Benjamin Smith

Hemlock woolly adelgid is an invasive insect pest that has decimated hemlock forests and hemlock nursery production. This project will improve sustainable hemlock pest management and conservation by developing integrated pest management practices for hemlock production in nurseries to include least toxic insecticides and resistant hemlock genotypes. Hemlocks grown with these practices will protect the environment and will not harm biological control organisms released by state and federal agencies for hemlock conservation in forests.

This project will be a collaboration between the Forest Biotechnology Group in the Department of Forestry and Environmental Resources and the Forest Restoration Alliance in the Department of Entomology and Plant Pathology at North Carolina State University. We propose a integrative approach to understanding the genetic response to hemlock woolly adelgid (HWA) infestation in susceptible and resistant hemlock species, and how these genetic regulations are transduced to alterations in phenotypic traits associated with HWA susceptibility. The proposed project builds upon ongoing research in developing a CRISPR genome editing system for hemlocks funded by the SCBGP in 2020-21. Comparative transcriptomics and phenomics of hemlock variants with varying extent of HWA susceptibility will produce genetic insights that facilitate identification of candidate gene targets for editing using CRISPR-Cas to enhance HWA resistance. This project will focus on four key objectives: (1) controlled HWA infestation in putatively susceptible and resistant genotypes of hemlock species, (2) assessment of phenotypic response to infestation in hemlocks, (3) full transcriptomic analysis of hemlock response to HWA infestation, and (4) integration of transcriptomic and phenotypic responses to identify putative gene targets associated with HWA resistance. The putative genes identified in this project will be targeted for hemlock genome editing in a subsequent research that is beyond the scope of this project period.

This is an agreement to collect and sort white pine seeds for Woodland Restoration, Inc.

The specific issue that this project will address is the loss of a $10-$15 million annual farm income to the North Carolina nurseries and landscape industry, and the loss of native hemlock stands as a result of the introduction of an invasive pest, the hemlock woolly adelgid (HWA), into western North Carolina. Hemlock as a popular ornamental tree for landscaping has been virtually eliminated by HWA, destroying both in and out-of-state markets for NC nurseries. In addition, thousands of acres of natural hemlock stands in NC and throughout the ranges of eastern and Carolina hemlock have been devastated by HWA. This project will focus on locating native hemlock trees in natural stands with suspected levels of resistance to HWA, and initiating the multi-year process of propagating, either clones through rooting cuttings or half-sib families from collected open-pollinated seed, and subsequent phenotypic screening to select genotypes with genetic resistance to HWA.

��������������� Both the Forest Restoration Alliance (FRA) and Camcore of NC State University have experience in locating hemlocks that have survived the hemlock woolly adelgid (HWA). The location of the original trees is recorded and the trees are available for seed collection. ��������������� Searching for surviving hemlocks will continue in North Carolina and Kentucky utilizing Citizen Scientists, Forest Service personnel and the app Treesnap. ��������������� Seed will be collected by NC Forest Service personnel, and the collected seed will be planted in the greenhouses of the NC Forest Service nursery in Linville, NC. The resulting hemlock seedlings (offspring of survivors) will be available for reforestation. ��������������� A subset of hemlock seedlings will be tested for resistance/tolerance at the FRA facilities at the Mountain Research Station, Waynesville, NC. ��������������� At the appropriate age hemlocks will be planted on a variety of sites in NC and KY utilizing various silvicultural approaches. Volunteer Citizen Scientists could be involved in the planting. ��������������� The hemlocks will be followed through time to determine success of individual trees that may or may not show promise for resistance/tolerance, and to determine success of various silvicultural techniques. Again Citizen Scientists could be involved with this work.

The Forest Restoration Alliance of NC State University and its partners are beginning the process of reintroducing hemlocks to the landscape industry of western NC and restoring native hemlock stands lost to the hemlock woolly adelgid (HWA). The project will continue searching for surviving hemlocks by training field personnel, such as those with the NC Forest Service, and citizen scientists with the use of a new phone app TreeSnap. Seed and cuttings will be collected from the surviving hemlocks that are reported. A portion of the seed collected will be distributed to private nurseries for germination and seedling production for the ornamental industry. A portion of the seed will be provided to the NC Forest Service Linville nursery for germination and seedling production for reforestation in areas devastated by HWA. Short-term growth and survival of hemlock seedlings and rooted cuttings from surviving hemlocks exposed to HWA will be evaluated as a measure of short-term tolerance or resistance to the insect. A long-term silvicultural study to determine the appropriate techniques for best hemlock survival in ornamental and field plantings will be initiated. A long-term evaluation of all out-planted hemlocks to determine their growth, survival and infestation rates as measures of resistance/tolerance to HWA will begin.

��������������� Concerted push to find native resistance, including hiring two technicians dedicated to pursuing leads and propagating trees for screening, and utilization of the newly developed TreeSnap app. ��������������� Begin assembling HWA resistance screening study for as many commercially available hemlock cultivars as possible. ��������������� Distribute limited number of early selections of hemlock to several nurseries for long-term observation in ornamental landscape environment ��������������� Collect from new and recent sources of exotic hemlock pollen for interspecific hybrid crosses ��������������� Perform controlled pollinations to produce additional interspecific hemlock hybrids ��������������� Secure permission from US National Arboretum to utilize USNA-produced hybrid hemlocks for breeding, and begin pollen collections and controlled pollinations at NCDA Upper Mountain Research Station hybrid hemlock planting. ��������������� Begin testing techniques to stimulate pollen and cone production (floral induction) in exotic hemlocks planted at Mountain Horticultural Crops Research and Extension Center in collaboration with NCSU Horticulture faculty ��������������� Verify interspecific hybrids produced through somatic embryogenesis and conventional seed in collaboration with US Forest Service Forest Genetics Lab. ��������������� Continue to maintain population of healthy HWA at Mountain Research Station to infest screening trials ��������������� Collaborate with US Forest Service to begin process of screening for host resistance at additional sites in the eastern US.