Biology
The spores of this oomycete over-winter on infected tubers, particularly those that are left in the ground after the previous year's harvest; in cull piles, soil or infected volunteer plants and are spread rapidly in warm and wet conditions. This can have devastating effects by destroying entire crops.
Spores develop on the leaves, spreading through the crop when temperatures are above 10 °C (50 °F) and humidity is over 75%-80% for 2 days or more. Rain can wash spores into the soil where they infect young tubers. Spores can also travel long distances on the wind.
The early stages of blight are easily missed, and not all plants are affected at once. Symptoms include the appearance of dark blotches on leaf tips and plant stems. White mould will appear under the leaves in humid conditions and the whole plant may quickly collapse. Infected tubers develop grey or dark patches that are reddish brown beneath the skin, and quickly decay to a foul-smelling mush caused by the infestation of secondary soft bacterial rots. Seemingly healthy tubers may rot later when in store.
Read more about this topic: Phytophthora Infestans
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