Chinese lanterns, bright and cheery, can lend a festive air to an evening out on the patio. As far as I know they are harmless. Chinese spotted lanternflies are also bold and colorful, but they do cause harm, and lots of it. And if they’re in your backyard trees, the patio might get covered in black sooty mildew from their depredations.
Spotted lanternflies were unknown in North America until 2014 when a Pennsylvania landscaper found them on his back lot. Evidently, one or more lanternfly egg masses arrived on a shipment of stones from China. Who knew the Keystone State was that short on rocks? Had we been aware of this deficit, we would have sent some rocks down there and saved a lot of grief.
If only it were a laughing matter. The spotted lanternfly (SLF) is a significant pest of numerous tree species, including pine, as well as of grapes, tree fruits and non-woody plants. In short, just about anything green. Should it spread, it represents a serious threat to many agricultural crops.
Prolific breeders, SLF females lay yellowish-brown (later turning gray), foam-like egg masses similar to those of the gypsy moth. This is probably how they stowed away on that pallet of stone. The juveniles or nymphs look nothing like the adults. Black with white spots, they molt several times before maturing, becoming red in the last phase of their “childhood.”
Its name can be confusing since the adult looks very much like a moth yet it’s called a fly. But it’s not either. It is a hemiptera, related to walking-stick bugs and giant water beetles. Like all hemipteras, spotted lanternflies have piercing mouthparts, and they use these to great effect draining sap from plant tissue.
While some of the worst invasive pests such as Asian longhorn beetles and emerald ash borers have harmless native doppelgänger, the lanternfly is nearly impossible to confuse with any other insect. Here is a USDA description: “Adults are about an inch long by a half-inch wide, with large, visually striking wings. Forewings are light brown with black spots in front and a speckled band at the rear. Hind wings are scarlet with black spots in front and white and black bars at the rear. Abdomen is yellow with black bars.”
If you’ve heard of tree-of-heaven or Ailanthus you know that it’s an invasive weed-tree from Asia, so bad it makes boxelder look desirable by comparison, if you can believe that. Unfortunately for us, lanternflies attack Ailanthus before any other species. One would think this is a good thing: an invasive pest takes out an invasive plant—problem solved.
I say unfortunately because SLF will feed on a tremendous range of hosts when it runs out of its favorite food. Since Ailanthus does not grow in New York’s northern tier or in most of Canada, to the best of our knowledge, the lanternfly would move right to other desirable species without first showing up on tree-of-heaven. We wish it preferred tag-alders, something we have in abundance.
Where Ailanthus does grow it can serve as a sort of early-warning device since that’s where SLF will show up first. In addition, it may be possible to use tree-of-heaven to fight SLF. Infested Ailanthus could be treated with a systemic product that would kill any lanternfly that feeds on it.
For obvious reasons, Penn State entomologists have taken the lead in researching SLF, and are working in conjunction with federal and Pennsylvania State Departments of Agriculture. Among other things they want to find its natural enemies, be they predators, parasitoids or diseases. While one parasitic wasp species from China holds promise as a natural control agent, its release here is a long way off, possibly over a decade.
The USDA now considers New Jersey, Delaware, Virginia, and Pennsylvania to be SLF-infested states. Many quarantines are in effect, including Christmas trees.
Experts once thought that lanternfly could not complete its life cycle without feeding on Ailanthus at least once, which meant we were off the hook in northern NYS. Now that early belief has been called into question. Furthermore, SLF has been found in at least five locations in New York State in 2018, including two in Monroe County, one in Yates County, and two downstate. This makes it all the more important that we keep SLF out of the region. We need to spread the word about lanternfly and how to identify it. Citizen-science projects could be invaluable.
SLF doesn’t fly far, but as noted, it can relocate by way of its egg masses, which the female SLF will lay on any smooth surface. At least in Pennsylvania, eggs are laid into the late fall and early winter, and while the masses are shiny and brownish when fresh, they darken and become duller over time and are harder to see. Visitors to quarantined area could unknowingly transport SLF egg masses on their vehicle chassis or other hard-to-see places.
Paul Hetzler is a horticulture and natural resources educator with Cornell Cooperative Extension of St. Lawrence County.