Tomatoes are one of the easiest garden plants to grow, and don't require a lot of special knowledge or care. On the other hand, they are susceptible to a large number of diseases and problems. While not all of these diseases can be treated, most tomato plants can be protected by treating them before any problems start. Most of the treatments will also result in larger crops and healthier plants.
Water regularly and properly. Regular waterings, and not allowing the soil to dry completely between waterings will help prevent growth cracks, blossom end rot and septoria leaf spot. Water whenever the soil is only slightly damp when you push a finger into it. Avoid overhead watering, such as sprinklers, which can damage leaves and promote disease by splashing soil on to the leaves. Regular watering also prevents the tomato plant from becoming stressed, which could leave it more susceptible to other diseases.
Add a layer of mulch. A thick layer of mulch around the base of a tomato plant keeps in valuable moisture, prevents weeds that can transmit diseases and keep leaves from coming in contact with soil, which can also transmit diseases.
Pinch off low-hanging leaves. Keeping leaves away from direct contact with the ground can stop the spread of some tomato diseases.
Mix 1/2 teaspoon of anti-transpirant, such as Wilt-Pruf, VaporGard, or any other brand, with one cup of skim milk and one gallon of water.
Spray the anti-transpirant mixture on the tomato plant, making sure to also spray the underside of leaves. The spray treatment will help protect the plant against a number of common tomato diseases, such as spotted wilt virus and tomato mosaic virus.