Invasion of the Spotted Lanternfly
All photos courtesy of Swarthmore resident Colin Purrington. Check out Colin’s other lanternfly photos on Flickr.
Young lanternfly nymph
Older lanternfly nymph
Adult lanternfly
It sounds like the title of this summer’s blockbuster movie, but it’s not. It’s reality TV, and whether or not you have seen them in your yard or garden, you can be almost certain they are lurking there. They are an invasive insect called the spotted lanternfly (Lycorma delacatula) – SLF for short. They’re currently morphing through one of several nymph stages. Very soon there will be thousands of adult lanternflies in our community. They attack trees, vines, and shrubs, and there isn’t much we can do about it.
But there are some actions we can take. Mostly that means figuring out the best way to kill them.
If you have – or suspect you may have – an SLF infestation, you have several options for fighting or eliminating them. But there isn’t necessarily one best method, and some methods are controversial. Anyone intent on killing lanternflies must balance the effectiveness of a given method against potential collateral damage – to other insects or animals, or to the environment — and the time, effort, and cost.
Here are a few facts about the bugs:
SLFs are native to southeast Asia, and were first seen in Pennsylvania in 2014. They have spread through the mid-Atlantic states (New Jersey, Delaware, Pennsylvania, Maryland, and New York).
Pennsylvania and Delaware have imposed regulations requiring certain items that may be infested to be kept quarantined for a period before moving them from region to region. Delaware County is among 26 eastern Pennsylvania counties with an SLF quarantine.
Young nymph SLFs are black with white spots, and about the size of a pencil eraser. Older nymphs are red with black and white spots, and about the size of your pinky fingernail. Adults look like moths (they aren’t), and are a buff pinkish gray with black spots and crimson forewings that flash conspicuously when they fly. As insects go, they are really quite attractive.
These insects are called “planthoppers” because, in all stages of development, they jump — quickly and well. Nymphs cannot fly, though adults can. They don’t usually fly far, though, or particularly well.
SLFs’ primary host tree – the one that both nymphs and adults prefer to feed on – is the tree of heaven (Ailanthus altissima), which is a fast growing, invasive species that’s fairly easy to identify. If you have this tree in your yard, cutting it down can help control the pest.
Specialized mouthparts enable the lanternflies to pierce the outer stem of a plant or the bark of a tree to access the sap. When they feed on trees, they pierce the phloem: the thin layer under the bark that transports the sap. If enough SLFs attack a plant or tree, this can weaken or kill it.
Lanternflies “eat” more than they need, then deposit the surplus amount, in the form of a sugary, sticky residue called “honeydew,” on the tree or plant. This often collects on the bark and at the base of infested trees, promoting the growth of fungus that further damages the tree.
Spotted Lanternfly Life Cycle
Eggs that have overwintered hatch between early spring and May. The immature lanternflies, called nymphs, pass through several stages (called istars), molting and growing larger each time. They reach the adult stage in mid-summer.
The adult females start laying eggs in September and continue into the fall. They may lay eggs on almost any surface, including cars, lawn furniture, and old cinder blocks. They deposit the eggs in several bumpy parallel rows, then encase them in a waxy protective layer. This looks like someone smeared a small patch of grayish-brown creamy peanut butter onto some surface.
When cold weather sets in, all the adults die. Then, when the eggs hatch in the spring, the cycle begins once more.
Right now, the larger nymphs – the ones that are red, black, and white – are appearing. Soon the adults will show up, and they’ll show up in large numbers. While they prefer the tree of heaven for their dinner, they will attack many other species of plants and trees. And the SLF don’t just enjoy feasting on the ones in our yards. They damage commercial crops, vineyards, and orchards as well.
Spotted lanternflies have few natural predators. Those they do have, such as praying mantises, are not present in large enough numbers to control the invaders.
Options for Combating SLF
One effective way to kill the nymphs when they are still in the crawling stage is to wrap sticky bands around your trees and hold them in place with tacks or push pins. This traps them as they crawl up or down the trunks. Since the nymphs will not be in the crawling stage much longer, it is somewhat late in the season to follow this approach right now.
Charlie Devaney at Swarthmore Hardware has been selling rolls of flypaper for this purpose, but so many homeowners are using it he has had trouble keeping it in stock. Check to see if he has gotten another shipment in this week. If you didn’t wrap your trees this year, think about doing it next spring.
Sticky bands are controversial, because they have a serious drawback: They pose a threat to beneficial insects, birds, and other small creatures, which can also get caught in them. Woodpeckers, for example, will be attracted to insects that get trapped in the bands.
So, two things. First, you don’t need a wide band around your tree trunks. A 4-inch-wide strip is ample. This reduces the chances that beneficial insects, a bird, or some other small animal will become caught in the band.
Second, wrap chicken wire around the sticky band and hold it in place with push pins. Chicken wire is not difficult to cut and use. If you find you have to buy more than you can use, share it with neighbors and on Nextdoor. Don’t imagine that this is unimportant. If you use the sticky bands, use the wire.
If you want to avoid using sticky bands because of the collateral damage, or if you want to kill the lanternflies on bushes and shrubs that can’t be wrapped with a sticky band, Swarthmore resident Reisa Mukamal suggests a couple of alternatives. “A soap-mixture spray is effective and easy,” Mukamal says. “Mix equal parts Dawn dish detergent (really any brand will do) and water in a spray bottle. Spray this directly on the lanternflies. It kills them quickly.” Plain white vinegar also works, she says, but it can be more damaging to the plants that are being sprayed.
There are two downsides to the spraying approach. First, residents cannot stand in their yards all day with spray bottles in hand looking for undesirable bugs. Second, detergents are pollutants. They often contain multiple additives, and these will eventually pass into the ecosystem. For many residents, this concern may override the usefulness of the spray.
Pesticides or insecticides are certainly effective but must be handled very carefully. They can damage the environment, and they will also kill a broad spectrum of insects, including beneficial ones, so many experts and homeowners discourage this approach. Use them sparingly, choose the least toxic option available, and, if possible, spray after the host plant’s flowers are no longer in bloom, to avoid poisoning pollinators.
Penn State Extension is among those concerned. Their website cautions that homemade remedies, often touted on the internet, may “have the potential to harm humans, pets, and plants, do not come with precise directions, [and] may not be effective,” and that “their use can violate federal law.” They remind homeowners that the pests are dangerous neither to people nor to homes: “If spotted lanternflies are crawling around your home or yard, they have likely found a plant or tree nearby to feed on, such as tree of heaven.”
As mentioned earlier, if you have any trees of heaven in your yard, you can cut them down to thwart the bugs. Or you can cut all but a couple of them down and use the one or two remaining as an SLF lure and trap. Target and kill the adult lanternflies that gravitate to these trees. A vacuum cleaner can be a quick and effective solution, especially for the adults. Seriously.
Another SLF deterrent — perhaps the one with the smallest downside — is to go on a hunt for the egg cases and destroy them. This can be a family affair. Of course, you have to do it after the eggs have been laid in late fall, and before they start to hatch in early spring. And be aware that they camouflage well, especially as they weather over time, so they can be difficult to detect. But studying photographs of them can help.
To destroy the eggs, Penn State Extension suggests putting alcohol or hand sanitizer into a sandwich bag and scraping the egg cases into the bag. Or you can smash them with a small rolling pin. Or simply scrape the egg case off whatever surface it is attached to and crush it under foot. (Don’t just scrape them off. Crush them. But beware, the eggs are gooey.)
One Biologist’s Approach
Colin Purrington, a Swarthmore resident and former biology professor at Swarthmore College, has an informative and sometimes humorous post about SLF on his blog at swat.ink/purrington-on-slf. He includes a link that explains how to make and use a “circle trap,” a more complicated approach to killing lanternfly nymphs, but without the downsides of other solutions mentioned here. He also suggests hanging a flyswatter somewhere handy and killing them with that.
Purrington is skeptical that SLFs are worth the time many residents are putting into fighting them. “Spotted lanternflies do not seem to be killing trees,” he said, adding, “I certainly wish we didn’t have them.” He has also read reports that “even if you wipe out thousands of nymphs with tape, there are likely tens of thousands that will take their places.” He concludes, “It just seems futile to me, personally. And areas that had horrible infestations two years ago are reporting much lower numbers now, so I think something (virus, bacteria, fungus, or combination) is taking them out.”
Scientists continue to learn more about SLF, and what we know next year may change our thinking in some way. But in the meantime, choose the most effective methods to kill the pests while minimizing damage to the environment or to beneficial creatures.
SLF Quarantine
The Pennsylvania Department of Agriculture quarantine requirements that apply in many eastern counties are intended to slow the spread of SLF. Residents who want to move items that may be infested – such as boats, firewood, vehicles, playground equipment, camping gear, and garden equipment – out of the areas covered by the quarantine must first follow a checklist which includes learning to recognize the stages in the SLF life cycle and physically checking the items for bugs or egg cases before moving them. Businesses are required to have a permit to move vehicles or products out of the quarantine zone, and must submit to inspections for SLF.
If you want to investigate SLF further, go to the Penn State Extension website, swat.ink/PSU-on-SLF, where you can sign up for their SLF newsletter, or to the Pennsylvania Department of Agriculture website, swat.ink/pa-ag-SLF.
All these measures combined may help slow the spread of the spotted lanternfly. However, they will probably have to be implemented not just this year, but for years to come. That means this reality TV show is guaranteed a long run.
David Page is chair of the Swarthmore Tree Committee.
