WANING NEMESIS: The spotted lanternfly, in its full-grown adult state as it prepares to mate and lay eggs in September and October, is declining in numbers in Princeton, according to Municipal Arborist Taylor Sapudar. Residents are advised to keep on stomping and removing ailanthus trees.

By Donald Gilpin

In late August the New Jersey Department of Agriculture (NJDA) informed New Jersey residents that they no longer need to report sightings of the spotted lanternfly. The invasive insect is now present in all 21 counties of the state, but in Princeton the numbers are diminishing, according to Princeton Municipal Arborist Taylor Sapudar.

“I have not seen high populations in Princeton at all this year,” Sapudar said. “It’s much better than last year. I might have seen one or two adult lanternflies this year, but in years past I saw them everywhere.”

Sapudar noted that when the spotted lanternfly first appeared in New Jersey in 2018 it was only present in a few counties bordering Pennsylvania. The NJDA wanted to have people report it so it could help control and prevent the spread and coordinate treatment resources.

Foresters from Berks County, Pa., where the spotted lanternfly first appeared in this country in 2014, have been in communication with Sapudar, and have reported significant population decreases. “I suspect that it is a combination of residents removing the tree of heaven (ailanthus altissimo), the spotted lanternfly’s preferred food source, and residents treating host trees with insecticides,” Sapudar said. There is also some evidence that spotted lanternfly populations tend to increase in the first two years after their first appearance, then level off in the third year, and decline after that.

Sapudar applauded Princeton residents’ efforts so far. “Management is working,” he said. “Keep on stomping. Remove ailanthus trees. Work with a certified arborist to identify host trees.”

Urban areas in New Jersey like Jersey City, Camden, and Newark have more spotted lanternflies than Princeton because they have more ailanthus trees, Sapudar noted. “When I was first getting calls [three or four years ago] people would say, ‘They’re everywhere,’ but I’d walk the property, and it’s typically just a couple of common host trees that they prefer. That’s where insecticide can be helpful,” Sapudar added.

He continued, “The ailanthus, their prime host, is a tree that the DEP recommends to be removed anyway. If the spotted lanternfly is on a more desirable species like a red maple or river birch, that’s where you’ll want to use other methods of treatment.”

Sapudar recommended that residents avoid using “sticky traps” on the trees. “The sticky trap doesn’t discriminate,” he said. “It will catch anything. There are a lot of beneficial insects, and I’ve even seen small mammals attached to the sticky trap.”

The spotted lanternfly is not going away anytime soon, Sapudar said. In addition to New Jersey and Pennsylvania, it has been found in nine other states: Connecticut, Delaware, Indiana, Maryland, Massachusetts, New York, Ohio, Virginia, and West Virginia.

Princeton — with its high density of trees, and still an abundance of ailanthus, as well as other tree hosts including black walnut, red maple, river birch, willow, and agricultural crops such as grapes, apples, and peaches — continues to be susceptible to the colorful pest.

Spotted lanternflies are not a threat to humans or animals, but they can be a messy nuisance, and they have the potential damage agricultural crops and hardwood trees.

To help manage the spread of the insect,  Princeton residents and business owners are encouraged to destroy as many spotted lanternflies and egg masses as possible. See princetonnj.gov/616/Spotted-Lantern-Fly for further information on how best to do that.

Spotted lanternflies have moved into the adult stage over the past two months and are easily recognizable with their two sets of wings, one pale gray with black spots and the other with bright red spots. 

Mating and egg laying take place in October, so this could be a critical time for management, according to the New Jersey Agricultural Experiment Station (NJAES) at Rutgers University. The first freeze will kill off the adults, but the eggs will survive to hatch new lanternflies next year.

The spotted lanternfly can lay egg masses on any flat surface, such as tree trunks, cars, picnic tables, and houses. Most of the egg masses on trees are found more than 10 feet above ground. Those egg masses, about one inch in size and containing up to 50 eggs, should be scraped and removed.  Female lanternflies can lay up to two egg masses.  Freshly laid egg masses have a light gray mud-like substance covering the eggs, while older egg masses change to a light tan color resembling cracked mud.

The spotted lanternfly is known as an invasive plant hopper, native to China, India, and Vietnam, and also established in South Korea and Japan, in addition to the U.S.

The spotted lanternfly has the potential to damage agricultural crops and hardwood trees, according to the NJDA. “The spotted lanternfly uses its piercing-sucking mouthpart to feed on sap from over 70 different plant species,” the NJDA website states. “It has a strong preference for economically important plants and the feeding damage significantly stresses the plants, which can lead to decreased health and potentially death.”

The NJDA website goes on to describe how the spotted lanternfly excretes honeydew (a sugary substance), which can attract bees, wasps, and other insects as it promotes the growth of sooty mold (fungi), which can cover a variety of surfaces.

The NJDA website urges, “If you see a spotted lanternfly, help us Stomp it Out!” Many common spray insecticides will kill spotted lanternflies, the NJDA notes, but use insecticides only with great caution. They can also kill bees and other helpful animals.

For additional information, visit badbug.nj.gov, another NJDA resource for people to learn more about spotted lanternflies.