Leaf spot detections in Michigan sugarbeet fields
Cercospora and Alternaria leaf spot have been detected in Tuscola County in 2019.
Cercospora and Alternaria leaf spot were detected in the Michigan sugarbeet production region. Lesions were found at the Saginaw Valley Research and Extension Center on June 17, 2019 and in a local commercial field on June 18, 2019. Severity was generally low in these fields, however, high pressure areas of early (April) planted fields may be at risk of increased infection.
Cercospora leaf spot is caused by Cercospora beticola, a fungus that is favored by warmer temperatures (75-95 degrees Fahrenheit) and high humidity. Alternaria leaf spot is caused by various Alternaria spp., which are fungi that are favored by relatively cool temperatures and high humidity. Despite cooler air temperatures in Michigan this season, high humidity conditions have been conducive for the development of both diseases, as confirmed by these first spot reports.
Detecting a Cercospora leaf spot lesion this time of the year is not unexpected, as the first lesion in the growing area last year was detected on June 15. However, you should begin actively scouting fields for the disease. Also, consider applying a protectant fungicide if you have an early planted field, if you have a susceptible variety or if your field is located adjacent to an inoculum source, such as a field that was planted to sugarbeets last year.
Monitor local risk levels, track recent detections and consult recent research findings to assist in management decisions. A summary of recent local research is provided in the 2018 Michigan Sugarbeet Research & Education Advisory Council (REACh) Research Results and current recommendations can be found in the 2019 Growers’ Guide for Producing Quality Sugarbeets.