Cicadas—How to Protect Your Yard During Bug Attack

Hillary Mayell
for National Geographic News
April 19, 2004
The emergence of the Brood X cicadas has gardeners in more than a dozen
U.S. states wringing their hands, and worrying about what to do.

Nursery attendants, entomologists, and horticulturists seem united in their advice: Unless you own a nursery or a fruit orchard, there's nothing to worry about.

"What we're telling people is, honestly, there is no big cicada scare. It's not going to do a lot of damage," said Beth Abbundi, a spokesperson for Behnke Nursery in Beltsville, Maryland. "Cicadas won't hurt your garden at all; they don't feed on vegetables and flowers. It's the egg-laying that causes the damage, and only to very young trees. On older, healthy trees, they won't cause any damage."

Mitch Baker, a horticulturist and vice president of American Plant Food, a Washington, D.C.-area nursery, concurs, albeit a bit more cautiously.

"We're in something of an epicenter, and millions and millions [of cicadas] will be emerging here," he said. "The cicadas are not a threat, but you will see evident and obvious damage to younger trees as well as older ones. It can be somewhat disfiguring, but it doesn't threaten the overall health of the trees."

"What we're trying to tell people is that this should be viewed as a natural phenomenon, not something we should fear or get all excited about. It's nature's way of pruning."

The cicadas should begin emerging in early to mid-May after spending 17 years underground as nymphs sucking on tree roots. Once they reach the surface, they quickly morph into winged creatures and spend the entire four weeks of their above-ground lives flying from tree to tree in search of a mate, mating, and then dying.

A female cicada's dream home for laying her eggs is the new growth on a branch of a hardwood or fruit tree.

"The female uses her ovipositor to dig a channel in a branch, where she leaves her eggs—that's what causes the damage," said Mike Schauff, a research entomologist with the U.S. Department of Agriculture's Agricultural Research Service.

A female bent on egg-laying could make anywhere from 5 to 20 slits in a branch before moving on to another one. Twigs or branches the diameter of a pencil or thinner are most often damaged. Around late June, the tips of tree branches will start to droop or flag.

Apple, pear, dogwood, oak, and hickory are favorite hosts, according to the Agriculture Extension Service of the University of Tennessee, but many others have been reported.

"They're not really that interested in pines or any of the evergreens, azaleas, hollies, laurels, and other ornamentals," Schauff said.

Net the Young Trees

The Brood X cicada population is one of the more far-flung populations. Gardeners in regions of Maryland, southern Pennsylvania, northern Virginia, New Jersey, Delaware, small parts of West Virginia, North Carolina and northern Georgia, southern Indiana, Kentucky, Tennessee, Ohio, and Illinois can expect to be inundated.

The sheer volume of the emergence can be staggering.

"Southwest Ohio can expect five billion, and that's probably a lowball estimate," said Gene Kritsky, a biologist and cicada expert at the College of Mount St. Joseph in Cincinnati, Ohio. "Seventeen years ago we estimated that there were 50 to 100 per square yard [0.8 square meter] in parts of Cincinnati."

With each female laying up to 400 eggs, homeowners in these regions with young trees might consider netting them.

"If people are worried about their young dogwoods or cherry trees, pond netting, or any kind of netting where the holes are small enough [so that] a cicada can't get through, should work," said Abbundi. "But we really don't feel people need to panic about it."

American Plant Food nursery recommends two products to clients concerned about young trees in the six- to ten-foot tall (two- to three-meter-tall) range.

"Pond netting, which is black and fades somewhat into the background, and spun poly-olefin, which is white and typically used as a row-crop cover, will both work. You don't have to wrap until the cicadas have emerged," Baker said. "There's a five- to ten-day lag before the females start laying their eggs."

Wrap the trees like a giant lollipop, covering the canopy and securing the netting beneath the lowest branches and securing it to the trunk.

To wrap or not to wrap is really a judgment call, Baker emphasizes. "You are going to see evidence of their activity, and if seeing the damage is going to bother you, wrap them."

"I have two peach trees at home that we planted several years ago, and now they're about six feet [two meters] across and ten feet [three meters] high, and I wouldn't worry about them," Shauff said. "But a couple of years ago, at 5 feet [1.5 meters] high and 2 feet [0.6 meters] wide, I would have netted them."

Unless you own a fruit orchard or a tree nursery, spraying is not recommended.

"Chemical control for adult cicadas is difficult, not 100 percent effective, and typically winds up killing good bugs in the process," advises Natorp, an Ohio-based nursery, in a brochure prepared for the 2004 emergence.

Don't prune your trees until the cicadas have come and gone; think of them as nature's own pruning shears. Some nurseries suggest holding off on planting young hardwood and fruit trees until the end of June.

Cicada Benefits

Gene Kritsky, who is about to publish a book on cicadas, wants people to welcome them with open arms.

"There are all sorts of benefits to cicadas," he said. "When they emerge the holes they create provide a natural aeration of the soil, moving more dirt than earthworms will. The holes persist, allowing more water to get to the roots, which is good if you're in a drought. [Dead cicadas are] a great fertilizer, providing nitrogen and potassium, putting a big chunk of nutrients back into the soil. And [cicadas] provide a natural pruning, so that the following year you get a greater yield of acorns, blossoms, or fruit, depending on the tree."

On the down side, when billions of cicadas die, the smell can "get quite funky for a while; kind of like bad limburger cheese," Kritsky said.

If you have a tiller to help turn the ground, or even a rake, to help bury dead cicadas, your garden will reap the benefits in the following year. Also, if you're in an area likely to be hit hard, you might want to keep your snow shovel handy to assist in removing them.

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