Where are they now?
As of August 2017 the spotted lanternfly had been positively identified in many areas of Berks, Bucks, Chester, Lehigh, and Montgomery Counties in eastern Pennsylvania. This map shows confirmed locations (red) and trap locations where no spotted lanternflies had been caught (green) up to August 2017.
Related: What Makes An Invasive Species “Invasive”?
What do Spotted Lanternflies look like?
Adults (summer through frost) are inconspicuous spotted, brownish-grey plant hoppers about 1" to 1¼" long. Inconspicuous, that is, until they hop or take flight and show off their bright orange-red and white underwings. There are no look-alike insects in the eastern U.S., so once you see those underwings, you know what you are looking at.
In fall, starting in September in Pennsylvania, females lay masses of 30-50 tiny eggs on tree trunks, rocks, picnic tables, and pretty much any other solid object they can find. Egg masses are about ¾"-1" wide and 1¼" - 2" long. They are shiny at first, but soon dry and look like dabs of pale grey mud.
In the spring, those eggs hatch into tiny, 1/8"-inch, black and white, non-flying feeding-machines called nymphs. As the spring progresses, the nymphs pass through four stages, or “instars,” getting a bit larger each time. The first three instars are black with white spots, the fourth instar stage is orange with black and white spots about ½"-long.
In early summer the first adults begin to appear, and the cycle begins again.
Related: Why You Should Never Squish A House Centipede—Even If They Do Freak You Out
What does Spotted Lanternfly damage look like?
As they feed, the insects excrete a sticky substance called honeydew, which is rapidly colonized by sooty mold, turning leaves, stems, and trunks black. It also attracts ants, wasps, and other insects that feed on the sweet substance. You may well notice these symptoms before you see whatever insects are releasing the honeydew, so pay attention and investigate further if you notice sooty mold or a sudden influx of ants or wasps (other sap-sucking insects such as scale also produce honeydew, so these symptoms are not unique to spotted lanternflies, but they are always important to investigate, as early treatment can often prevent things from getting out of hand).
Check out the video below for some unexpected health benefits of gardening.
As eggs hatch in the spring the nymphs use their piercing mouthparts to suck the sap out of stems, leaves, and even the trunks of a wide range of different trees and shrubs (at least 70 different plants have been shown to appeal to them). Feeding can cause localized damage, stunted growth, reduced yields, or even death of the entire plant.
As the summer progresses the winged adults become more mobile, and head off in search of what appears to be their preferred host, the tree of heaven (Ailanthus altissima).
Related: The Shocking Reason Behind Dead Forests Across The Midwest
How to stop them
Don’t bring anything onto your property from an area where spotted lanternflies have been found—as of this writing, that includes a section of eastern Pennsylvania (here’s a map as of August 2017). This includes firewood (a major transferrer of many invasive pests and diseases), grapevines (including wreaths and other craft items), living trees and shrubs, Christmas trees (or at least be sure to burn your tree soon after Christmas to destroy any egg masses), rocks, outdoor furniture, equipment or vehicles parked for more than a little while, or anything that was stored outside, especially from September through frost (egg laying season). Anything parked or stored near a tree of heaven is especially risky. Obviously, you are going to have to drive your vehicles, and perhaps move other items, but before you do be sure to check all surfaces, including sheltered gaps and cracks, for adults and egg masses (scrape off any you find and destroy them; see below for how).
If you have spotted lanternflies, or live in an area where they have been identified, take the same precautions before taking anything off your property to another location.
Related: How To Stop Stinkbugs From Invading Your Home
Destroy egg masses
In fall and winter, learn how to recognize egg masses, arm yourself with a scraper (an old credit card works) and jar or plastic bag with a little rubbing alcohol in it, and go hunting. Scrape each mass off into the jar, where the alcohol will kill the eggs.
Once nymphs start to hatch in the spring they travel up and down the trunks of trees. Wrapping a wide strip of brown paper snuggly around the trunk and coating it with an insect trap adhesive such as Tangle-Trap creates an efficient trap, which can help reduce the population. Replace traps every two weeks until mid-July. This guide includes details on sticky trap use, as well as other control strategies.
In spring and summer, as a last resort for saving a crop or killing off a localized infestation you may want to try an organic insecticide, such as neem tree (Azadirachta indica) oil, Azadirachtin (a product derived from neem tree oil with no fungicidal action), or Pyrethrins (derived from Chrysanthemum cinerarifolium). None have yet been labeled for spotted lanternflies, so you will have to experiment. Please use organic insecticides carefully (follow all label cautions) and in limited areas, as they can kill some beneficial insects as well as pest.
Remove their favorite homes
As noted previously, tree of heaven (Ailanthus altissima), appears to be the host of choice for adults to feed and lay eggs on or near. These fast-growing, and generously-seeding, trees are classified as invasive in many States, and their role in the insect's lifecycle is one more reason to hate them. Getting rid of them once you’ve got them can be challenging, so learn to recognize them and go scouting for seedlings each year, pulling any you find.
Once you have trees, you have your work cut out for you, because the tree spreads predominantly by sending up new plants (suckers) along its wide-spreading roots—as far as 90 feet away in all directions. Sadly, the best way to stimulate root sucker production is to cut down the main tree, so eradicating an established tree or patch involves cutting down the trees and then revisiting the area—frequently—for up to five years to remove every single sucker that pops up (there will be hundreds and they can grow 15 feet in their first year if not removed or killed promptly). Failure to control the suckers will result in a thick patch of hundreds of trees, so this is not something to be undertaken lightly.
Organic herbicides, such as BONIDE BurnOut (citric acid and clove oil), Avenger Weed Killer (d-Limonene [citrus oil] and castor oil), and SaferGrow Weed Zap (clove and cinnamon oil), may offer some help with controlling small, leafy, actively-growing root-sprouts. This guide includes information on identifying tree of heaven (and a few other trees you might confuse with them) and dealing with it.
Note: Many tree of heaven eradication guides, including the one linked above, recommend spraying cut stumps with herbicide or even hacking holes in the bark of mature trees and spraying herbicide in those. Since organic herbicides break down rapidly and are not absorbed into the plant, they are unlikely to have any effect for these uses, only on small, leafy, actively-growing root-sprouts.
Related: 3 Reasons To Never Plant Butterfly Bush Again
Save a “trap tree”
One potentially useful strategy to help control spotted lanternflies is to allow a single male tree of heaven tree to remain on your property and use an insecticide to kill the insects that feed on it (cut female trees to prevent seed formation). The most effective insecticides for this purpose are synthetic insecticides, that are systemic (absorbed by the tree and remain there, just waiting for an unwary insect to take a sip of poisoned sap). Organic gardeners do not have any systemic insecticide options, but you may be able to keep a few suckers pruned low enough so that you could spray the entire thing with one of the organic insecticides listed previously in this article periodically (check the product’s label for frequency) from mid-July through frost.
OK, this is pretty experimental, but if you have a tree of heaven tree or two and you would like to be rid of but would prefer to avoid setting off an explosion of root suckers to fight for the next five years, you might want to give this alternative method a try. It involves inserting commercial oyster mushroom plugs (wooden dowels impregnated with mushroom spores) into the living trunks and waiting a few years. The idea is that the oyster mushroom fungus slowly weakens and eventually kills the tree (without triggering the root sucker production explosion that cutting it down would) while turning your problem tree into a food factory. What’s not to like?