Spotted lanternflies damage young maple trees •

A new study led by Pennsylvania State University has found that short-term, heavy feeding of adult spotted lanternflies on young maple trees inhibits photosynthesis and can stun tree growth by up to 50 percent. These results could help nurseries and forest managers make better decisions to protect these tree species.

“The spotted lanternfly feeds on important ornamental and woodland trees, such as silver and red maples, which are used to manufacture products and are abundant in urban, suburban and rural landscapes throughout Pennsylvania,” said study senior author Kelli Hoover , Professor of Entomology at Penn State.

This Asian lanternfly species was first discovered in 2014 in Berks County in the United States and has since spread to 45 counties in Pennsylvania and a few surrounding states. The pest uses its stinging, sucking maw to feed on the sap of over 100 plant species, with a strong preference for the tree of heaven (which is also an invasive species) and wild and cultivated grapes.

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

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

“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 different strategies to defend themselves; They can shift rates of photosynthesis and change the allocation of carbon and nitrogen resources to growth or induced plant defense.”

Analysis revealed that adult spotted lanternflies thwarted photosynthesis and reduced nitrogen concentrations in the leaves, thereby stunting tree growth, while nymphs had less of an impact on tree development. These decreases in tree growth were proportional to insect density.

“The bottom line is: the older the insects, the more harmful they are. If the spotted lanternfly feeds on your rose bush, particularly the nymphs, or if they’re confined to the underside of the leaves on your maple trees, they probably won’t do much damage. However, if they cover young trees, treatment with biopesticides or insecticides may be necessary,” Hoover concluded.

The study is published in the journal Frontiers in insect science.

Through Andrei Ionescu, staff writer

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