Circular brown spots with light-brown/grey centers, surrounded by a wide dark brown ring and and yellow halos, around 15 mm wide appear on leaves. The spots mostly occur between the veins and also on the margins. Sometimes spots grow into large blotches, and a leaf bligh occurs. This usually happens in cooler, wet areas above 600 m altitude. Infections on the berries are generally smaller, around 5 mm wide, but sometimes they cover the whole berry. Generally, they are more irregular in shape than on the leaves, and mainly on the side exposed to the sun. In severe cases, premature leaf fall and stem dieback can occur.
The spots are caused by the fungus Mycosphaerella coffeicola. It favors periods of high humidity, high rainfall, warm temperatures and drought stress, especially after the flowering stage. The pathogen survives in leaf debris. The spores are spread by wind and rain splash, and through human movement through fields, particularly when plants are wet and need water to germinate. Young and unshaded trees are most vulnerable.
As of today, no biological control solution seems to be available against this disease. Please contact us if you know of any.
Always consider an integrated approach with preventive measures together with biological treatments if available. If it is required, use products such as coppers or triazoles. Apply sprays of copper for three months beginning at flowering. Note, copper fungicides may kill beneficial insects.