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The truth about the spotted lanternfly
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UPDATE: This post was edited on Sept. 15, 2023, to reflect updated guidance for managing the spotted lanternfly and tree of heaven, and information about whether — and where — to report sightings.
By now, I’m sure you’re familiar with the spotted lanternfly and the havoc it can cause to our ecosystem. If you live in Connecticut, Delaware, Indiana, Maryland, Massachusetts, Michigan, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Virginia or West Virginia, you’ve likely seen them — or know someone with a story to tell.
If you live elsewhere, you still should pay attention because nature doesn’t respect municipal lines, so they very well could be headed for a garden, park, farm, vineyard or street tree near you.
Native to Asia, the invasive insect (technically, a “true bug”) has several life stages, beginning with a small, white-spotted black nymph that hatches in May or June.
Nymphs, which hop and jump when you approach them, grow in size from birth through July, thanks to a steady diet of vascular phloem tissue from plants and trees, then turn red (with black markings and white spots) before morphing into admittedly beautiful moths.
Like vampires, they insert their piercing, sucking mouthparts into tree bark and drain its sap. It’s not uncommon for infestations to be so severe that the gooey fluid drips visibly from holes all around the tree.
As with all living things, what goes in must come out, so after gorging themselves on sap, lanternflies excrete a sticky substance called honeydew, upon which a black fungus called sooty mold tends to grow. Sooty mold blocks sunlight from reaching leaves, inhibiting photosynthesis (the process in which plants create food for themselves). Essentially, trees and plants can then starve to death.
From September through December, female moths deposit egg masses containing up to 50 eggs apiece on outdoor surfaces like trees, cars and patio furniture, then protect them with a waxy coating that looks like mud. Those camouflaged egg masses remain in place — usually unnoticed — until May or June, when they hatch and repeat the cycle, increasing their numbers each year.
Checking cars for these blobs is essential to avoid transporting them to other locations.
I’ve seen some misinformation on social media lately that I’d like to clear up. One commenter, in particular, asserted that lanternflies don’t pose a threat because they only eat the weedy tree of heaven (Ailanthus) and grape vines. And, he said, since he didn’t have the tree — and didn’t care about any winery’s business success — all the hubbub was overblown.
This is simply untrue.
The invasive tree of heaven is, in fact, the pest’s primary host plant, but lanternflies will also feast on walnut and other hardwood trees, including maple, birch, willow, cherry, apple and peach, plus hops and other crops, including but not limited to grapes. This is according to the USDA.
Removing the tree of heaven would go a very long way toward diminishing the pest’s numbers — BUT ONLY IF you do this in late fall, after you have removed and destroyed egg masses deposited on the trees (see how below).
The “moths” will die during the first frost, so they won’t be a problem next year. But, if left undisturbed, those egg masses, containing up to 50 eggs apiece, have the potential to increase the SLF population FIFTY-FOLD next spring.
So experts are now recommending that homeowners with trees of heaven on their properties leave those trees in place during spring, summer and fall, when they serve as trap trees, luring the insects away from other susceptible plants and trees, and providing a good indication of the extent of the SLF population in your area.
Then, remove and discard all the egg masses deposited on the tree by scraping them into a zipper-top plastic bag filled with hand sanitizer, sealing the bag and placing it into the trash.
THEN remove and discard the tree of heaven.
Inspect other trees and outdoor items, like patio furniture, grills, playsets, bricks, stone and stored firewood, for egg masses, as well, and remove and destroy them as above.
This new guidance offers the best hope I’ve seen for control so far.
Some states are asking residents to report sightings to their departments of agriculture so they can track the insect’s movements. Here in the New York metropolitan area, we’ve seen spotted lanternfly activity migrate east from NYC last year to Nassau County earlier this year and now to western and central Suffolk County. The east end has yet to see an infestation, but the region’s vineyards are bracing for what could be devastating activity next year.
If you see spotted lanternflies, kill them. Generally, most municipalities are asking folks to report their sightings. However, when officials in regions, such as here on Long Island (with the exception of the East End), are fully aware of infestations in their area, they may no longer request — or want — further reports of sightings.
So check with your state’s department of agriculture for instructions (an online search for “spotted lanternfly” and your state’s name plus “department of agriculture” will provide what you need to know).
I haven’t seen a lanternfly yet, but my neighbors have, so it’s probably only a matter of time before I do.
I tend to escort insects outdoors when I find them in my house, so it won’t be easy for me to “stomp” a lanternfly, as officials advise, but I will because there’s too much at stake. And I hope you do, too.
Please share this post with your gardening friends to help keep them informed.
📬 Ask Jessica
DEAR JESSICA: Four years ago, I started Frangipani trees from 4-inch cuttings, and they rooted and grew well. One is now 5 feet tall, and the other is 3 1/2 feet. I have kept them both indoors, where they get very good sunlight. Why don’t they produce any flowers? —Joseph Ferraro, New York
DEAR JOSEPH: Frangipani plants, also known as plumeria, are beloved for their sweetly scented flowers. I’ll never forget my first encounter with them on a trip to Hawaii many years ago — their fragrance is intoxicating, so I can understand your disappointment.
The plants require bright, direct sunlight and deep watering when their soil dries. They also need some humidity, as they hail from the tropics. Since they have been thriving in your home for 4 years, I assume you are caring for them properly.
However, Frangipani are heavy feeders. Although it can be tricky to get them to bloom indoors, they won’t stand a chance without sufficient fertilizer.
During the active growing season, from spring through fall, you should fertilize them every week or two with a product high in phosphorus and low in nitrogen. Check the package for a three-digit nutrient ratio with a low first and high second number. In this case, the third number isn’t important.
And send me a photo when they bloom!
💡 If you do one thing this week…
Start saving vegetable seeds for next year. Here’s how.
👏 Sunday shoutout
Reader Jane Shelley shares this colorful shot from her garden in Wantagh, NY. “Flowers in my garden greet me in the morning, beginning my day with a smile!”
I can see why, Jane!
Send in your photo, and you could be featured next (bonus points if you’re in the picture!)
📰This week in my Associated Press gardening column
I write a weekly gardening column for the AP, so you might have seen my byline in your local paper (or news website) — wherever in the world you happen to be. In case you miss it, I’ll post the most recent here every week.
Last week: Annuals are the loyal friends every gardener can use, especially as the season winds down. Here’s why I learned to love them.
One week prior: Heat-tolerant plants and practices for a warming climate
You can read all my AP gardening columns here.
📚📺🎵 Random things I enjoyed this week
Inspired by a recent restaurant meal with my editor (thank you, Julie!) I made a batch of super-easy and unbelievably tasty vichyssoise (cold potato-leek soup) to help keep my daughter Justine nourished while recovering from oral surgery. And it was perfection.
I simmered 4 medium-sized, peeled and cubed potatoes with 2 giant leeks (white parts only, trimmed, sliced, soaked and rinsed) in 4 cups of water to which I added a tablespoon each of butter and Podravka Vegeta. (If you don’t have Vegeta, you can use a bouillon cube or substitute 2 cups of broth for half the water).
After 20 minutes, when the veggies were nice and soft, I pureed them in the blender in two batches, then added a cup of fat-free half and half (you can use cream or full-fat half and half if you prefer). Taste and adjust for salt and put it in the fridge until chilled.
It couldn’t be easier — or more delicious. Let me know if you try it!
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