The spores are spread rapidly in warm, wet conditions, especially when the temperature is above 10°C and humidity is above 75% for several straight days. Often, the spores may fall to the ground, during rain, entering the soil, or may travel miles in the wind.* Early signs include black spots on leaf tips and white mold under the leaves in humid conditions. Infected tubers develop gray or reddish-brown patches and quickly decay into foul-smelling mush. FTP, what is this 
The spores are spread rapidly in warm, wet conditions, especially when the temperature is above 10°C and humidity is above 75% for several straight days. Often, the spores may fall to the ground, during rain, entering the soil, or may travel miles in the wind.* Early signs include black spots on leaf tips and white mold under the leaves in humid conditions. Infected tubers develop gray or reddish-brown patches and quickly decay into foul-smelling mush. FTP, what is this disease, caused by an oomycete, largely responsible for the 1847 Irish potato famine?
The spores are spread rapidly in warm, wet conditions, especially when the temperature is above 10°C and humidity is above 75% for several straight days.
Potato Blight or Phytophthora infestans