Downy mildew of Cucurbits
They cause lesions on the upper leaf surface, bordered by the veins, which are first yellow and then turn brown. On the underside of the leave fluffy growth [...] For most downy mildews, the optimum temperature is around 15 o C and the closer the temperature is to this, the shorter the leaf wetness period that is [...] Inside the plant, the pathogens produce haustoria, small organs with which the pathogen can take up nutrients from the living plant cells. The pathogens