The invasive spotted lanternfly, and its gross honeydew, is here to stay

The nymphs are starting to emerge across Maryland.

Maybe you’ve seen them on a blooming rosebush or the twisting, climbing vine of a honeysuckle. Most likely, you’ve seen the tiny, black-and-white babies on tree of heaven, an invasive deciduous tree that grows quickly and is difficult to kill.

No matter where you noticed the spotted lanternfly nymphs, they’re a sign of what’s to come. Experts said they expect a swarm of the bugs — which take on a dramatic red coloring when they’re grown — just like last year in Maryland.

And the invasive, hoppy bugs are here to stay.

“Eradication is not the goal. Management is the goal,” said Jessica Boyles, the spotted lanternfly program coordinator at the Maryland Department of Agriculture.

The bugs, which were first noticed in the United States in Berks County, Pennsylvania, roughly a decade ago, have spread to every corner of Maryland. All but four counties in Maryland are under a spotted lanternfly quarantine from the MDA.

Michael J. Raupp, a professor emeritus of the Department of Entomology at the University of Maryland and “The Bug Guy,” said he thinks lanternflies will not be vanishing soon. They have established in the region and join the “cadre of invasive species that will be with us, just like the stink bugs and emerald ash borers,” he said.

It is hard to say just how large the swarms will be this year. Boyles said the population density of the spotted lanternfly varies by county.

“I know Baltimore County and Baltimore City were very, very positive last season. I would expect to see something similar this season,” she said.

Will spotted lanternflies hurt my garden?

The good news is this: Spotted lanternflies do not bite or sting. When they’re fully grown, they take on a gorgeous bright red hue and can look almost like a butterfly or a moth. They’re not very good at flying, and they clumsily hop around, much like cicadas.

They’re also not harmful to most gardens or crops. Boyles said she’s not aware of any reports of a spotted lanternfly killing a garden or forest tree.

Kathy Jentz, the editor of Washington Gardener, said most gardeners in her circle aren’t worried about the insect. Jentz said she thought the state’s warnings about sequestering lanternflies kept the populations from growing too much.

Raupp said the real issue in Maryland has been the bugs wreaking havoc on wineries and vineyards.

Joe Fiola, a viticulture specialist with the University of Maryland Extension, said there’s been pressure on grape growers in the state from the spotted lanternfly.

“It’s one of the toughest things we’ve had to manage,” he said. It can also be expensive, but the alternative is losing the crop. “You can’t afford not to manage them,” he said.

The lanternflies appear to be drawn to grapevines because, late in the year, after the harvest, they become an easy meal. As the grapevines prepare for winter, Fiola explained, the sap inside the plant is pushed down into the roots, creating high pressure that makes it easy for a lanternfly to stick its face in and drink up.

“This is the one commercial crop it hits,” Fiola said.

Despite the pressure, Janna Howley, executive director of the Maryland Wineries Association, said the industry in Maryland is growing. At least “a couple hundred” new acres of grapes have been planted in the last few years, she said.

Spotted lanternfly problems: What is honeydew?

Raupp said there are early reports that eating the insects can make pets sick, so don’t let Fido chow down on a spotted lanternfly buffet.

Perhaps the biggest concern for non-vintners in Maryland is the potential for lanternflies to climb high into the trees and rain down their waste product, charmingly called “honeydew.”

The waste product is essentially sugar and water. They produce “gallons and gallons” of the stuff, according to Raupp.

“When you stand under a tree with spotted lanternflies, it will rain on a sunny day,” he said.

The proliferation of honeydew is a twofold problem. First, it can attract stinging insects such as wasps. Second, it can lead to the growth of sooty mold, a dark, sticky fungus that harms plants by limiting their ability to photosynthesize.

That honeydew can also lead to unfortunate situations for anyone unlucky enough to live near a cluster of trees — especially the tree of heaven, which lanternflies favor.

Rick Wilson, who lives in Baltimore’s Remington neighborhood, said there are five or six tree of heaven plants growing behind his tiny rowhome. Because the trees are all around, he said, lanternflies have mostly left his garden plants alone — but in his backyard, the presence of so many lanternflies swarming in the trees made it feel like it was “constantly raining.”

“I did not, my neighbors, we did not use our yards. June through September [last year], we didn’t go outside,” he said. The bricks in his backyard are still covered in the black sooty mold.

The lanternflies are likely drawn to tree of heaven because it is native to the same parts of Asia. The plants are hardy, grow fast and very hard to kill.

“I never wish evil on any living thing, but I would not miss the tree of heaven if it were to disappear,” Raupp, the professor emeritus, said. He added that removing tree of heaven from yards would be a critical step in managing lanternflies.

The trees must be killed with a “systemic herbicide,” because the plant can regrow from anywhere in its root system. Pennsylvania State University Extension has guidelines for controlling tree of heaven.

Are they here forever?

The short answer is yes. The slightly longer answer is yes, but the population may stabilize — meaning the huge swarms of last year (and likely this year) are not forever.

Raupp said he’s talked to colleagues in Pennsylvania, where birds and other insects are starting to eat the lanternflies. He thinks the population will decline and stabilize within three or four years, “like we’ve seen with other invasive pests like the stink bug.”

Boyles said she has heard rumors that folks in Harford and Cecil counties — where the bugs first entered Maryland — have seen declining populations.

She said it’s useful for people to report spotted lanternfly sightings to the state, so the Maryland Department of Agriculture has more information about the population spread and can best determine where to send workers to remove the insects.

And, Boyle said, she would “greatly appreciate it” if people continued to kill the bugs when they can, whether it’s through mechanical removal (like a shop vacuum on a tree), stomping them or spraying targeted insecticides.

Raupp had a slightly different point of view. He said you should remove tree of heaven if you can and suggested using Organic Materials Review Institute-approved insecticides to kill spotted lanternflies on garden plants — but he said stomping individual, adult lanternflies is “nothing more than retribution.”

If you want to stomp on the bugs to stem the population boom, “you could,” Raupp said. “And, if you imagine that when you spit in the ocean you could turn back the tide, you could do that as well.”