ECOLOGICAL AND BIOLOGICAL INTERACTIONS BETWEEN SPOTTED LANTERNFLY AND HOST TREES IN THE LANDSCAPE

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1021211
• Project Start Date: Mar 7, 2020
• Project End Date: Sep 30, 2024
• Program Code: [(N/A)]- (N/A)

Project Director
Hoover, KE.

Recipient Organization
PENNSYLVANIA STATE UNIVERSITY
208 MUELLER LABORATORY
UNIVERSITY PARK,PA 16802

Performing Department
Entomology

Non Technical Summary
Spotted lanternfly (SLF) is an introduced, phoem-feeding invasive insect from Asia that threatens numerous specialty crops (including grapes, stone fruits, hops, and ornamentals) in PA and other parts of the Northeast and mid-Atlantic. Basic information is lacking on SLF biology and ecology, making containment and control difficult. We will fill knowledge gaps to determine which host plants can support development of each life stage of SLF and how far each instar can disperse in various landscapes. A critical issue is to determine definitively if SLF requires Ailanthus altissima to reproduce and, if not, if the absence of Ailanthus reduces SLF fitness. Knowledge of how SLF feeding afffects sugar metabolosm in A. altissima compared with other preferred host tree species may provide clues as to why this tree is preferred (or required) by this pest. Impacts of SLF on tree physiology at different levels of pest pressure will also contribute to our ability to predict at what densities it may have long-term effects on tree health. We will also develop sampling methods to estimate population abundance and distribution of SLF, which will facilitate directing and assessing the efficacy of control efforts. Currently, sampling methods can do little more than provide presence/absence information. Having methods to sample key life stages of SLF to estimate population abundance and dispersion is essential for eventual implementation of IPM programs and setting program goals for containment.

Animal Health Component

25%

Research Effort Categories

Basic

75%

Applied

25%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
124	0613	1060	50%
211	0620	1070	50%

Knowledge Area
211 - Insects, Mites, and Other Arthropods Affecting Plants; 124 - Urban Forestry;

Subject Of Investigation
0620 - Broadleaf forests of the North; 0613 - Mixed conifer-broadleaf forests;

Field Of Science
1060 - Biology (whole systems); 1070 - Ecology;

Keywords

hardwood trees

spotted lanternfly

host range

dispersal

population dynamics

Goals / Objectives
The goals of this project are to address basic ecological and biological questions about spotted lanternfly (SLF) host preferences and performance on different woody hosts, dispersal behaviors and distances, and population dynamics. This knowledge will be used to develop IPM strategies for management of SLF.1. Determine host tree preference and performance of SLF by life stage among common trees in the landscape and whether it must feed on Ailanthus to produce viable offspring.2. Examine the impacts of SLF feeding on the physiology and health of field grown trees.3. Evaluate how far each nymphal life stage can disperse in different landscapes.4. Develop sampling protocols for quantifying SLF abundance and dispersion in the landscape.

Project Methods
1a. Using large enclosures in the quarantine area we established 4 different tree species (1 each of silver maple, red maple, black walnut, and willow) and either 1 river birch (5 plots) or 1 Ailanthus tree (5 plots) in each plot. In May, we will release 300 1st instar nymphs into each enclosure. Over the season, the number of living nymphs on each tree species, the number of nymphs that molt to adult, longevity of adults, and number of egg masses laid in each enclosure will be recorded. The following spring, the number of live nymphs that hatch and the number of unhatched eggs will be counted to calculate the proportion of viable nymphs by treatment to compare fitness with and without access to Ailanthus.1b. Another approach will be to use a common garden that was established in Berks County containing 4 tree species (red and silver maple, black walnut, and Ailanthus) in a randomized split plot design with 3 blocks, providing 9 replicates of each treatment per block. When SLF begin to hatch in the field, single tree enclosures will be placed over each experimental tree to confine first instar SLF at different densities with freedom to move among the annuals and the entire tree. Subplot treatments will consist of 4 different levels of pest pressure (0, light, moderate, and heavy density). At set intervals, we will count the number of living insects of each life stage on each tree species and record characteristics of tree health. The number of adults and the number of egg masses per tree will be recorded.2. To evaluate shifts in carbohydrate metabolism, we will sample 1-2 portions of stem from each tree in Obj. 1b to quantify non-structural carbohydrates, photosynthesis and stomatal conductance of two leaves per tree from 9 am to 1 pm under saturating light conditions (2000 µmol m-2 s-1) using a Li-6400. Sap flow meters will be set up as well on a subsample of trees at each density of pest pressure. We will determine the relationship between carbon assimilation (A) and internal CO2 concentration (ci) to assess the relative importance of stomatal conductance vs. mesophyll conductance on influencing carbon assimilations (i.e., A/ci curves).3. We will use mark/release/re-sight methods to quantify SLF dispersal into differing habitat types from a central release point located at the interface between two habitats. We have conducted an extensive pilot study marking SLF nymphs of each instar with neon dayglo powder and re-sighted them after release using UV flashlights and handheld lasers in nighttime searches. In the proposed study, we will extend this project by studying dispersal at the interface between forested areas and cropland (vineyards and orchards), between disturbed areas with tree of heaven left intact and tree of heaven removed, and between forested and disturbed areas. We will set up a central release point and establish twelve 50 m radial transects from the release point. Every 5 m will be marked with fluorescent flags visible in the dark. At least 2000 nymphs of each life stage will be marked with Day Glow fluorescent powder, using a different color for each instar, and released in the center of the 50 m radius plot; release dates will be staggered according to which life stage is prevalent in the field at the time. The next day and every 3 days after, night searches will be done on each transect using UV flashlights and again using handheld lasers, which can spot nymphs 40 m up in a tree. Every other transect will include dropping a marker where marked insects are found, and the distance measured from the marked insect location to the closest transect line to allow us to calculate the probability of detection. Dispersal distances for all life stages and each transect will also be recorded.4. Egg masses are laid rather indiscriminately by SLF (including on metal posts and rocks), which is similar to gypsy moth, so we will use our knowledge about gypsy moth sampling by focusing first on the egg mass stage. Using fixed radius plots we will quantify the spatial distribution of egg masses among tree species and at different canopy strata as a function of SLF density. With these data, we can develop applied sampling protocols. Abundance will be determined by examining the proportion of eggs that hatch in a subsample of egg masses. We will also conduct counts of newly hatched nymphs on sticky bands wrapped around trees with egg masses and use ground traps to catch nymphs as they drop from trees shortly after hatching to ensure we capture most of the newly hatched nymphs. This will allow us to calibrate the relationship between nymph abundance and egg mass counts per area.We will explore sampling late (4th) instars and adults using "8x8 counts". This is a method that has previously been applied by us in which searching is conducted 8' up from the base of the tree, and 8' out on any branches. To calibrate this method, we will conduct 8x8 counts on several fixed radius plots and then treat all trees within plots with dinotefuran tree injection to knock-down nymphs. After 3 days we will count nymphs and adults falling on tarps placed below trees. We will then statistically model 8x8 counts, and sticky band counts to the number of SLF that drop from trees. We have developed a reliable linear regression model that calculates the number of dead spotted lanternflies dropped from trees based on dry weight.

Progress 03/07/20 to 09/30/20

Outputs
Target Audience:Audiences for this research include USDA and PDA, especially those handling SLF management, other researchers, and the general public. All information that was gathered in the past year has been conveyed to government agencies, other scientists that work on SLF, and to the general public through press releases and extension educators. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Both postdoctoral researchers and the graduate student on this project learned new skills in their first year studying SLF, including a great deal of practical information about this pest's biology, ecology and behavior. One of the postdocs and a graduate student wrote grant proposals during the past year and so far, twoout of threehave been funded (the third has not yet been reviewed). All personnel also gained training in public speaking, supervision of undergraduates, and time management. Field work during a short season with the insect having only one generation per year requires significant planning and prioritizing of tasks throughout the season. How have the results been disseminated to communities of interest?Three publications on our work on SLF over the past year were published or are in press. Results have also been conveyed at SLF Working Group Meetings, the Specialty Crop Research Initiative (SCRI) grant collaboration meetings, at Ecological Society of America meetings, at nursery, forestry and landscape industry meetings, and in press releases produced by PSU extension and the Communications Team. We have given talks about our findings and ongoing projects at several other venues as well for end users such as forest managers and the PA Department of AgricultureHardwoods Development Council. What do you plan to do during the next reporting period to accomplish the goals?Objectives 1 and 3 were completed. During the next reporting period for Objective2 we will evaluate shifts in carbohydrate metabolism.We sampled one-two portions of stem from each tree in all experiments described above to quantify non-structural carbohydrates. We are also currently processing these samples for analysis for carbohydrates and other samples for metabolomics to determine the species of sugar and changes in other nutrients or plant chemical defenses following SLF feeding pressure. We will repeat this study in 2021 adding impacts of SLF feeding on induced plant defenses and by adding additional hosts of SLF. For Objective4, ongoing satellite population monitoring will assess the year-to-year change in SLF densities at these sites, a number of which have Ailanthus that were treated with herbicide. Tracking the growth or decline of these populations will allow us to evaluate the success of management. Ongoing analysis of data shows that sampling methods do not always have similar sensitivity. Generally, visual search for nymphs and adults was the most sensitive sampling method, while both types of traps occasionally failed to capture any individuals at low-density sites. By the end of this study we should be able to inform regulatory agencies about 1) which trapping methods are more effective for nymphs vs. adults, especially when SLF populations are low and 2) which treatment methods are most effective at eradicating or minimizing spread of SLF populations at localized satellite populations.

Impacts
What was accomplished under these goals? Objective 1. We examined fitness effects of SLF reared from egg to adult in multi-tree enclosures. Nymphs had access to planted silver maple, willow and black walnut. Half of the tenenclosures had Ailanthus while the other half had river birch instead. Without Ailanthus, survival to adult was slightly lower and fewer egg masses were laid, but hatch rate the following spring did not differ between treatments. Although SLF can develop and reproduce without access to Ailanthus, fitness is reduced, which has management implications. Objective 2. For the trees in Objective1, we investigated the effects of SLF feeding on tree physiology. Leaf gas exchange was measured monthly in the multi-tree enclosures containing SLF nymphs and adults. River birch had the highest photosynthetic rate followed by Ailanthus, willow and silver maple. In river birch, increasing SLF pressure suppressed gas exchange, and at the highest level of pressure, photosynthesis was suppressed. In contrast, increasing SLF numbers enhanced gas exchange in willow by 50% at the highest pest density. Photosynthesis of silver maple and Ailanthus was unaffected. Water use efficiency was suppressed for all species with increasing SLF density. In July and August, we did not detect measurable effects of SLF feeding on gas exchange and water use efficiency. Controlled experiments were conducted at the common garden in Berks County where the year before we had planted 800 trees in a split plot completely randomized block design consisting of fourtree species: red and silver maple, black walnut and Ailanthus. In 2020 we investigated the effects of SLF feeding pressure on silver maple, Ailanthus and black walnut. Experimental and control trees (silver maple and black walnut) were fully enclosed with mesh and received fourthinstars at fourdifferent density levels (0-120) in July. In August, adults at the same densities were enclosed on silver maple and Ailanthus. Leaf gas exchange was measured every three-fourdays. For tendays of infestation, fourthinstars had no effect on leaf gas exchange of either silver maple or black walnut. In contrast, adult feeding gradually suppressed leaf gas exchange over time in silver maple and Ailanthus. At 20 days of adult feeding, photosynthesis of Ailanthus was suppressed by about 30%, 74% and 25% at light, moderate and heavy infestation levels compared to controls. For silver maple, moderate and heavy SLF infestation reduced photosynthesis, while light pressure had no effect. Transpiration for Ailanthus was suppressed for trees with moderate infestation, but trees with light and heavy infestations had similar transpiration rates to the control. For silver maple, transpiration was suppressed for trees with moderate and heavy infestation while transpiration for trees with light pressure was similar to the control. Water use efficiency by Ailanthus was not affected by SLF across treatments, while silver maple water use efficiency was 2X higher for trees with moderate infestation compared to the other treatments. Objective 3. We conducted a mark, release, re-sight study in contiguous forest by marking >2000 nymphs with fluorescent powders and observing dispersal distances from a central release point at threetime points over sevendays. We repeated this process for each of SLF's fourinstars. Nymphs were resighted using UV flashlights on a variety of trees, shrubs, and understory vegetation. Most nymphs remained near the release location, while some moved tens of meters. All fourinstars had similar dispersal distances over time, though thirdinstar nymphs moved farthest (65 m in sevendays). The median displacement from the release location was 6.2m, 13.4m, 16.9m, and 8.3m for first, second, thirdand fourthinstars, respectively. Objective 4. We established 14 study plots in and around the Shippensburg, PA outlier SLF population, fivein Huntingdon, and 33 in Altoona. At these sites, we repeatedly assessed SLF density, first by counting egg masses. Once nymphs hatched, we monitored populations every other week through the season using twosampling methods: visual counts (by two observers on each occasion) and installation of Bug Barrier sticky traps. Modified circle traps were installed once adults appeared in July. SLF were found at sixlocations previously thought to fall outside the boundaries of these small outlier populations. These finds were reported to the PA Dept. of Agriculture.

Publications

• Type: Journal Articles Status: Published Year Published: 2020 Citation: Keller, J.A., A.E. Johnson, O. Uyi, S. Wurzbacher, D. Long, and K. Hoover. 2020. Dispersal of Lycorma delicatula (Hemiptera: Fulgoridae) nymphs through contiguous, deciduous forest. Environ. Entomol., doi:10.1093/ee/nvaa089.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Uyi, Osariyekemwen, J. Keller, A. Johnson, D. Long, B. Walsh, and K. Hoover. 2020. Spotted lanternfly can complete development and oviposit without access to the preferred host, Ailanthus altissima. Environ. Entomol. DOI:10.1093/ee/nvaa083.
• Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Keller, J., J. Rost, K. Hoover, J. Urban, H. Leach, M. Porras, B. Walsh, M. Bosold, and D. D. Calvin. 2020. Dispersion pattern and sample size estimates for spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), egg masses. Environ. Entomol., in press.