Dragonflies may be your answer to natural mosquito control
You may not be aware, but Aug. 20 is World Mosquito Day. It isn’t a day to celebrate mosquitoes. Instead, it marks the discovery, made in 1897 by the British doctor Sir Ronald Ross, that female Anopheles mosquitoes transmit malaria to humans. Mosquitoes are the deadliest of all the insects, ticks, and small animals that can spread disease.
So how can you best protect yourself and your family, with a little help from the winged world?
First, a little background.
The mosquitoes that spread the Zika virus also vector Dengue, chikungunya, and yellow fever. The primary mosquito that spreads these diseases is Aedes aegypti, and to a lesser degree, A. albopictus.
The life cycle of mosquitoes can go full cycle, from an egg to an adult, in as little as 10 days during the warm months. These mosquitoes are daytime flyers and breed in small collections of fresh water. Possible breeding sites include birdbaths, animal water dishes, tires, paint buckets, plant trays, empty garbage cans, lids, wheelbarrows, non-native bromeliads, vases, etc.
If you have bromeliads in your landscape, both Aedes species of mosquitoes will breed in non-native bromeliads, especially the Neoregelia. If you are getting bitten by mosquitoes during the day, you can either reduce the number of bromeliads in your landscape or use Mosquito Bits, which are effective in killing mosquito larvae. The label states that the bits can be applied every 7 – 14 days, but it recommends reapplying every seven days during the hotter months.
Simple steps to protect yourself from mosquitoes
To protect yourself and your family, the first thing to do is to survey your yard for standing water. The more thoroughly you check every area of your yard, the better. If any containers have collected water, empty them, and either remove them from the landscape, turn them upside down, or lean them against something so they can’t collect water.
Wearing insect repellent can also serve as a primary prevention method. The CDC provides a list of mosquito repellents such as oil of lemon eucalyptus, picaridin, etc. The entire list can be found at this website: https://www.cdc.gov/mosquitoes/prevention/index.html.
Research has also been done on the efficacy of plant essential oils in repelling insects.
Many research studies have been published in the Asian Pacific Journal of Tropical Diseases showing that plant essential oil effectively repels Aedes aegypti. One such study looked at Peppermint oil and found it provides remarkable repellent properties against adult A. aegypti. Peppermint oil provides 100% protection for 2.5 hours, and from 2.5 to 3 hours, only one to two bites were recorded. Another study examined clove essential oil mixed with coconut oil, which repelled Aedes aegypti for 96 minutes.
Enter dragonflies, exit mosquitoes
Dragonflies are also called pond or mosquito hawks, so why not invite them to your yard?
They are unmatched as fliers and have an agile flight pattern. The diet of dragonflies mainly consists of insects such as mosquitoes, black flies, horse flies, deer flies, and small gnats. Most dragonfly species hunt during the day, when the Aedes mosquitoes are active.
Dragonflies are commonly found around freshwater because they feed on mosquitoes and their larvae. Hopefully, you already see dragonflies in your yard, and if you do, you can help them by simply placing tall sticks (i.e., bamboo, metal, etc.) throughout your landscape beds to give them a resting perch.
If you want to keep dragonflies in your yard, consider building a pond filled with plants. This will provide the dragonflies with a place to lay their eggs and a habitat for their aquatic larvae, called naiads, to find food. To help protect the naiads, don’t keep your pond too clean. Some leaves at the bottom of the pond will provide them with places to hide from predators. The plants in the pond will be used by the dragonfly, which lays her eggs on the leaves, and the naiads during their incomplete metamorphosis.
When the time comes, the naiads will climb out of the pond, either onto the bank or a nearby plant, where they molt into an adult. Just as butterflies do, once they emerge from their chrysalis, the dragonfly needs to pump up their wings and allow their body to harden before they can fly. It can take a dragonfly several days to harden completely before taking flight.
How to create a dragonfly pond
Those looking for a worthy project should consider creating a dragonfly pond! Important characteristics of a pond to support dragonflies include water persistence, plus the amount and structure of the aquatic vegetation present. A large diversity of aquatic vegetation is vital for a good dragonfly pond.
Less important are the surface area and age of the pond. In addition, vegetation planted around the pond is important for providing nighttime roosting, hunting, and other benefits for the adult dragonflies. If you are interested in learning more, check out this manual, titled Backyard Ponds: Guidelines for Creating & Managing Habitat for Dragonflies & Damselflies.
Though mosquitoes can bother us throughout the day, there is no need to give up gardening. Adopting many of the recommendations listed above will allow you to continue to enjoy the outdoors while minimizing potential mosquito bites. If you want a new project, consider creating a dragonfly pond and start planning today!
Sally Scalera is an urban horticulture agent and master gardener coordinator for the University of Florida’s Institute of Food and Agriculture Science.