Fluctuations in Number of Cercospora beticola Conidia in Relationship to Environment and Disease Severity in Sugar Beet

• Published in: Phytopathology Vol. 99; no. 7; pp. 796 - 801
• Main Authors: Khan, J, Qi, A, Khan, M.F.R
• Format: Journal Article
• Language: English
• Published: St. Paul, MN American Phytopathological Society 01.07.2009
• Subjects: Air Microbiology; air temperature; airborne microorganisms; Ascomycota - cytology; Beta vulgaris - microbiology; Beta vulgaris subsp. vulgaris; Biological and medical sciences; Cercospora beticola; conidia; conidia dispersion; correlation; disease severity; Environment; environmental factors; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; Fungal plant pathogens; inoculum density; Minnesota; North Dakota; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - microbiology; relative humidity; seasonal variation; Spores, Fungal - cytology; sporulation; sugar beet; Time Factors; North Dakota; Minnesota; Fungi; Plant pathology; Plant; Microbiology; Plant pathogen; Cercospora beticola; Environment; Fungi Imperfecti
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO-99-7-0796

Cercospora leaf spot, caused by Cercospora beticola, is the most damaging foliar disease of sugar beet in Minnesota (MN) and North Dakota (ND). Research was conducted to characterize the temporal progression of aerial concentration of C. beticola conidia in association with the environment and disease severity in sugar beet. In 2003 and 2004, volumetric spore traps were placed within inoculated sugar beet plots to determine daily dispersal of conidia at Breckenridge, MN, and St. Thomas, ND. Plots were rated weekly for disease severity. At both locations, conidia were first collected in early July 2003 and late June in 2004. Peaks of conidia per cubic meter of air were observed with maxima in late August 2003 and in early September 2004 at both locations. Peaks of airborne conidium concentration were significantly correlated with the average temperature of daily hours when relative humidity was greater than 87%. Weekly mean hourly conidia per cubic meter of air was significantly (P < 0.01) associated with disease severity during both years and across locations. This study showed that C. beticola conidial numbers may be used to estimate potential disease severity that, with further research, could be incorporated in a disease forecasting model to rationalize Cercospora leaf spot management.