Robert Jetton

During the mid 1950s, nearly 70% of mature Fraser fir in natural stands was lost due to impacts of the invasive insect balsam woolly adelgid. Since the 1980s, there has been substantial regeneration and recovery in most Fraser fir stands across its native range. Recently, a new wave of mortality has been noted in several of these stands. The purpose of the proposed research is to document the extent of new Fraser fir mortality across its range, determine what age cohort (mature versus regenerated) is being affected, and identify potential factors underlying the observed mortality.

Although numerous studies have reported Eastern hemlock trees that have survived and remained healthy in areas that suffered high mortality rates due to HWA, no one has demonstrated that resistance to the adelgid is a genetically heritable trait passed down from parents to progeny. We propose to generate the appropriate genetic resources necessary for genetic studies through 1) vegetative propagation (grafting and rooted cuttings) of field selected hemlock trees in PA that have remained healthy in areas long-infested with HWA where most other trees are dead or declining and 2) generation of half-sibling seedling families using seed collected from these healthy trees (OP seed collections will also be submitted to the National Tree Seed Laboratory for long-term conservation) and 3) development of methods to induce early flowering in clonal propagules of healthy surviving hemlocks to generate full-sibling seedling families through controlled cross pollinations.

The purpose of this project is to fully develop, evaluate, and deliver an integrated management strategy for conserving and restoring eastern hemlock, an ecologically ���keystone��� species in eastern North America. The strategy will simultaneously utilize multiple tools (i.e., silvicultural, biological, and chemical tactics) to minimize negative impacts of the invasive hemlock woolly adelgid (HWA). Significant strides have been made in the application of these tactics individually or in paired use, but forest managers have consistently voiced the need for a cohesive strategy that applies multiple tools in the same ecosystem for combined benefit. Our studies will evaluate the interactive effects of silvicultural canopy gaps (that release groups of hemlock trees) and targeted chemical insecticide use (systemic neonicotinoids) on hemlock resilience and on pest and predator abundance The geographic scope of the project includes select sites in the northern and southern Appalachians, but results are expected to be applicable throughout the range of eastern hemlock.

The Hemlock Woolly Adelgid is a destructive invasive insect pest of hemlock forests in the Southern Appalachian Mountains. Beneficial bacterial endosymbionts of the adelgid play key roles in the insect's biology, including the digestion of nutrients, defense against natural enemies, and resilience to environmental stress. The PI and his US Forest Service collaborators have recently demonstrated that silvicultural release of infested hemlock trees to increase light exposure and resource availability can make trees more resilient to adelgid infestation. Processes underlying why release is beneficial to the tree are not fully understood, but it is hypothesized that both behavioral responses to sunlight and physiological effects of increased temperatures on the part of the adelgid are involved. The study proposed here will explore the interactions of the adelgid and endosymbionts associated with heat stress across of set of previously established silvicultural release plots to better understand the mechanisms underlying the success of silvicultural release on hemlock health.

This agreement supports a cooperative project between North Carolina State University and the USDA Forest Service Southern Region for the genetic resource conservation of threatened and endangered tree species in the Southern Region, on the Southern Appalachian forests. Genetic diversity studies are critical in understanding adaptation of imperiled tree species to climate change and forest health impacts. This agreement will allow NCSU, Camcore to identify and add new imperiled tree species to the list for new seed collections. Genetic diversity studies will be done on the species and seeds will be used in restoration efforts on the Southern National Forests.

Previous and ongoing research shows that cutting gaps around individual or small groups of hemlock woolly adelgid (HWA) infested eastern hemlocks to increase the level of sunlight exposure to the crown reduces HWA densities and improves the growth and carbon balance of the tree. How to apply and combine such release strategies with other HWA management tools remains unclear. This project will develop and validate silvicultural thinning tool that will be integrated with existing HWA chemical and biological control strategies to improve the health and long-term sustainability of eastern hemlock in the southern Appalachians.

A monitoring program for Carolina hemlock ecosystems will be implemented across the species range. Vulnerability will be assessed using long-term growth, climate, and insect infestation patterns. Growth and mortality rates from the spatially extensive empirical data will be tested against Carolina hemlock status conditions from the Forest Inventory and Analysis program data.

In collaboration with scientists at North Carolina State University and USDA ARS, scientists at Washington State University will utilize detached branches to determine the potential effectiveness of postharvest fumigation treatments with Bluefume (HCN) in killing elongated hemlock scale (EHS) life stages on infested Fraser fir and determine the effects of HCN fumigation on the postharvest quality of non-infested commonly-grown Christmas tree species,such as balsam fir, Canaan fir, Fraser fir, grand fir, noble fir, Nordmann fir, Turkish fir, Trojan fir, and Douglas-fir). Branches will be fumigated at the USDA ARS Postharvest facility in CA. Treatments will consist of 5 rates of HCN plus a non-fumigated control. Each treatment will be replicated 3 times with 3 branches per replication. Following fumigation, the viability of EHS life stages on infested branches will be assessed. Uninfested branches from the commonly grown species will be transported and displayed in a temperature-controlled room to determine if the fumigation treatments have any adverse effects on postharvest quality and needle retention.

In collaboration with scientists at North Carolina State University and USDA ARS, scientists at Washington State University will utilize detached branches to determine the potential effectiveness of postharvest fumigation treatments with Bluefume (HCN) in killing elongated hemlock scale (EHS) life stages on infested Fraser fir and determine the effects of HCN fumigation on the postharvest quality of non-infested commonly-grown Christmas tree species,such as balsam fir, Canaan fir, Fraser fir, grand fir, noble fir, Nordmann fir, Turkish fir, Trojan fir, and Douglas-fir). Branches will be fumigated at the USDA ARS Postharvest facility in CA. Treatments will consist of 5 rates of HCN plus a non-fumigated control. Each treatment will be replicated 3 times with 3 branches per replication. Following fumigation, the viability of EHS life stages on infested branches will be assessed. Uninfested branches from the commonly grown species will be transported and displayed in a temperature-controlled room to determine if the fumigation treatments have any adverse effects on postharvest quality and needle retention.

This project will be a collaboration between the Christmas Tree Genetics Program, the Forest Health and Conservation Program, and the Molecular Tree Breeding Lab in the Department of Forestry and Environmental Resources at North Carolina State University. Our goal is to accelerate the genetic improvement of Fraser fir against the tree-killing pathogen Phytophthora root rot and insect pest balsam woolly adelgid. Fraser fir is one of North Carolina������������������s most important specialty crops generating annual revenues exceeding $100 million. The development of novel genomic tools and technologies will have a positive, transformative impact on the North Carolina Christmas tree industry. Our project builds on resources developed by the NCSU Christmas Tree Genetics Program in collaboration with the NCDA and NC Christmas tree growers over the past 4+ decades. We propose five major objectives in this proposal: (1) genomic resource development of Fraser fir responses to Phytophthora and BWA; (2) identification of Phytophthora and BWA elicitors; (3) evaluation of Fraser fir responses to isolated elicitors; (4) population level analysis of key pest responsive genes in existing NCSU Fraser fir breeding program resources; and (5) synthesis and dissemination of results to NC Christmas tree stakeholders. Subsequent to the funding period, these efforts will benefit the North Carolina Christmas tree community and contribute to the genetic conservation of native Fraser fir populations in the Appalachian Mountains. We expect project deliverables will help address key knowledge gaps of pest resilience in Fraser fir and push conventional conifer breeding strategies and integration with genomic information into a new era.