Early blight disease skin#
Presence of these sclerotia may be minimized by harvesting tubers soon after vine-kill and skin set. Irregular, black hard masses on the tuber surface are overwintering structures (sclerotia) of the fungus. Black Scurf and Rhizoctonia Canker ( Rhizoctonia solani)īlack scurf is purely cosmetic and does not reduce yield, even in storage. Tubers may also become dried out and wrinkled due to excessive moisture loss in storage. In storage, lesions may darken and the skin may slough off and many small circular lesions may coalesce to form large affected areas. Lesions are initiated at the stolon end as small pale brown spots which may be difficult to detect at harvest but will continue to develop in storage. Silver scurf affects only tuber periderm (skin). Symptoms on tubers can be easily mistaken for silver scurf. Under a 10X lens, tiny black sclerotia are visible on the surface of the affected tissue. On potato foliage, symptoms of black dot are nearly indistinguishable from those of early blight. On tubers, it produces tiny black sclerotia (fungal resting structures). Averre Black Dot ( Colletotrichum coccodes) Extensive rotting causes the tissue to shrink and collapse, usually leaving a dark sunken area on the outside of the tuber and internal cavities. The pathogen penetrates the tuber, often rotting out the center. The rot may develop at an injury site such as a bruise or cut. Jenson Fusarium Dry Rot ( Fusarium spp.)įusarium dry rot causes internal light to dark brown or black dry rot of the potato tuber. Lesions can increase in size during storage and tubers become shriveled. The underlying flesh is dry, leathery, and brown. Tuber lesions are dark, sunken, and circular often bordered by purple to gray raised tissue.
Early blight disease full#
Samson Early blight ( Alternaria solani)įor more detailed information on this disease, please see our full Solanaceous, Early Blight article.Įarly blight usually affects potato foliage but tuber infections can also occur. Common scab is controlled or greatly suppressed at soil pH levels of 5.2 or lower, though a closely related but less common species of Streptomyces known as acid scab can survive down to 4.0. The type of lesion is dependent on potato cultivar, tuber maturity at infection, organic matter content of soil, strain of the pathogen, and the environment. Scab may be superficial (russet scab), slightly raised (erumpent scab), or sunken (pitted scab). Common Scab ( Streptomyces spp.)įor more detailed information on this disease, please see our full Potato, Scab article.Ĭommon scab produces tan to dark brown, circular or irregular lesions which are rough in texture. Proper identification will help you decide which tubers will store well and which should be sold as tablestock, and will give you a better idea of which soil-borne diseases are present in your fields, improving your future crop rotations. There are many diseases that affect potato tubers, so as you sort through your potato harvest each year, take a moment to check for disease symptoms.
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