Initial symptoms show small, elongated, oval-shaped spots that are dark green to reddish-brown with yellow halos. Older symptoms are characterised by large and elongated lesions with irregular outlines and red-brown margins. The spots may join together to form larger patches, which can result in chlorosis and necrosis.
The damage is caused by the fungus Epicoccum sorghinum, and is spread by the wind- or rain-borne spores of the fungus. The fungus requires warm, humid conditions to multiply. It generally affects the oldest leaves, hence it is considered as a minor disease with little economic importance.
Use Calcium Silicate Slag as a soil amendment to reduce ring spot severity.
Always consider an integrated approach with preventive measures together with biological treatments, if available. As of today, no chemical control methods have been developed against these fungi.