Black Dot

 

Black Dot is a common potato disease, normally noticeable on tubers but affects the entire plant.

Black dot can normally be identified by a dark brown to grey blemish on the potato’s surface. The visible black dots (black microsclerotia) often give the potatoes a ‘sooty’ looking appearance, which can develop into a silvery looking sheen during storage.

Black dot can affect all parts of the plant not just the tubers – stems, roots and stolons can also be infected  Black dot causes wilt symptoms above ground and severe rotting of roots, shoots and stolons below ground, leading to discoloured tubers, plant decline and a reduction in yield.

 

Common Causes and Conditions of Black Dot

Black Dot infection is caused by the fungus ‘Colletotrichum coccodes’, and comes from both infected tubers and soil, where the fungus survives on plant debris between host crops.

Development of Black Dot on the tubers is normally encouraged by wet growing conditions and may be further encouraged by irrigation.  Symptoms on tubers may develop during storage and favour warm, moist conditions.

 

Affected / Vulnerable Varieties

Potato Varieties which tend to be more susceptible to Black Dot include Desiree, Estima and Maris Piper.

 

Control of Black Dot

Cultural and Methods:
Avoid severely affected seed potatoes, harvest early and maintain dry, cool storage conditions.

Chemicals and Pesticides:
Currently there are no chemicals approved in the UK that give adequate control and protection against Black Dot.

 

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