Answer: The fungus that caused the potato famine is Phytophthora, also called Late Blight, and it is active in many gardens across the U.S. Any part of the plant can be infected by this fungus. When the roots of stems are infected, wilting of the plant will be evident. This disease is most likely to occur during or after periods of excessive rains where water stands for a period of time in the garden.
A protective application of chlorothalonil containing fungicide should help save your plants. (Ortho Multi Purpose Fungicide, Dragon Daconil 2787, Ferti-lome Liquid Fungicide). You should continue repeat applications of the fungicide at seven day intervals. After your plants have died off, you will need to remove all debris from your garden, including the roots. Be sure you are diligent in cleaning up and destroying and plant debris post-harvest so there is nothing for phytophthora infestans to over winter on.
Hope this information is helpful.
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