Epsom salts worked for me. Dissolve 1 tablespoon of epsom salts in one gallon of water and add this solution to the spray bottle. After the plants begin flowering, generously spray them with the solution. Or take a look at this info.
Read more: How to Use Epsom Salts for Tomato Black Rot | eHow.com
How to Use Epsom Salts for Tomato Black Rot | eHow.com