito, is active just after dawn and just before dusk. Females are aggressive biters Although not being very efficient at transmitting disease, it can do infect humans with over 30 diseases to humans. (source:

Eggs can hatch after a dormant period so it’s important to watch out for damp areas inside your home and out. Being weak flyers, Aedes bite close to where they hatch. For that reason too, a fan makes a useful tool for keeping them at bay.


Like Zika, these viruses have been reported in the Mid-Atlantic but are imported by travelers returning from the Americas, Africa, or Asia.

  • Chikungunya is a virus where fever and joint pain are the most common symptoms. A person could also experience headache, muscle pain, joint swelling or rash. As of January 2016, all cases of the virus in the US were found in travelers to affected areas of the world. There is no vaccine and treatment consists of symptom management.
  • Dengue fever symptoms are high fever, headache, vomiting, muscle and joint pain, and skin rash. It can develop into hemorrhagic fever or shock syndrome which are more serious, possibly fatal, conditions that cause bleeding and low blood pressure.
  • West Nile can go undetected in 70 to 80 percent of those who become infected. Fever, headache, body aches, skin rash, and swollen lymph nodes are symptoms most likely to be experienced. In a minority, stiff neck, sleepiness, disorientation, coma, tremors, convulsions, and paralysis can occur.


  • West Nile can be transmitted to horses.
  • Dogs and cats are susceptible to heartworm disease.
  • DEET should never be used. Only use repellants specifically for animals to prevent adverse reactions.

To minimize the likelihood of being bitten

  • Cover arms and legs
  • Use mosquito repellant. Be aware of how often the repellant should be re-applied.
  • Avoid standing water – whether in a garden, around a rain barrel, or on a patio. Indoors, be alert to areas that can hold dampness since the yellow fever mosquito likes being indoors too.

Mid-Atlantic Mosquito Resources

Delaware District of Columbia Maryland New Jersey Pennsylvania Virginia West Virginia

Strategies to discourage the growth of mosquitoes

  • Dispose of any container – tire, bucket, pot – that can collect water.
  • Fill in hollow stumps or tree rot holes.
  • Drill a hole in the bottom of a tire used as a swing to allow water to escape.
  • Refresh water each week in birdbaths, watering troughs, plant trays, and non-aerated ponds.
  • Store wheelbarrows upside down.
  • Add fish (goldfish, minnows, gambusia [mosquito fish]) to your pond or fountain (or rain barrel). They love noshing on mosquito larvae.
  • Be sure that recycling containers have holes at the bottom to allow water to escape.
  • Eliminate areas on your property where standing water can occur. This may require grading, filling in land or planting cattails, an extraordinary plant with a wide variety of uses from converting marsh to dry land, diaper padding, fuel and food.
  • Report any county- or state-owned land where standing water is observed. Talk to neighbors, report theirs too, if necessary.
  • Ensure water can freely flow through catch basins, storm drains, and uncovered gutters.
  • Frequently inspect outdoor faucets and sprinklers for leaks, fix promptly.
  • Place Bti (Bacillus thuringiensis var. israelensis) – a bacterium that is harmless to fish, birds and mammals – in standing water. These are sold as pellets or doughnut-shaped rounds.

DEET and DEET Alternatives

Because of reports of severe, even fatal, reactions and reports of toxicity in fish, many people are resistant to using DEET (diethyltoluamide), the CDC top-recommended repellant. It is the most common active ingredient in products designed to repel a variety of insects including mosquitoes, ticks, and leeches.

Various agencies emphasize correct usage of DEET products (apply to exposed skin and clothing, wash off during periods it isn’t needed) to avoid complications such as skin irritation, difficulty breathing, burning eyes, headaches and seizures.

DEET is also a solvent, meaning it can dissolve plastic, rayon, nylon, and other synthetic fabrics as well as varnishes.

Alternatives to DEET

  • American beautyberry (Callicarpa), a shrub in the mint family, has four chemicals which have been found to repel insects. The USDA Agriculture Research Service has actually patented one, callicarpenal. The other chemicals are borneol, intermedeol, and spathulenol.
  • Citronella candles are summer standards found in every type of store. Citronella is the essential oil found in lemongrass, the stalky plant that flavors Thai foods so well. It has been found to be an effective repellant of Asian tiger mosquitoes, leeches, and stable flies. It has been known to increase the heart rate of some people when applied directly to the skin.
  • Icaridin (hydroxyethyl isobutyl piperidine carboxylate) has been found to be more effective than DEET for repelling certain insects. Also known as picaridin or KBR 3023, Consumer Reports ranked a 20% concentration of the chemical as a top repellant. It is sold as Bayrepel and Saltidin.
  • Oil of lemon eucalyptus or OLE, is a product of the lemon eucalyptus tree. A natural aging process of the leaves is replicated in the lab, producing a refined oil known as PMD which is known as Citriodiol.
  • Permethrin is a synthetic chemical used to treat a number of conditions and is used by the U.S. military as a defense against ticks and mosquitoes, applied to uniforms and supplies such as tents. Toxic to fish and cats, permethrin is on the World Health Organization’s List of Essential Medicines (the most important medications needed in a basic health system). It is generally applied to mosquito nets and clothing and is also found in flea collars.
  • SS220 is a synthetic chemical that has proven to be “significantly better” than DEET at repelling sand flies and mosquitoes. And unlike DEET, it does not cause allergic skin reactions, lasts longer on the skin than other repellents, does not have an oily consistency, and does not tend to plasticize. Its greatest drawback seems to be that it is more expensive to manufacture than DEET or other repellants.

Scents That Mosquitoes Hate

  • Basil, lime or sacred is traditionally held to be an effective repellant among a host of other beneficial uses.
  • Rose-scented monarda is said to attract butterflies and bees but repel mosquitoes.

More plants, along with several recipes for skin and other applications, can be found at Auntie Dogma’s Garden Spot. The leaves of these plants must be bruised or crushed to release the oils that produce the scent that drive the mosquitoes away. One easy way to do this is to scatter them on the ground and walk on them. Other strategies are to burn them or make a solution for spraying or applying to skin.

Marigold is that rare plant that has such an objectionable scent just by growing that it repels mosquitoes (and not a few humans). It also protects tomato plants from insects. Unfortunately, its bright leaves attract wasps so you’ll have to find a balance between insects for this to work for you.

A lab in Brazil found coffee to be a useful weapon against mosquitoes. “Day-old caffeine solutions took 20 days to kill 100% of mosquito larvae; 25-day old caffeine solutions killed 100% of mosquito larvae in 1 day.”

Conspicuous by its absence from the list is the mosquito plant. Although labeled as citronella, it is actually a type of geranium that is marketed in the U.S. and Canada as Pelargonium citrosum or Citrosa geranium. But according to a 1996 study published in the Journal of the American Mosquito Control Association, 1) ‘Pelargonium citrosum’ is not a valid taxonomic designation and 2) research has shown it to be ineffective: “Not only was the plant ineffective at protecting humans against Aedes mosquito bites, the mosquitoes were seen landing and resting on the citrosa plant on a regular basis.”

In summary then, summer’s abundance of rain offers opps for lots of free water for your home and gardening needs. Zika is a concern for those who travel to high-infection areas; those planning to attend the summer games in Rio would do well to take heed of travel advisories. West Nile Virus and Eastern equine encephalitis virus (EEEV) are more immediate concerns for residents of the Mid-Atlantic, courtesy of mosquitoes.

The best strategy for preventing mosquito-borne disease is to avoid getting bitten. Make your yard and home a mosquito-free nursery and enjoy the summer rain.


Avoid Mosquito Bites. Centers for Disease Control and Prevention. June 7, 2016.

Chikungunya Virus. U. S. Centers for Disease Control and Prevention.

DEET. Wikipedia. June 2016

Dengue Fever. Wikipedia.

Grow Safe, Natural Mosquito Repellants. Sandbeck E. Mother Earth News. June 2012. This article also provides a recipe for an effective DEET-free repellent spray.

Mosquito Repellents That Best Protect Against Zika. Consumer Reports. April 2016.

Mother Nature Wins Again. Beautyberry and the deet. Vasdani K. Updated July 2008.

West Nile Virus. Symptoms. U. S. Centers for Disease Control and Prevention.

Zika – What Can Be Done. U. S. Centers for Disease Control and Prevention. [PDF]


Roxanne Corbin has lived most of her life in the mid-Atlantic. She is a latent artist and wistful-thinking gardener. An information hunter by trade, Roxanne is currently working to transition from the corporate world to managing a research and writing business of her own.

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