Sorry for late reply…..life gets in the way sometimes.
I’ve planted both, disease free (supposed) and left overs. No difference, both have black spots. But….on one occasion my potatoes flooded for a couple days! I didn’t like it and this spring plan to create more drainage on the downhill end.
Thank you for the tip!
Causes of Black Spots
Physiological Disorders: High moisture content at harvest can lead to internal black spots, often referred to as “black heart.” This occurs when potatoes are exposed to low oxygen levels, causing internal browning.
Bruising: Excess moisture can make potatoes more susceptible to bruising during handling. Bruised areas can develop black spots as the cells are damaged, leading to discoloration.
Fungal Infections: High moisture levels can promote fungal diseases, such as black scurf, caused by the fungus Rhizoctonia solani. This can lead to black lesions on the skin of the potato.
Black scurf, caused by the fungus Rhizoctonia solani, appears as small, irregular black lesions on the skin of potatoes. While these lesions are unsightly, they do not affect the potato’s internal quality and can be removed by peeling.
To treat black scurf caused by Rhizoctonia solani, use certified seed tubers free from sclerotia, apply fungicides to seed pieces, and practice crop rotation to reduce soilborne inoculum. Additionally, ensure proper planting depth and avoid overwatering to promote healthy plant growth.
Fungicide soil application effi ciency for the control of black scurf (Rhizoctonia solani) on three potato cultivars
By Journal of Applied Horticulture
or
Excellent article from Cornell University