Efficacy of demethylation inhibitors fungicide, biocontrol strategies, and cultural practices on managing Clarireedia spp., in turfgrass
Open Access
- Author:
- Shah, Kabita
- Graduate Program:
- Agricultural and Environmental Plant Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 28, 2023
- Committee Members:
- Erin Connolly, Program Head/Chair
John Edward Kaminski, III, Thesis Advisor/Co-Advisor
Peter Landschoot, Committee Member
Fereshteh Shahoveisi, Committee Member - Keywords:
- Dollar spot
Clarireedia jacksonii
Chemical control
Demethylation-inhibiting fungicides
Plant growth regulators (PGR)
invitrosensitivity assay
biological control
cultural control
management practices
turfgrass
Disease severity - Abstract:
- Dollar spot, caused by the pathogen Clarireedia jacksonii, is a common turfgrass disease that requires a comprehensive management approach for effective control. These include a combination of cultural and chemical options and biological strategies to minimize disease severity. Two studies were designed to evaluate the efficacy of commercially available demethylation-inhibiting fungicides in suppressing a moderately insensitive population of C. jacksonii and to determine the influence of dew removal, plant growth regulators (PGR), and nitrogen (N) on dollar spot severity. This research aims to understand how chemical fungicides suppress dollar spot, determine the in vitro growth suppression differences among C. jacksonii isolates and the different DMI fungicides, and understand the factorial relationship between daily dew removal, nitrogen, and PGR application on DS severity. One field study was conducted in 2021 and 2022 at Mountain View Country Club (MVCC), Boalsburg, PA. We posited that application of these DMI fungicides at 14-day (low concentration) and 21-day (high concentration) intervals on golf course fairways would provide variable disease suppression. Based on data analysis from 2021 and 2022, most of the DMI fungicides assessed could achieve excellent control of a moderately insensitive population of C. jacksonii. Results imply inherent differences in dollar spot suppression across DMI fungicides, providing insights for managing resistant dollar spot populations. The second field study was conducted at the Joseph Valentine Turfgrass Research Center (JVTRC) on a putting green and fairway. This 2-year study sought to determine the influence of cultural practices (i.e., dew removal, N, and PGR) on dollar spot severity. Contrary to previous findings, our research indicated that the PGR prohexadione-Ca might negatively influence dollar spot severity, while applying N and removing dew generally reduced disease severity. An interesting finding was that removing the dew negated the positive impact of applying N and the negative impact of PGR compared to the plots not having the dew removed. In conclusion, based on the findings of this experiment, it is recommended to incorporate a combination of cultural (N and dew removal) and chemical options (DMI fungicide) to manage dollar spot successfully. Further study and careful consideration of these findings will assist practitioners in optimizing their disease control strategies for turfgrass affected by dollar spot.