A problem on a wide variety of plants. Yellow, discoloured areas develop on upper leaf surfaces with greyish -white fungal growth beneath. The affected leaves turn a dull grey-brown colour and become very thin on the affected areas. Eventually spreads over the entire leaf or plant. Downy mildew is common on young plants and those growing in moist environments.
Cultural measures: Remove infected leaves immediately and improve air circulation around plants and in greenhouse.
Remove all debris around plants. Avoid overhead watering.
There is currently no chemical control available for downy mildew.