@article{stephens_gannon_cubeta_kerns_2024, title={Influence of fungicide selection and application timing on take-all root rot management under field and greenhouse conditions}, volume={10}, ISSN={["2374-3832"]}, DOI={10.1002/cft2.20261}, abstractNote={Abstract Take‐all root rot is a detrimental disease of ultradwarf bermudagrass putting greens frequently diagnosed where warm‐season grasses are grown. Since this disease is largely aggregated and variable under field conditions, field research is difficult and often yields inconsistent results. Multiple pathogens have only recently been associated with this disease, so practical management solutions such as fungicide efficacy and fungicide application timing have not been thoroughly investigated. Therefore, the objectives of this research were to determine the influence of fungicide selection and fungicide application timing on take‐all root rot management under field and greenhouse conditions. In general, fungicides from the QoI and/or DMI chemical classes provided the greatest reduction in take‐all root rot severity. Fungicide applications that were made when soil temperatures were between 77–86°F provided the greatest disease suppression. The in vivo greenhouse method developed in this research proved to be an efficient and consistent method to evaluate management practices such as fungicide efficacy on take‐all root rot. This research improves our understanding of fungicide efficacy and fungicide application timing for take‐all root rot management on ultradwarf bermudagrass. This article is protected by copyright. All rights reserved Plain Language Summary: Take‐all root rot (TARR) is a detrimental disease on bermudagrass putting greens. It is difficult to study under field conditions, and fungicide application timing is not well studied. We developed a greenhouse method to test fungicide efficacy against TARR pathogen inoculated bermudagrass and evaluated fungicide application timing under field conditions to determine the best time to apply for TARR management. We were successfully able to produce TARR symptoms using our greenhouse method and determine fungicides from the QoI and DMI chemical families provided the greatest reduction of TARR. Applications made when soil temperatures were between 77–86°F provided the greatest disease suppression.}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Stephens, Cameron M. and Gannon, Travis W. and Cubeta, Marc A. and Kerns, James P.}, year={2024}, month={Jun} }
 @article{stephens_gannon_thiessen_cubeta_kerns_2023, title={In Vitro Fungicide Sensitivity and Effect of Organic Matter Concentration on Fungicide Bioavailability in Take-All Root Rot Pathogens Isolated from North Carolina}, volume={24}, ISSN={["1535-1025"]}, DOI={10.1094/PHP-08-22-0072-RS}, abstractNote={ Take-all root rot (TARR) of ultradwarf bermudagrass is caused by Gaeumannomyces graminis (Gg), Gaeumannomyces graminicola (Ggram), Candidacolonium cynodontis (Cc), and Magnaporthiopsis cynodontis (Mc). Multiple pathogens have recently been associated with this disease, and biological parameters such as fungicide sensitivity have not been explored in ultradwarf bermudagrass. Although fungicides are commonly used to mitigate disease development, high organic matter present in the turfgrass system could limit the bioavailability of fungicides. Fungicide bioavailability can be influenced by organic matter concentration, and the physicochemical properties of fungicides could provide insight into their binding affinity. However, the influence of organic matter content on fungicide bioavailability has not been investigated. Therefore, the in vitro sensitivity of Gg, Ggram, Cc, and Mc to 14 different fungicides across three chemical classes was determined. An in vitro bioavailability assay was developed using three fungicides and three organic matter concentrations. Generally, demethylation inhibitor and quinone outside inhibitor fungicides provided the greatest reduction in mycelial growth, whereas succinate dehydrogenase inhibitors did not reduce mycelial growth. These data can serve as a foundation for TARR pathogen sensitivity to inform in vitro fungicide sensitivity studies and field efficacy trials. Pyraclostrobin and propiconazole have a high affinity to bind to organic matter, which was evident as more fungicide was required to inhibit Gg growth as organic matter concentration increased. This was not observed when evaluating azoxystrobin, which has a lower binding affinity. Understanding how TARR pathogens respond to fungicide in vitro and how organic matter concentration affects in vitro sensitivity will improve fungicide selection for management of TARR. }, number={2}, journal={PLANT HEALTH PROGRESS}, author={Stephens, Cameron M. and Gannon, Travis W. and Thiessen, Lindsey D. and Cubeta, Marc A. and Kerns, James P.}, year={2023}, month={Jul}, pages={162–170} }
 @article{stephens_gannon_cubeta_sit_kerns_2022, title={Characterization and Aggressiveness of Take-All Root Rot Pathogens Isolated from Symptomatic Bermudagrass Putting Greens}, volume={112}, ISSN={["1943-7684"]}, DOI={10.1094/PHYTO-05-21-0215-R}, abstractNote={ Take-all root rot is a disease of ultradwarf bermudagrass putting greens caused by Gaeumannomyces graminis (Gg), Gaeumannomyces sp. (Gx), Gaeumannomyces graminicola (Ggram), Candidacolonium cynodontis (Cc), and Magnaporthiopsis cynodontis (Mc). Many etiological and epidemiological components of this disease remain unknown. Improving pathogen identification and our understanding of the aggressiveness of these pathogens along with growth at different temperatures will advance our knowledge of disease development to optimize management strategies. Take-all root rot pathogens were isolated from symptomatic bermudagrass root and stolon pieces from 16 different golf courses. Isolates of Gg, Gx, Ggram, Cc, and Mc were used to inoculate ‘Champion’ bermudagrass in an in planta aggressiveness assay. Each pathogen was also evaluated at 10, 15, 20, 25, 30, and 35°C to determine growth temperature optima. Infected plant tissue was used to develop a real-time PCR high-resolution melt assay for pathogen detection. This assay was able to differentiate each pathogen directly from infected plant tissue using a single primer pair. In general, Ggram, Gg, and Gx were the most aggressive while Cc and Mc exhibited moderate aggressiveness. Pathogens were more aggressive when incubated at 30°C compared with 20°C. While they grew optimally between 24.4 and 27.8°C, pathogens exhibited limited growth at 35°C and no growth at 10°C. These data provide important information on this disease and its causal agents that may improve take-all root rot management. }, number={4}, journal={PHYTOPATHOLOGY}, author={Stephens, Cameron M. and Gannon, Travis W. and Cubeta, Marc A. and Sit, Tim L. and Kerns, James P.}, year={2022}, month={Apr}, pages={811–819} }
 @article{rioux_stephens_koch_kabbage_kerns_2021, title={Identification of a tractable model system and oxalic acid-dependent symptom development of the dollar spot pathogen Clarireedia jacksonii}, volume={70}, ISSN={["1365-3059"]}, DOI={10.1111/ppa.13319}, abstractNote={Abstract}, number={3}, journal={PLANT PATHOLOGY}, author={Rioux, Renee A. and Stephens, Cameron M. and Koch, Paul L. and Kabbage, Mehdi and Kerns, James P.}, year={2021}, month={Apr}, pages={722–734} }
 @article{stephens_kerns_ahmed_gannon_2021, title={Influence of post-application irrigation and mowing timing on fungicide fate on a United States Golf Association golf course putting green}, volume={6}, ISSN={["1537-2537"]}, DOI={10.1002/jeq2.20249}, abstractNote={Abstract}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Stephens, Cameron M. and Kerns, James P. and Ahmed, Khalied A. and Gannon, Travis W.}, year={2021}, month={Jun} }
 @article{townsend_rioux_kabbage_stephens_kerns_koch_2020, title={Oxalic Acid Production inClarireedia jacksoniiIs Dictated by pH, Host Tissue, and Xylan}, volume={11}, ISSN={["1664-302X"]}, DOI={10.3389/fmicb.2020.01732}, abstractNote={Dollar spot is caused by the fungus Clarireedia jacksonii and is the most common disease of golf course turfgrass in temperate climates. Oxalic acid (OA) is an important pathogenicity factor in other fungal plant pathogens, such as the dicot pathogen Sclerotinia sclerotiorum, but its role in C. jacksonii pathogenicity on monocot hosts remains unclear. Herein, we assess fungal growth, OA concentration, and pH change in potato dextrose broth (PDB) following incubation of C. jacksonii. In addition, OA production by C. jacksonii and S. sclerotiorum was compared in PDB amended with creeping bentgrass or common plant cell wall components (cellulose, lignin, pectin, or xylan). Our results show that OA production is highly dependent on the environmental pH, with twice as much OA produced at pH 7 than pH 4 and a corresponding decrease in PDB pH from 7 to 5 following 96 h of C. jacksonii incubation. In contrast, no OA was produced or changes in pH observed when C. jacksonii was incubated in PDB at a pH of 4. Interestingly, C. jacksonii increased OA production in response to PDB amended with creeping bentgrass tissue and the cell wall component xylan, a major component of grass cell walls. S. sclerotiorum produced large amounts of OA relative to C. jacksonii regardless of treatment, and no treatment increased OA production by this fungus, though pectin suppressed S. sclerotiorum’s OA production. These results suggest that OA production by C. jacksonii is reliant on host specific components within the infection court, as well as the ambient pH of the foliar environment during its pathogenic development.}, journal={FRONTIERS IN MICROBIOLOGY}, author={Townsend, Ronald V and Rioux, Renee A. and Kabbage, Mehdi and Stephens, Cameron and Kerns, James P. and Koch, Paul}, year={2020}, month={Aug} }