Biology, Epidemiology, and Management of Spring Dead Spot of Bermudagrass

Spring dead spot (Ophiosphaerella spp.) (SDS) of bermudagrass (Cynodon dactylon (L.) Pers. x transvaalensis Burtt Davy) is one of the most challenging diseases in the United States transition zone. Six projects were conducted from 2019 to 2022 to better understand the environmental, edaphic, and spatial distribution of SDS epidemics and to examine management strategies for SDS with chemical and cultural practices. A survey of 51 locations provided support of the geographic distribution of Ophiosphaerella species across the Mid-Atlantic United States. Ophiosphaerella herpotricha and O. korrae were isolated from the Mid-Atlantic region, yet O. narmari was not. Cultivars in which parent material originated from the midwestern United States had predominantly O. herpotricha and cultivars in which the parent material originated from the southeastern United States had predominantly O. korrae. In vitro and in situ fungicide efficacy screenings were conducted for O. herpotricha and O. korrae. Additionally, field studies were conducted to optimize fungicide applications and bermudagrass recovery from SDS. Results highlighted that, generally, O. korrae was less sensitive to fungicides than O. herpotricha; the fungicides isofetamid, mefentrifluconazole, penthiopyrad, and pydiflumetofen were generally the most efficacious against SDS; the different fungicide application methods deployed produced mixed results in their effect on fungicide efficacy against SDS with increased efficacy of tebuconazole against SDS with soil surfactant applications and post-application irrigation in certain scenarios; the optimal timing for fungicide applications for SDS was from 13-18°C with tebuconazole and 13-21°C with isofetamid; and nitrogen applications without cultivation practices in the late spring/early summer optimized bermudagrass recovery from SDS. Lastly, a geospatial survey study was conducted to determine the environmental and edaphic factors that influence SDS epidemics. Results were variable with numerous environmental and edaphic factors influencing SDS depending on the year and location; however, soil pH, soil potassium content, and thatch depth were among the most consistent and influential factors on SDS epidemics. Ultimately, these data improve our recommended strategies for successful SDS management.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Plant Pathology, Physiology and Weed Science

Department dc:contributor.department

Plant Pathology, Physiology and Weed Science

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2022

Author dc:creator

• Hutchens, Wendell Joseph

Chair dc:contributor.committeechair

• McCall, David S.

Committee members dc:contributor.committeemember

• Nita, Mizuho
• Goatley, J. Michael Jr.
• Kerns, James Patrick

• turfgrass
• plant disease
• pathology
• Ophiosphaerella herpotricha
• Ophiosphaerella korrae

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:34206

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/109643