Impacts of short-term feeding by spotted lanternfly (Lycorma delicatula) on ecophysiology of young hardwood trees in a common garden

Abstract

Spotted lanternfly (SLF; Lycorma delicatula White; Hemiptera: Fulgoridae) invaded the US from Asia and was first detected in 2014; currently, populations have established in 14 states primarily in the Northeast and Mid-Atlantic. It feeds voraciously on phloem sap from a broad range of host plants, with a preference for tree of heaven (Ailanthus altissima [Sapindales: Simaroubaceae]), grapevines (Vitis spp. [Vitales: Vitaceae]), and several common hardwood tree species. We evaluated the impacts of fourth instars and adults confined to a single branch or whole trees on gas exchange attributes (carbon assimilation [photosynthetic rate], transpiration and stomatal conductance), selected nutrients, and diameter growth using young saplings of four host tree species planted in a common garden. In general, the effects of adults on trees were greater than nymphs, although there was variation depending on tree species, pest density, and time post-infestation. Nymphs on a single branch of red maple (Acer rubrum [Sapindales: Sapindaceae]), or silver maple (Acer saccharinum [Sapindales: Sapindaceae]) at three densities (0, 15, or 30) had no significant effects on gas exchange. In contrast, 40 adults confined to a single branch of red or silver maple rapidly suppressed gas exchange and reduced nitrogen concentration in leaves; soluble sugars in branch wood were reduced in the fall for silver maple and in the following spring for red maple. Fourth instars confined to whole silver maple trees reduced soluble sugars in leaves and branch wood, and reduced tree diameter growth by >50% during the next growing season. In contrast, fourth instars in whole tree enclosures had no effects on black walnut (Juglans nigra [Fagales: Juglandaceae]). SLF enclosed on tree of heaven at 80 adults per tree suppressed gas exchange after two weeks of feeding, but did not alter non-structural carbohydrates, nitrogen concentrations, or tree growth. Results suggest that moderate to heavy feeding by SLF on young maple saplings may impair tree growth, which could have implications for production nurseries and forest managers.

Keywords: black walnut; feeding damage; photosynthesis; red maple; tree physiology.

Figure 1

C assimilation over time measured on leaves in sleeve cages at the common garden in 2019. SLF adult densities were 0 or 40 per sleeve cage. Measurements were made on Sept. 24 and 27, and Oct. 1 and 4, 2019. Asterisks denote dates when rates on treated trees were significantly different from controls (p < 0.05).

Figure 2

Stomatal conductance of silver maple and red maple by SLF treatment measured on leaves in sleeve cages at the common garden in 2019 on Sept. 24 and 27, and Oct. 1 and 4. Spotted lanternfly adult densities were 0 or 40 per sleeve cage. Asterisks above the standard error bars denote dates when conductance on treatment trees were significantly different from controls (p < 0.05).

Figure 3

Transpiration measured in sleeve cages at the common garden in 2019 on Sept. 24 and 27, and Oct. 1 and 4 in response to 40 SLF adults per cage compared to controls. Asterisks above the standard error bars denote dates when transpiration rates on treatment trees were significantly different from controls (p < 0.1).

Figure 4

Carbon assimilation (photosynthetic rate) over time for tree of heaven (A) and silver maple (B) at the common garden. Spotted lanternfly adult densities were 0, 40, 80, and 120 per whole-tree enclosure. Note the differences in photosynthesis rates on the y-axes. Asterisks above the standard error bars denote dates when C assimilation rates on treatment trees were significantly different from controls (p < 0.05).

Figure 5

Average (least square means) concentrations of soluble sugars in branch woody tissue of silver (A) and red maple (B) trees exposed to SLF adults in sleeve cages. Branches were collected on October 4, 2019 (fall sampling), and March 27, 2020 (spring sampling). Carbohydrate concentrations are given in mg of glucose equivalents per g of dry tissue. Significant differences (p < 0.05) in soluble sugar concentrations between treatments for a given tree species within a sampling season are shown as different letters above the standard error bars.

Figure 6

Average (least square means) concentrations of soluble sugars in leaf and branch tissue of silver maple exposed to varying densities of fourth instar SLF nymphs during the whole-tree enclosures experiment. Leaves were collected on July 22 and 31, 2020, and branches were collected on July 31, 2020. Carbohydrate concentrations are given in mg of glucose equivalents per gram of dry tissue weight. Significant differences (p < 0.05) in fraction of soluble sugars for leaves and in soluble sugar concentrations for branches between treatments within a tissue type are shown as different letters above the standard error bars; standard errors are for each mean total non-structural carbohydrate concentration.

Figure 7

Mean tree diameter growth (at breast height) for silver maple during the growing season following the 2020 experiment as affected by SLF fourth instars feeding at different densities. Significant differences (p < 0.05) between treatments shown as different letters above the error bars. Tree diameters were measured on April 7, 2021 and March 15, 2022.

Figure 8

Mean percentage mortality per day for fourth instars in 2020 was influenced by SLF density in whole tree enclosures. Significant differences (p < 0.05) between treatments shown as different letters above the standard error bars.