BEAUTIFUL PEST:  The spotted lanternfly, first seen in New Jersey in 2018, has arrived in Princeton, and its numbers are expected to increase rapidly. The destructive plant-hopper infests a variety of different trees and vines, and excretes a sticky fluid similar to honeydew that creates a sooty, moldy mess.

By Donald Gilpin

Just when you were enjoying spending time outside, socializing with social distancing guidelines in the open air during the pandemic, there’s another threat that might drive you indoors in the coming weeks.

The spotted lanternfly, a moth-like Asian plant hopper with bright red coloring and black spots, has recently been identified in at least six sightings in Princeton as part of Princeton’s BioBlitz. Though it has two pairs of wings, it jumps more than it flies. 

It’s an invasive species, destructive to crops and trees, especially maples, willows, and other smooth bark trees — at least 70 host species.  And spotted lanternflies are extremely annoying pests, according to Bob Dolan, mid-Atlantic territory manager of Rainbow Tree Care Scientific Advancement in Montgomery County, Pa. 

Not yet as pervasive in Princeton as it is in Pennsylvania, the spotted lanternfly was accidentally introduced and confirmed in September 2014 in Berks County before it spread throughout Pennsylvania and into neighboring states.

New Jersey spotted lanternfly populations were first discovered in 2018 along the Pennsylvania border, and they have been gradually spreading eastward through the western part of New Jersey. 

Adult spotted lanternflies buzz around in large numbers, sometimes thousands, Dolan described. “It can look like the whole bark of the tree is vibrating,” he said, and they produce a clear, sticky substance, honey dew, that provides a food source for a black, sooty mold fungus, damaging on sidewalks, vehicles, fences, decks, and yard furniture, as well as trees.

Wells Tree and Landscape CEO Dave Wells emphasized how fast the spotted lanternfly breeds and spreads. He mentioned that they were already numerous in Lambertville, and that many more would be coming this way in September and October. “Adult spotted lanternflies will start to appear in the next few weeks, and they will be a part of everyday life around here for a while,” he said.

Noting that they probably won’t kill larger trees, he continued, “They are piercing, sucking insects that will suck the sap out of trees, and they are going to feed and defecate and make a sticky black mess. You can see thousands of them on a tree at one time. On a willow tree in Lambertville I saw the entire trunk was covered with them.”  Wells pointed out that grape and fruit trees and vineyards are likely to have problems with the spotted lanternfly.

He continued, “Though they won’t kill larger trees, they will reduce the vigor, and they will be alarming. They will keep multiplying. The spotted lanternfly population will definitely continue to build. Each female lays about 100 eggs each year.”

Wells stated that the ailanthus tree, an invasive plant known as the tree of heaven, a weed tree, is
especially popular with spotted lanternflies. “Get rid of it fast,” he said. “Lanternflies love it.” The iNaturalist platform (inaturalist.org) can help with identification of the ailanthus tree and the spotted lanternfly.

Dolan emphasized that there are ways to combat this pest, but there is no repellent, “no way to put a dome around your property.”  As territory manager at Rainbow Tree Care Scientific Advancement, Dolan trains and helps companies to implement an insecticide treatment with a basal bark spray on the lower five feet of the tree. Applied after the trees have finished blooming, the insecticide will be absorbed and spread throughout the tree so that the lanternfly will die wherever it sucks on the tree.

Wells recommended that residents who see the spotted lanternfly call their local arborist or tree care specialist, who can help create a plan to manage spotted lanternflies. “They are probably not going to kill your trees, but some people can’t stand to see them around,” he said. “It comes to individual preferences. Some people will want to use an insecticide program. Others will decide to let it go.”

Wells expressed hope of a natural decline in spotted lanternfly, perhaps in two or three years. There are two naturally occurring fungi that can kill the spotted lanternfly, and a few beneficial insects — spiders, praying mantises — have been known to attack the spotted lanternfly, primarily in the egg stage. 

In the meantime, residents are urged to prepare for what Wells describes as a “gross, disgusting” encounter, as they remove any egg masses discovered, and destroy any spotted lanternfly insects they can.