• Widespread distribution. On all yam species, but most common on Asiatic yam (or lesser yam), Dioscorea esculenta. A minor disease, unlikely to affect yield.
• Leaf spots, circular or irregular, up to 10 mm diameter, tan or grey, merging, with dark brown or black borders. Fruitbodies can be seen as black pin points in the spots.
• Spread occurs when spores ooze from fruitbodies during wet weather and splashed by rain or carried by wind.
• Cultural control: collect debris (vines and leaves) and destroy after harvest; 2-3 year crop rotations; test varieties for differences in tolerance.
• Chemical control: unlikely to be needed, but if required use chlorothalonil, copper, or mancozeb.

Yam leaf spot

Guignardia dioscoreae. Previously known as Guignardia dioscoreae-bulbiferae and Phyllostricta dioscoreae. Guignaria is the sexual state, and Phyllosticta dioscoreae is the asexual state, i.e., spores are produced without mating strains combining.