Pacific Pests, Pathogens and Weeds - Online edition

Pacific Pests, Pathogens, Weeds & Pesticides

Yam leaf spot (312)

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  • 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.
Common Name

Yam leaf spot

Scientific Name

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.

AUTHORS Grahame Jackson & Eric McKenzie 
Information (and Photos 1-3) used in this fact sheet is taken from McKenzie E (2013) Guignardia dioscoreae: PaDIL - (

Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.

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