Prove your humanity

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Spotted lanternflies aren’t as harmful to most Pennsylvania hardwood trees as previously feared, according to new Penn State research. This study is the first of its kind to look at the long-term impacts of spotted lanternflies feeding on Northeastern hardwood trees.

Researchers in the study, published in the journal Environmental Entomology, put the invasive insect in enclosures with different types of trees to see how their growth would be affected. The trees included silver maple, weeping willow, river birch and tree-of-heaven.

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Kelli Hoover is an entomology professor at Penn State and the study’s lead author. She said none of the trees died during the four-year study.

Spottel lanternflies on a tree trunk

Spotted lanternfly. Spotted lanternflies on a tree trunk. Photo: PA Dept of Agriculture

“And in addition to that, this was the worst case scenario. You would never see lanternflies on trees this long. So in the real world, we’re not likely to see big reductions in growth, because the lanternflies – they’re just not on the trees that long,” Hoover said.

Adult spotted lanternflies cover this maple tree.

Adult spotted lanternflies cover this maple tree. Photo: Brian Walsh

The trees did have slower trunk diameter growth during the first two years of the study, but most recovered in the third year when researchers took away some lanternflies. The growth of the non-native tree-of-heaven, which lanternflies particularly like, remained flat in the third year.

“If you have a vineyard and you have lanternflies on your grape vines, you should be very worried because they can kill grape vines,” Hoover said. “But if you’re a homeowner and you have large trees on your property and you have lanternflies on them, I don’t think you should worry about it.”

Hoover does not believe it is worth it to spray insecticide on established trees to prevent spotted lanternflies.

“Because I don’t want to have side effects of killing natural enemies and pollinators, which is a risk. It’s a risk that you take,” Hoover said.

However, for anyone with a production nursery, Hoover said it is worth it to spray insecticide so it does not take longer to grow and sell the trees.

Hoover said, in addition to grapes, spotted lanternflies are especially harmful to hops, kiwi and cucumber plants. But she said Pennsylvania’s forests appear to be safe from spotted lanternflies.