Why is there netting covering some of your neighbors’ trees? Blame the cicadas

Residents strolling through parts of the Midwest and Southeastern U.S. might be curious about an increasingly common sight cropping up in the neighborhood: trees covered in thin, diaphanous netting.

(NEXSTAR) – Residents strolling through parts of the midwestern and southeastern U.S. might be curious about an increasingly common sight cropping up in their neighborhoods: trees covered in thin, diaphanous netting.

They can blame the cicadas for that.

Cicada netting, or cicada control netting, is one of several methods for protecting more delicate trees or shrubs from harm caused by the insects. They work by keeping the cicadas out, and essentially forcing them to lay their eggs in the branches or twigs of hardier trees.

“They’ve got little saw blades at the end of the females’ abdomen,” Tennessee Tech University professor and horticulturist Dr. Douglas Airhart told Nexstar’s WKRN. “She cuts a slit [in the twigs], lays three or four eggs, moves on, cuts another slit. So, those slits puncture the water system within the tree, the outer branches, the outer limbs of that branch, start to wilt, and they’ll turn brown.”

The damage caused to the branches is known as “flagging,” and although it may be unsightly, it usually won’t kill the tree, unless the cicadas are targeting younger, more delicate varieties.

“A young tree could potentially get most of its branches affected so that could overwhelm the tree,” said Chris Hartley, of the Sophia M. Sachs Butterfly House at the Missouri Botanical Garden, told Nexstar’s KTVI.

Trees that were planted or started growing less than a year ago are most vulnerable, Hartley said.  

The U.S. Forest Service adds that certain types of trees — specifically hardwoods including oak, hickory, apple, birch or dogwood — tend to be most attractive to egg-laying cicadas.

“How much damage cicadas do depends on a tree’s size and age. Large trees may have multiple branch tips destroyed but will survive, while small trees can be killed by ovipositing females,” the service writes.

Aside from netting, other methods of deterring cicadas from vulnerable trees or bushes include wrapping foil or special tape around the trunks of the trees, to deter cicadas from climbing up into the branches, according to the Missouri Department of Conservation. But that doesn’t protect against any flying cicadas who could target the trees from above the trunk.

The experts say concerned homeowners will likely want to invest in tree netting for peace of mind, or, as Airhart told WKRN, even shade cloth, tobacco cloth or cheesecloth.

The netting can’t have openings “much bigger than a quarter-inch hole, though,” Airhart said.

“If you can get your little finger barely through it, that should be satisfactory,” he said, advising against any netting that’s big enough for a thumb to fit through. “They’re smaller this year than they will be next year. So they might be able to get in there and do some damage.”

Trillions of periodical cicada from broods XIX and XIII are in the process of emerging from the ground, bringing their numbers, and their noise, across portions of the southern and midwestern regions of the country. The XIX and XIII broods, which emerge every 13 and 17 years, respectively, may begin returning to the ground as early as June (depending on where they emerged), though some — especially Brood XIII cicadas that emerge later — are projected to stick around well into the summer.