It is the season for Cercospora leafspot, the most damaging foliar disease of sugarbeet resulting in lower tonnage and reduced sucrose content. The fungus Cercospora beticola causes Cercospora leafspot . The most common source of the Cercospora fungus is infected sugarbeet debris in the field. The fungus is spread mainly by wind and water. Cercospora leafspot develops rapidly in humid, warm and rainy weather.
Spore release is effected by rain and dew.
Day temperature of 80-90 F and night temperatures above 60 F favor disease development. Leafspot symptoms may occur about 5-7 days after infection. Individual spots may coalesce and kill entire leaves, particularly on susceptible varieties. In humid conditions, the spots may become gray and velvety with the production of spores. These spores can further spread the disease, especially within fields, resulting in many infection cycles during the growing season.