white spots on tomato leaves and stem
I have some beefsteak tomato plants that're coming along nicely, and the plants are about 2-3 ft tall. There aren't any tomatoes yet. Recently, the leaves on some of the plants started developing some round powdery white spots. The spots sort of look like mold or powdered sugar. The spots are starting to spread and even appear on the stems. Does anyone have any idea what this is and what I should do about it? I've searched a lot of gardening web sites and can only find references to black, brown, or yellow spots.
A pic of the problem is below, and you can click on it to see 3 more pics.