Sara Villani

Ambrosia beetles, especially those belonging to the tribe Xyleborini, are recognized as extremely successful invaders worldwide. Two species of ambrosia beetles are especially problematic in nurseries and orchards, namely, the granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky) and the black stem borer, Xylosandrus germanus (Blandford). In the U.S., X. germanus tends to be more abundant and problematic in Midwest and the Northeast, while X. crassiusculus dominates the mid-Atlantic and the South. Unlike other wood-boring insects, ambrosia beetles tunnel into host trees to create galleries for rearing offspring and cultivating fungal symbionts serving as the sole source of nutrition for adults and larva. Physiological stressors predispose trees to attack by X. crassiusculus and X. germanus. Ethanol is emitted from stressed trees, and represents an important volatile cue used by ambrosia beetles to locate vulnerable hosts. Infestations of ambrosia beetles can result in branch dieback and tree death. Apart from direct losses of trees from beetle attacks, infestations can render trees unmarketable, increase pest management inputs, decrease integrity of surviving trees and make them vulnerable to secondary infection, and cause rapid decline in apple trees.

The United States (U.S.) is the second largest producer of pome fruit [apples (Malus x domestica) and pears (Pyrus communis)] globally. Producing 11 billion pounds of apples and 1.5 billion pounds of pears (NASS 2018), the US apple and pear crop is estimated at more than $4 billion (NASS 2017) with more than $7.5 billion in economic impact. With more than 18,815 apple and 10,246 pear farms nationally (NASS 2012) and 39,340 direct jobs (orchard to packing) in Washington alone, the apple and pear industry is an important contributor to jobs as well as the economy. Fire blight is the most devastating disease of pome fruit, and other fruit and ornamental plants of the Rosaceae family, and causes significant economic losses nationally. The actual costs incurred by growers and nurseries from fire blight losses and management efforts is difficult to estimate, due to costs of multiple sprays, tree losses, labor for pruning, removal of infected branches, fruit loss due to decreased quality, and the multi-year impact of lost tree productivity. In the U.S., fire blight is estimated to cause losses exceeding $100 million annually through blossom, shoot, and rootstock blight phase of the disease. In 2000, an epidemic of fire blight in Michigan led to loss of more than 600 acres of orchards (about 20% of the acreage in the region), and resulted in the death of 400,000 trees and over $50 million in economic losses to growers. The 2018 fire blight outbreak in Washington State caused an estimated 5% loss of total production of apple and pear, which translates to a loss of more than $100 million. Results of an online survey we conducted in Fall 2018 revealed that approximately 25% of 200 grower respondents had suffered significant fire blight infections in the last five years, leading to removal of more than 1,000 trees/per farm. Additionally, 23% of respondents estimated annual losses to fire blight at ~$4,000/acre and 46% of respondents lost ~$1,000/acre. Increased replanting costs of high-density blocks and losses of market accessibility due to stringent quarantine and international trade regulations associated with fire blight have resulted in financial costs and lost opportunities for many apple and pear growers. Our goal is to develop the following products through this project:1) Develop novel prescriptive approaches for blossom and shoot blight that increase precision in fire blight management; 2)Determine the impact of E. amylovora strain virulence on systemicmovement within trees, and develop detection methods for virulence typing to guide management decisions; 3)Develop apple pre-breeding lines with improved fire blight resistance and fruit quality traits using rapid cycle marker-assisted selection; 4)To develop bioeconomic models to identify profit maximizing and risk minimizing fire blight management strategies; and 5) To develop and deliver extension programming incorporating researchbased information to improve orchardist knowledge and application of effective fire blight management strategies.

Valued at over $85 million, North Carolina (NC) is ranked second in the United States for Christmas tree production. Fraser fir, grown predominantly in the western region, represents approximately 98% of cultivated Christmas tree cultivars grown in NC. Phytophthora root rot (PRR), primarily caused by the soil-borne pathogen Phytophthora cinnamomi, is the most economically devastating disease of Fraser fir in NC with disease incidence exceeding 50% in many commercial operations. The NC State University Woody Ornamental Pathology Program, in collaboration with NC Cooperative Extension and the NC Department of Agriculture (NCDA), will conduct basic and applied research to evaluate soil amendments for the suppression of PRR and reduce tree morality. The potential of gypsum and sulfur, incorporated alone or in integrated programs with wood mulches and phosphorous acid fungicides, will be evaluated in soil infested with and without Phytophthora spp. for its effect on seedling health and disease suppression. In addition to tree and root growth measurements, physiological indicators of conifer health including stomatal conductance, transpiration, and mid-day stem water potential will be measured. The incidence of infection by Phytophthora spp. will be determined for aboveground symptoms and root colonization will be quantified. To gain insight into the effects of soil amendments on microbial populations in the soil and roots, rhizosphere microbiome analysis of selected treatments will be conducted. A robust outreach program to inform stakeholders of project progress and results will be undertaken using a diversity of communication mediums including field days, grower meetings, and NCSU extension blogs.

Investigator will direct establishment and conduct of trial described in protocol. Investigator will direct collection and reporting of data as outlined in protocol and handle any disposition of trial materials necessary.

Rapid dieback (RD)of young apple trees is an emerging threat to the Eastern U.S. apple industry. RD involves the interaction of abiotic and biotic factors that cause the sudden collapse of young (��������������� 6 years), visually healthy trees on dwarfing rootstocks in tall spindle high-density planting systems. Symptoms of RD often mimic those of root system or rootstock disorders or diseases. RD has now been reported in apple producing states throughout the Southeast, Mid-Atlantic, and New England, as well as in Ontario, Canada. Despite the involvement of multiple cultivars, rootstocks, and climatic regions, the progression of decline from the graft union into the scion (trunk) has been a consistent symptom in nearly all instances of RD. Drought stress and infestation by ambrosia beetles and the colonization of their symbiotic and auxiliary opportunistic fungal pathogens has frequently been associated with RAD in the eastern US. The elucidation of abiotic and biotic factors associated with ambrosia beetle related RD and their relationship to physiological indicators of tree health is imperative for the development and implementation of an RD integrated management program.

Blackberries are an emerging and economically important commodity in NC with approximately 600 acres of commercial blackberries that are managed by approximately 25 commercial growers. Primocane-fruiting blackberry cultivars are a relatively new cropping system in the US and are especially prone to inadequate lateral branching. Inadequate lateral branch development can have negative consequences on blackberry productivity and profitability, since yield is positively correlated with lateral branch number. Additionally, disease management programs for primocane-fruiting blackberry are limited. Growers have concerns regarding development of fungicide resistance with current management strategies. We seek to conduct a comprehensive evaluation of factors that enhance lateral branching and develop new disease management programs to reduce risk of fungicide resistance of primocane-fruiting blackberry.

Over the last two years, several die-back and sudden death incidences in muscadine and vinifera vineyards in North Carolina were linked to grape trunk disease (GTD), caused by wood borne fungal pathogens. In the years 2018 and 2019, the Plant Disease and Insect Clinic at NC State processed approx. 45 samples linked to GTD. Moreover, dieback symptoms were consistently observed in both vinifera/hybrid style wine grape vineyards and well as muscadine vineyards throughout the years. GTDs occur in all grape growing regions in the world, and if unattended, lead to a reduced lifespan of vineyards, increased costs of production and to less favorable berry parameters. A variety of fungal pathogens are related to GTD, with physical damages to the trunk or cordon facilitate infection. In North Carolina particularly, we assume that cold damage and open pruning wounds are the number one entry points. Initial isolations from symptomatic vineyards in 2019 have shown that mostly pathogens of the large group of Botryosphaeria are present in North Carolina (Cline, Hoffmann, Villani pers. comm.). The danger of GTD is the long latency before the plant shows symptoms. Often first infections occur many years before a vine becomes symptomatic. However, dying plants can have a detrimental effect on vineyard productivity and therefore on the economic value of a vineyard. If unattended, vineyard productivity can decrease up to 80% over a span of 3-5 years. While management methods are well established in other grape growing regions and part of a vineyard management routine, in North Carolina (and in the Southeast for that matter), GTD management is not addressed, due to missing knowledge about GTDs aming farmers, but also due to several research questions on how to manage GTDs under the high rainfall conditions in North Carolina. Here we propose (1) to investigate the severity and incidence of GTD in North Carolina (2) to investigate the management of GTD in vinifera and muscadine grapes, using an integrated approach of cultural methods, physical barriers and chemical controls and (3) investigate risk assessments of GTDs. (4) Develop comprehensive outreach and extension program on the management and prevention of GTDs in vineyards in NC.

Investigator will direct establishment and conduct of trial described in protocol that was provided directly to the investigator and which will be uploaded to NCSU sponsored programs database in the Technical Description category of the PINS system if shared to College Research Office. Investigator will direct collection and reporting of data as outlined in protocol and handle any disposition of trial materials necessary.

Rapid Apple Decline (RAD), an emerging threat to the eastern United States apple industry, involves the interaction of biotic and abiotic factors that cause the sudden collapse of young dwarfing trees in high-density (HD) production systems. Surveys conducted by NC Apple Specialists in 2017 indicated that 80% of HD orchards in Western NC had trees with RAD symptoms, and often >30% of trees within orchards were affected. Drought stress and infestation by ambrosia beetles and the colonization of their symbiotic and auxiliary opportunistic fungi was regularly associated with RAD. Due to the cryptic life history of ambrosia beetles and opportunistic fungal pathogens, the challenges of identifying host physiological health status, and the limited efficacy of insecticides in controlling beetles, exclusive reliance on insecticidal control of ambrosia beetles is not a viable management option. Research from this proposal will contribute to the development of recommendations for RAD prevention and management that incorporate the contribution of ambrosia beetles, opportunistic phytopathogens, and quantifiable indicators of tree health status.

Objective: To compare the effects of sod and reflective groundcovers on canopy microclimate, bud phenology, yield, fruit quality, SWD infestation, disease incidence, and vegetative growth of ���������������Osage������������������ and ���������������Prime-Ark Traveler������������������ blackberry.