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How gardeners can help control mosquitoes — and Zika

Bromeliad tanks form phytotelmata, a home to creatures including mosquitoes.
Bromeliad tanks form phytotelmata, a home to creatures including mosquitoes. Fairchild Tropical Botanic Garden

We’ve been hearing lots about the Zika virus the last few months. So what can we as gardeners and nature lovers do to avoid exposure?

Mosquitoes lay eggs almost anywhere there is standing water, with Aedes aegypti mosquitoes — the type responsible for transmitting Zika and other diseases — preferring stagnant water. Besides ensuring there is no standing water in empty flower pots, cups, garbage cans, birdbaths, folds in tarps over BBQs or in old tires, we should look at phytotelmata — bodies of water held by plants, or essentially a plant’s own water tank.

Bromeliad tanks serve as phytotelmata, but any cavity in a plant or tree can hold enough water for a mosquito nursery. A common practice is to hose out bromeliad tanks every few days to flush out any larvae or eggs. I even recently found mosquito larvae in a vase of water sitting on my desk, so they are not very choosy!

Look also in hollows at the bases of trees and at bases of leaves and palm fronds. If they hold water, hose them out every few days. Fallen plant debris may also provide spaces for water. Eggs may survive dry periods, so after rain it’s a good idea to hose out the bromeliads again to be sure.

Take a close look around your yard; you’d be surprised what items you may have left out that will hold water.

A common practice is to hose out bromeliad tanks every few days to flush out any larvae or eggs.

It’s important to eradicate eggs and larvae and not just adults, and there are various larvicides available. Fairchild is using VectoBac WDG, which uses Bacillus thuringiensis, a common soil bacterium, as a biocontrol. It is designed specifically for use against mosquito and black fly larvae.

Covering up also helps. The prospect of wearing long pants and long-sleeved shirts outdoors isn’t pleasant, but reducing exposed skin helps thwart mosquitoes. Don’t forget shoes, preferably ones that cover the ankle. Sandals and flip flops are tempting, but we all have gotten bitten on our feet before, so cover them. We can also avoid exposure by using window screens and not leaving doors open for any length of time.

If you plan to be outdoors much, avoid cologne and perfume. Mosquitoes are naturally drawn to carbon dioxide as well, so if you are exercising outdoors, you are producing more in the form of exhalations. Dressing in light-colored clothing is also recommended. And consider wearing gardening gloves to protect your hands while creating yet another barrier to mosquitoes.

At EPA.gov, you can find a list of mosquito repellants proven to work. Products containing DEET, picaridin (aka icaridin), oil of lemon eucalyptus, IR 3535 or catnip oil (Nepeta cataria) have been proven effective as mosquito repellants. Picaridin, unlike DEET, doesn’t dissolve plastics. Apply repellants over sunscreen if you are using both. If you spend lots of time outdoors, consider permethrin-treated clothing and camping supplies. The treated fabric repels insects even after washing. In all cases, follow the label instructions.

It’s anticipated that as cooler weather approaches, the threat should diminish. In the meantime, cover up, drain standing water, and get the facts at https://www.cdc.gov.

Kenneth Setzer is writer and editor at Fairchild Tropical Botanic Garden.

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