Black Dot

Pathogen: Colletotrichum coccodes

Symptoms

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Foliage - Brown spots on leaflets, petioles and stems. Yellowing, wilting and early death. Small black sclerotia develop at the base of the stem, on the stolons and roots.
Tubers - Grayish-brown lesions with sclerotia. Symptoms on the tubers resemble those of silver scurf.
In the field - The wilting and early death are similar to those that occur with Verticillium wilt.

Damage

When infestation is severe, plants collapse and there can be a severe decrease in yield. Tuber quality is also damaged by the development of silvery blemishes and black dots (sclerotia). Latently infected seed tubers can transmit the disease.

Conditions for Development

The fungus can survive for long periods in the form of sclerotia on and within the tubers, and also in vegetative remains. Other solani spps can serve as hosts for the disease. Colletotrichum is considered a weak pathogen that attacks plants under stress conditions, often accompanied by one or more other pathogens. The disease is more severe in light sandy soils, with minimal nitrogen, poor drainage, and high temperatures. When infested tubers are planted in fumigated soil, there can be more severe expression of disease.

Control

Varieties: There can be differences in susceptibility.
Pesticides: Seed treatments and soil treatments.
Management: Use of disease-free planting tubers, crop rotation, appropriate irrigation and fertilization.

Aerial Stem Rot
Black Dot, Colletotrichum coccodes
Blackleg and Tuber Soft Rot
Black Scurf, Rhizoctonia Canker
Common Scab, Streptomyces scabies
Early Blight, Alternaria solani
Deep Pitted Scab, Streptomyces spp
Leak, Pythium ultimum
PLRV, Potato Leafroll Virus
Powdery Scab, Spongospora subterranea
PVX, Potato Virus X
PVY, Potato Virus Y
Verticillium Wilt, Verticillium dahliae