What kind of disease, how can I remedy that? Lower leaves develop brown edges, curl and wilt. Then the stem wilts, and I can easily get it off the plant.
This looks more like a moisture issue instead of a disease or pest.
You will need to water throughly daily and even twice a day when temperatures are above 80 degrees.
Your tomato plant also needs a support. You can purchase tomato cages or use stakes to support your plant.
Here are some links that will help you.