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Spotted lanternflies damage young maple trees

A new study led by Pennsylvania State University has found that short-term, heavy feeding by adult spotted lanternflies on young maple trees inhibits photosynthesis, and thus may impair the trees’ growth by up to 50 percent. These findings could help production nurseries and forest managers make better decisions on how to protect these types of trees.

“Spotted lanternfly will feed on important ornamental and forest trees such as silver and red maple, which are used to make products and are abundant across urban, suburban, and rural landscapes throughout Pennsylvania,” said study senior author Kelli Hoover, a professor of Entomology at Penn State.

This species of lanternfly, which originated in Asia, was first discovered in 2014 in the U.S. in Berks County and, since then, has spread to 45 Pennsylvania counties, as well as a few surrounding states. The pest uses its piercing-sucking mouth to feed on sap from over 100 plant species, with a strong preference for tree-of-heaven (which is also an invasive species), as well as both wild and cultivated grapes.

“While the spotted lanternfly likely co-evolved with its preferred host, tree-of-heaven, in its native range, the effects on the health and physiology of tree hosts native to the U.S. have not been investigated,” Hoover explained.

The scientists collected spotted lanternflies at two ages – adults and fourth instar nymphs (the last developmental stage before adulthood) – and placed them in different “densities” (number of insects per plant) on silver maple, red maple, tree-of-heaven, and black walnut saplings. Over a period of two years, they examined how insect density by life stage influenced physiological plant responses, such as photosynthesis.

“This process produces the nonstructural carbohydrates that trees need to grow and produce flowers or fruit,” Hoover said. “When plants are under stress, they use a variety of strategies to defend themselves; they may shift rates of photosynthesis and alter the allocation of carbon and nitrogen resources to growth or induced plant defenses.”

The analysis revealed that adult spotted lanternflies thwarted photosynthesis and reduced nitrogen concentrations in leaves, thus stunting the growth of the trees, while nymphs had less impact on tree development. These declines in tree growth were proportional to the density of the insects.

“The bottom line is that the older the insects, the more damaging they are. If spotted lanternfly is feeding on your rosebush, especially the nymphs, or if they are confined to the underside of the leaves of your maple trees, they’re probably not going to do much harm. But, when they are blanketing young trees, treatment with biopesticides or insecticides might be needed,” Hoover concluded.

The study is published in the journal Frontiers in Insect Science.

By Andrei Ionescu, Staff Writer

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