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.
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