Look closely at the image below:
See the gray fuzz on those tomato leaves? I think that's powdery mildew. This is what it looks like when it's further along:
Yellow, withered leaves, curling up on the tomato plant. I attended a workshop at BNAN City Natives this morning and learned that the powdery mildew is unusual for most home gardeners in the Northeast right now, because it has been so hot. But because I have been growing these tomatoes in self-watering containers, they always have access to water. And so does the fungus that causes mildew. It doesn't help that my backyard is shady, getting maximum 5-6 hours of sunlight.
I started by plucking the affected leaves, but this wasn't effective.
The mildew started to spread from its original hosts to its neighbors, so I decided to harvest the green tomatoes and pull the two plants most heavily affected.
Erica, garden educator at BNAN, recommended that I spray the less affected plants with a copper sulfate spray, available at hardware and gardening stores. She said to look for a spray certified by OMRI (Organic Materials Review Institute).
Prevention for mildew would be better drainage - next year, I will introduce more sand into the soil mix, and maybe drill a couple of extra drainage holes.
What diseases have you had in your garden and how do you deal with them?