Time to act:
Jan, Feb, Jun, Jul, Aug, Sep, Oct, Nov, Dec
Caused by the same fungus responsible for tomato blight, potato blight causes the leaves to develop dark patches, starting at the edges. In humid conditions a white fungus appears around the marks. The infection then travels down the plant to the tubers, which turn a reddish-brown and, if a secondary infection strikes, the crop turns slimy and rots.
Here are organic and chemical ways of dealing with the problem.
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