Late Blight of Potato
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Late blight (Phytophthora infestans) symptoms may be observed on leaves, stems, and tubers. On leaves, individual lesions begin as water-soaked areas, which can enlarge quickly and result in extensive blighting (sudden death) of leaves. Under cool, humid conditions, sporulation (whitish-gray downy growth) can be observed on the undersides of affected leaves. Severely infected tubers are invaded by secondary organisms, resulting in a soft rot. This disease is relatively rare in Kentucky, and most likely to occur during periods of cool, wet weather (often in autumn).
Late blight on leaf.
(Photo: Howard F. Schwartz, Colorado State University, Bugwood.org)
Late blight on stem.
(Photo: Howard F. Schwartz, Colorado State University, Bugwood.org)
Late blight on tuber.
(Photo: R.W. Samson, Purdue University, Bugwood.org)
Management:
- Plant pathogen-free seed pieces
- Provide adequate plant spacing
- Maintain proper fertility
- Apply protectant fungicides
- Promptly destroy crop residues after harvest
- Avoid movement of infested soil to clean fields
