Potato Black dot

Caused by the fungal pathogen: Colletotrichum coccodes

Black dot may cause up to 30% reduction in yield due to early dying .

Optimal temperatures for black dot development range between 20-30C

The disease is characterized by the formation of black sclerotia on the roots, the stems and the tubers of potatoes as the plants mature and die.

On tubers sclerotia may be formed in small patches causing brown – gray blemishes resembling those of Silver scurf.

Stressed plants may demonstrate early dying and higher disease severity than non-stressed plants.

C. coccodes host plants: nightshade, velvetleaf, yellow mustard, spring canola, soybean, alfalfa, oat

C. coccodes non-host plants: barley, corn, rye, wheat – preferred for crop rotations

Russet Burbank potatoes showing early-dying symptoms due to black dot	Acervuli (sub-epidermal fruiting body) with setae ("thorn" like structures)
C. coccodes sclerotia on stolon end of tuber	Blemishes on tuber