Be sure the variety you select has resistance to Verticillium wilt, Fusarium wilt, and nematodes. It will also help cut down on fruit lost to blossom-end rot and cracking and can reduce early blight. Tomato plants should be pruned and supported. Prune by breaking off the suckers that develop just above where the leaves are attached to the main stem. Pruning controls the growth so the main stem can be supported more easily.
Foliar diseases are also much easier to control where suckers are pruned.
Pruning off suckers may slightly reduce yield per plant, but well- pruned plants can be planted as close as 12 inches apart. The yields of closely spaced, pruned plants more than compensate for the yield reduction from pruning. It is important to support tomato plants to keep them from toppling over and letting the fruit rest on the ground. When tomato plants fall over, they spread out, exposing the fruit to the sun. This results in a large portion of fruit being lost to sunscald or soil rot.