Invasive Spotted Lantern Flies Settle in Rhode Island
By Mike Freeman / ecoRI News contributor
This year researchers confirmed the insect is breeding in Rhode Island. How
they got here is now an old, sad, oft-repeated tale.
Humans love stuff. We make it, buy it, steal it, sell it. We war
for it. Trade fairly defines us, and as transport has gone from baskets to
carts to sloops to planes and leviathan barges, our thirst hasn’t abated. The
upshot is more stuff — fast and cheap. The downside is a biospherical goat
rope.
Ecosystems evolve with specific interdependencies. Parachuting a
new pathogen or species in — as human trade often does — can be catastrophic.
Flora, fauna, viruses, fungi — all cross oceans via our trade. Some we bring
willingly, others stow away.
In New England, chestnut blight, Dutch elm
disease, green crabs, bittersweet vines, phragmites, and the emerald ash borer are
just a few that have refashioned local environments for the worse. Spotted
lantern flies (SLF) are the latest iteration, with yet-to-be-determined
consequences.
“We found the first adult in Warwick in 2021, and this year found them established in North Smithfield,” said the University of Rhode Island’s Lisa Tewksbury, who manages invasive plants and insects across the state. While she doesn’t believe SLF are as damaging as emerald ash borers — which came to Rhode Island in 2018 and threaten all ash species with extinction — Tewksbury by no means welcomes them.
“The adults prefer just a few trees,” she said. “Among them are
fruit trees and grape vines, so there could be economic damage in our orchards
and vineyards. The earlier life stages, or instars, aren’t very mobile though
and have been recorded feeding on over a hundred plants. This adds an
additional stressor. We had a bad drought this summer, so in situations like
that spotted lantern flies will cause further decline in already stressed
plants.”
As adults, SLF are striking. Black dots on pale white wings, two
swaths blotted in vermillion, they seem more art than life. That’s great in
their native Asian range, where plants evolved with them and have natural
defenses, but here, as with other invasives, native plants are vulnerable and
most endemic predators have yet to develop a taste. Unironically, SLF’s North
American table was set long before they arrived, as early Americans brought
their top host plant over from China in the late 1700s.
“It’s tree-of-heaven, or ailanthus tree,” Tewksbury said. “There
are other preferences like black walnut, but tree-of-heaven is the spotted
lantern flies’ top choice, which are common street and park trees around the
country.”
SLF, then, came to a happy home. It’s thought that they arrived
as spawn on a flagstone shipment offloaded in Pennsylvania, which isolates a
chief difficulty in trying to manage them.
“They lay eggs everywhere,” Tewksbury said. “Outdoor tables,
chairs, boats, everything. They’re also effective hitchhikers, traveling great
distances as eggs, instars, or adults in RVs, cars, and trucks.”
Precise predictions are impossible, but Rhode Island will likely
be fully colonized in a year or two. What that means remains murky, though with
other states providing an eight-year template, what to expect and what to do
are clearing up.
To date, tree-of-heaven and grape vines are the only plants to experience direct mortality from SLF. In all life stages the insects bore into plants to feed on sap. Since tree-of-heaven is itself an invasive, any mortality there will see towns suffer replacement costs, but the trees are creeping into native forests so won’t be missed environmentally.
Wine grapes and fruit trees are another matter. Pennsylvania vineyards have seen vines die, and apple orchards are another top SLF target, though for now the insects’ drilling isn’t thought to be lethal.
“We’re not too worried yet,” said Sharon Grenier, co-owner of
North Kingstown’s Narrow Lane Orchard. “People from the state have trapped for
them for years here. If they make their way down we’ll address it, but right
now it’s not a big concern.”
Tewksbury pointed to another worry. In short, SLF are gross. In late summer and early fall adults become highly social, crowding trees. Their excrement fosters growth called sooty mold, covering trees in black, stinky gunk.
The sweet sap also draws wasps, including yellowjackets. In a forest
setting none of this matters, but anyone who has dined outdoors from Labor Day
on knows yellowjackets aggressively forage tables. Sooty mold has worsened that
elsewhere, and Rhode Island’s many tree-of-heaven-lined streets will see the
same.
Mitigation is underway. The state is spraying North Smithfield
for SLF, and biocontrol researchers are seeking Asian parasitoid wasps that
only target SLF, such as has been done for the emerald ash borer. For now,
though, none have been approved for release.
Tewksbury said there’s only so much the state can do, and with
SLF so visible in the fall breeding season, public participation will help.
Checking outdoor furniture for the clay-like egg masses is a start, as is checking
cars for adults. Past that, smooshing is highly recommended. New York and
Philadelphia openly advocate stepping on adults, and while this isn’t for
everybody, there are alternatives.
“Squashing puts some people off,” Tewksbury said. “You can trap
them in water bottles where they’ll drown. However you kill them, that will
help slow their spread and limit their damage.”
If SLF aren’t as apocalyptic as other invasives like chestnut
blight or phragmites, they’re certainly the latest in a long lineage of environmental
threats generated by our thirst for stuff. That thirst won’t end, but we can
blunt the damage invasives cause while pressuring lawmakers to implement
stricter shipping regulations to prevent species both from arriving and
departing here.