4 easy ways to protect your garden from cicadas
Trees and bushes, beware.
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This year, the ominously named Brood X cicadas are expected to erupt from their 17-year snooze and swarm the eastern United States—just when all your trees, flowers, seedlings, and lawn are in the middle of their critical spring growth.
And because cicadas eat sap and lay their eggs in trees and other shrubbery, they can wreak havoc on your yard. Here’s what you need to do to protect your plants.
First, what are cicadas?
Cicadas are insects that look like large flies with big heads. There are more than 3,000 species of cicadas, but the bugs that make the headlines are periodical cicadas, who take an all-or-nothing approach to life. Instead of developing some sneaky way to avoid predators, cicadas’s life strategy is to overwhelm their environment with so many cicadas at a time that some of them have to be able to reproduce.
Most familiar insects hatch, eat, mate, and die in a single season. Periodical cicadas hatch, suck sap from grasses for nourishment, then dig their way underground to subsist on food from plant roots.
Then, years later, cicadas start stirring when the soil temperature reaches 65°F. Suddenly, all at once, the slumbering bugs dig their way out of the soil, molt, and emerge with new wings and a powerful urge to mate. They swarm on trees, piercing bark to suck sap from branches and twigs and making an incredible racket as every male cicada simultaneously buzzes for a mate. Four to six weeks later, the noise dies down as the adults mate, lay their eggs, and die.
Bushes and young trees are most at risk
Periodical cicadas are fussy about their food. They don’t bite humans or animals, and the adults only drink sap from plants with woody stems and branches—the same places they lay their eggs.
The problem with cicadas is that they do attack young woody plants of all sorts, more than 270 different types are at risk. Sapling trees, ornamental shrubs, blueberries, grape vines, and bramble fruits like raspberries and blackberries are all in danger, as are oaks, maples, cherries, dogwoods, and redbuds.
Newly planted trees and woody plants with stems up to one half-inch in diameter are especially vulnerable to damage from cicadas, which suck out sap and cut slits in tree branches to lay clutches of eggs.
Making those slits, known as flagging, won’t hurt mature trees, which can regrow damaged branches. Unfortunately, young saplings up to four years old may be killed or stunted as females deposit up to 600 eggs in clutches of 25 at a time.
Gardens and lawns should be spared
Although cicada swarming over your tomato vines and marigolds may be annoying, they won’t harm your garden flowers or vegetables.
Cicadas also leave lawns alone. You may find cicada emergence holes about a half-inch wide in your lawn, with mud “chimneys” up to 3 inches high. Those holes are annoying, but they won’t permanently damage your lawn, and may provide helpful aeration.
The one upside to cicadas? All those rotting adult bugs act as nitrogen-rich fertilizer. Scientists have found that while oaks grow less than normal during the year that cicadas emerge (and suck sap out of trees), they grow more than average the four years after a swarm.
Ways to keep your most vulnerable plants safe from cicadas
1. Delay any new planting
Prevention is the most effective approach to keeping young trees safe from cicadas. If you live in a Brood X area, think seriously about delaying planting trees until 2022.
2. Put up physical barriers
If you already have young trees and bushes in the ground, your best bet is to put up a physical barrier between the cicadas and your plants. Cicadas prefer to lay their eggs in slits in branches with about a half-inch diameter, so your job is to protect those branches.
Wrap your trees, bushes and shrubs in netting with holes 1 cm or smaller to keep cicadas off your plants. You can use fine mesh insect netting or barrier plant bags for individual trees or shrubs. Avoid “bird netting,” which usually has net openings too large to keep cicadas out.
Make sure you tie the bottom of the bag or netting tightly against the bottom of the trunk so that cicadas can’t crawl up under the netting. Take the netting down when cicada season is down to allow better air circulation.
- Get Agfabric insect screen and garden netting at The Home Depot for $19.98
- Get Brave Tour nylon netting mesh with drawstring at Amazon for $15.59
3. Skip chemicals
Avoid chemical insecticides for cicadas. For one thing, chemical insecticides aren’t as effective as netting. In one study, trees that were treated with common insecticides suffered eight to 25 times as much damage as trees covered with mesh netting.
Insecticides also need to be applied every two to three days for the four to six weeks adult cicadas are around, as new cicadas will come to your trees from nearby areas. That’s a lot of insecticide, which may kill bees and other beneficial insects, as well as injure people, pets, and birds that either come in contact with the insecticide or eat dead or dying cicadas.
4. Take extra care to water and mulch
If your trees and woody plants do suffer cicada damage, you can help revive them. Make sure your plants get the equivalent of 1 inch of water a week, and consider applying mulch around the tree or plant—without touching the trunk—to help water in the soil and help keep the soil temperature moderate.
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