I am gardening for the first time and, up until today, my tomato plants have been doing great, over 7 ft tall and getting flowers like crazy.
I walked on the porch this afternoon and their leaves are covered with white powdery mildew looking stuff. I made a few calls and was told to try spraying them with water and light dish soap. You are supposed to leave the dish soap mixture on for 20 minutes, then rinse off, as the soap can kill the plant, if you leave it on. I have tried this, but just this afternoon.