Phytophthora blight
stem. On potato tubers, blueish lesions appear, that can be seen through the skin. The Great Famine was a period of mass starvation caused by this disease [...] temperatures between 15 and 23 °C and higher water content than is optimal for crop growth. Phytophthora overwinters in roots, infected tubers and bulbs [...] either by germinating sporangia or by zoospores produced in the sporangia. For germination on above-ground plant parts, leaf wetness is required. Dispersal