When spotted lanternflies showed up in Pennsylvania nearly a decade ago, they brought with them huge fears about their impact on east coast flora and fauna. The invasive bug can now be found throughout Maryland.
But a new study out of Pennsylvania State University shows that important native east coast tree saplings, including those in Maryland, are proving resilient against the invader bug.
Scientists studied the effects of spotted lanternfly feeding on tree saplings of silver maple, weeping willow, river birch and tree-of-heaven. Almost all of them were able to make a comeback after lanternfly feeding was reduced, with one exception: the tree-of-heaven.
Like the spotted lanternfly, the tree-of-heaven is an invasive plant from China. “So who cares? In fact, that's a good thing!” said entomologist Kelli Hoover, a scientist with Penn State and leading author on the recent study.
Scientists focused on those species because they are some of the most common hardwoods sold in east coast commercial nurseries. Lanternflies also love them; they’ve become some of the most common hosts for the bugs out in nature.
The saplings suffered when a large number of lanternflies fed on them; trunks grew smaller and photosynthesis stalled. The trees weren’t able to store as much starch in their roots. But the next year, when scientists introduced fewer bugs, the trees thrived. They repeated the cycle and found the same result, saplings suffered but then recovered.
Hoover said that the damage done to the saplings when they are heavily harvested upon by the bugs is “significant.”
Brian Walsh, a horticulturist with the Penn State Extension campus who also worked on the study, explained that the study mimicked the lanternfly feeding cycle in nature.
“We tend to see a couple of years of heavy infestation and then sudden drop off. We can see significant rise in subsequent years, but the insects for whatever reason, the population seems to be… moving around and changing in densities,” said Walsh.
The study also set up a “worst case scenario.” Seeing as the tree saplings were still able to bounce back, Hoover is encouraged.
“None of the trees died. And remember, these are saplings. They're not very big trees,” said Hoover. “And the smaller the trees, the more sensitive they are to lantern fly feeding. We don't see lanternflies killing established trees in nature, except for the tree-of-heaven.”
An earlier study, also conducted with Hoover and Walsh, showed similar positive results for red maple and black walnut saplings.
“If you're a nursery… with trees you are trying to grow from small saplings into larger trees to sell. You definitely need to worry about treating those trees… It could slow down how quickly those trees are going to be saleable,” suggested Hoover.
But for regular homeowners, especially those with more mature trees, Hoover recommends passing on the treatments and insecticide. She said that likely offers more risk to other pollinators and family pets than there is risk of spotted lanternfly damage on those trees.
In all, the study offers a glimmer of hope: In the battle of tree versus spotted lanternfly, trees can win. Unfortunately, that may be where the good news ends. The insects still do undoubtable damage to hops and vineyards, said Hoover.
