Long-term feeding impacts of spotted lanternfly (Lycorma delicatula) on ecophysiology of common hardwood tree hosts

While the invasive spotted lanternfly (Lycorma delicatula) continues to expand its range in the U.S., there remains a knowledge gap regarding the economic threat that this pest presents to forest ecosystems and production nurseries. L. delicatula uses several common hardwood trees as hosts and a previous study found that short-term feeding can reduce growth of young maple saplings. Long-term feeding over four consecutive seasons significantly reduced diameter growth and below-ground starch storage in roots of young silver maples (Acer saccharinum), weeping willows (Salix babylonica), river birches (Betula nigra), and trees of heaven (Ailanthus altissima) in response to L. delicatula feeding pressure in a density-dependent manner. In Year 3 when feeding pressure was the lowest, silver maple and willow recovered with greater diameter growth than in Year 2. Nutrients essential for photosynthesis and growth (iron, sulfur, and phosphorus) were reduced in leaves of all tree species compared to controls in the second year. This four-year study represents a worst-case scenario in which L. delicatula fed on the same trees for four consecutive growing seasons. In the wild, population numbers can vary greatly from year to year on individual trees and they move frequently among hosts (until autumn when they settle on A. altissima or other late-season hosts that have not yet senesced). Thus, we would not expect negative impacts of unconfined L. delicatula in natural settings on forest or ornamental trees to be as marked as reported here.