Caused by parasitic organisms that are closely related to algae (not a true fungus). Most likely to appear during wet, cool weather. First symptoms could be mottling of spotting of the leaves (could be yellow, light green, brown or purple. You will also see a fuzzy, soft looking growth that can be white, grey, brown or purple. This will mostly appear on the underside of bottom leaves , but can take over the entire plant.
- Affects
- Level of Concern
- Gardeners take note
- What months
- Jun–Sep
- Treatment / Useful Links
To prevent downy mildew from effecting plants, water from below (use drip irrigation instead of spray) and avoid getting foliage wet. Also, clean up dead plant material in the fall, as the disease can overwinter there. Once plants have downy mildew, your best bet is to selectively prune to improve air circulation. Try to eliminate moisture on leaves if possible (water from below). If mildew takes over too much of the plant, the entire plant should be removed from the garden so disease doesn’t spread to other plants.