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If You're Seeing Spots, Call for Help

Q. Well; this week's question may be the shortest we've ever used! Ed in Conshohocken, PA sent us a pair of photos and the brief note: "Do you know whether these are egg masses of the Spotted Lantern Fly?"

A: Well, are they?

I think so, but I urged Ed to send the photos to his local Extension office for confirmation—and to alert them if this newly-arrived invasive pest from Asia hadn't previously been found in his neighborhood. Because they're only in a very small part of the country—so far.

A year ago, I would have said that this pest was confined to one small corner of Pennsylvania where Berks, Bucks, Montgomery and Lehigh counties meet up. But now it's also been confirmed in Chester County; and in Delaware—the state, not the county. Officials pretty much agree that this will move from being a local story to one of national significance over the next few years; and they have made an unusually strong call for "citizen scientists" to assist in the effort to slow the spread.

But first, the basics. What does it look like?

It's almost impossibly distinctive. The adults are said to be about an inch long, although the one I saw back in the fall looked somewhat bigger. Two sets of wings. The ones near the head are grey with black spots, and the wings towards the rear are red with black spots. The head and legs are black, and the abdomen is yellow with black stripes.

That's crazy looking!

You got that right. This pest is not going to be confused with many other insects, although the Pennsylvania Department of Agriculture thinks that they look a little bit like the tiger moth (whose wings are shaped very differently) and the equally crazy-colored giant leopard moth, whose wings have none of the distinctive red of the lantern fly.

So—is this 'new pest in town' a true fly? Or a moth?

Neither—although it certainly looks like a moth, it's a plant hopper. It has usable wings, but it's more likely to jump around. And be aware that most of the ID pictures online have the wings spread out to show you the wild colors, but in reality those wings are often folded back when its hopping and feeding; and that's when you can tell it's a hopper and not a flyer.

So: How is it spreading? Hopping from town to town?

Yeah—like in an old Disney cartoon, carrying a little bag full of clothes up on a stick and singing 'The Lantern Fly Song'.

Actually, the way it spreads is really nefarious. After the adults finish feeding in the fall, the females lay 50 to a hundred eggs apiece on a solid object and cover the eggs with a substance that makes the nursery look like a patch of mud. These egg masses have been found on firewood, lawn furniture, cars and trucks. So, you load up for a camping trip in another state the following Spring….

…And you could have hitchhikers on the outside of the vehicle and in any stuff that was open to them outdoors…like that firewood.

We had a young woman on the show several years ago promoting a 'don't move firewood' initiative, and now I can see her point much more clearly. Nobody's going to scour over every piece of wood looking for patches of mud. So don't transport firewood. In addition, State Extension agents are urging people—including children—to learn to identify the egg masses on surfaces. I actually got some of my information from a coloring book published by the PA Department of Agriculture!


Hey; I stayed inside the lines.

Anyway, if you see what you think is an egg mass, take pictures of it before you destroy it and send the pictures to the researchers who are keeping track of this pest. We'll provide the links at the end of this Question of the Week.

And if you see adults?

It's a sight you won't soon forget. I was down the shore this summer and got calls from two friends who had stumbled upon infested trees. They both described hundreds, maybe thousands, of the things covering each of the trees. As expected, they were on the so-called "Tree of Heaven", an invasive—also from Asia—that's their primary host plant. But they will attack other trees—and grapes, apples and peaches.

What did you tell your friends to do?

Spray horticultural oil to keep the hoppers from hopping away, cut the trees down and burn them. For small infestations, sprays of horticultural oil alone should do the job.

These pests do have natural enemies back in Asia that are being actively researched. But right now, the best advice is to cut down most of the "Trees of Heaven" on your property, but leave a few standing as what's called a 'trap crop'. Check them regularly beginning in July and destroy any infestations you find—and check those trees for egg masses over the winter.


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