shule1

Prevention is sometimes the best policy. I understand maybe it can't be prevented very easily in extra humid gardens, though.

Here's what I like to do if I'm trying hard to avoid the plants getting diseased:

1. I start my plants outdoors in a small, unheated greenhouse. They had a lot more disease issues later in the season when I started them indoors. All that fresh air and natural sunlight must be good for them. If you do start indoors, I recommend air circulation, and never use outdoor soil indoors.
2. I avoid buying plants. I start from seed. Store-bought plants sometimes carry pests and/or diseases, although they can do just fine still. I'm not against buying plants (but if I'm trying hard to avoid diseases avoiding buying plants may reduce the risk).
3. I make sure the pre-transplant plants are strong and that they have plenty of the nutrients they need.
4. I zap seeds I plant in water with a Z4EX before drying or planting.
5. I don't worry about it too much. I think this helps a lot, honestly. Getting worked up over a diseased plant or a disease that might develop in future can sometimes cause more problems than it solves. I mean, sometimes it's not even a disease. I tossed my biggest Paul Robeson plant just because it had edema once (before I knew what edema was). It seemed to be contagious, and scary at the time, but it's pretty harmless. Don't get me wrong, diseases can wreak havoc sometimes, but don't let them control you if you can help it. You can live and learn from what happens. If you never just relax you may never learn the times when you can safely do so.
6. Don't plant tomatoes next to ground cherries. (Ground cherries can harbor spider mites, which may take an interest in nearby tomatoes. Spider mites can spread anthracnose, I believe.)

Anyway, yeah, this isn't meant to take away from what others have said. Most people here probably have more experience than me with dealing with tomato diseases.