The nights are cool and the dew heavy, creating the perfect environment for this fungus.
We've all seen this happen in summer. Your phlox, roses, bee balm, squash, and pumpkins are growing well, producing flowers and fruit.
Then, almost overnight, the leaves start turning white and eventually yellow and die. Not only is this ugly to look at in the flower garden, it curtails production in the veggie garden as well.
Powdery mildew is a ubiquitous fungal disease. With temperatures between 60 and 80 degrees and high humidity, powdery mildew spores start to take hold.
This year’s hot weather delayed the onset, but usually by August the nights are cool and the dew heavy, creating the perfect environment for this fungus.
There’s little you can do to stop powdery mildew from being around besides removing diseased leaves, fruits, and flowers.
If it starts on your squash, pumpkins, and melons late in the season, don’t worry. The plants are winding down anyway and it shouldn’t hurt production.
But on phlox, roses, bee balm and other flowers it can shorten their flowering period and just plain look ugly.
So, here’s what to do. First, grow disease-resistant varieties such as ‘Europeana’ rose, ‘David’ and ‘Orange Perfection’ phlox and ‘Marshall’s Delight’ bee balm.
Keep the plants well weeded and not crowded so the leaves dry quickly. Spray baking soda at a rate of one tablespoon per gallon of water on leaves as a preventive measure.
It’s thought baking soda changes the pH on the leaf making it less inviting for disease spores. Or use the organic spray Bacillus subtilis aka Serenade to control the disease at the onset. Bacillus subtilis is a bacteria that fights the fungal growth.
Next week on the Connecticut Garden Journal, I'll be talking about saving seeds. Until then, I'll be seeing you in the garden.
