more than half of my plants (total about 100, from a wide variety of plant families, all on a large balcony) are affected
stems, roots, flowers and fruit show weak growth but no direct sign of the disease
what could be causing this?
how do i treat it?
will affected leaves spread the disease when composted?
It looks like white powdery mildew. Usually caused by improperly watering the plants. Water the plants at the base instead of the entire plant and try not to get water on the leaves. Remove badly affected leaves and put them in garbage (not in compost where it might spread). Try mixing up a solution using one tablespoon of baking soda to one liter of water and spray the affected parts of the plants. Give the plants lots of light as UV will help kill off the mildew. Use well drained pots and don't over water your plants unless they like wet feet.