1. Disinfect tools, tomato cages and stakes. 

2. Rotate the planting location every three to five years.

3. Do not plant in cold soils. This weakens plants making them more susceptible to diseases and may stunt them permanently. 

4. Do not crowd tomatoes. Good air circulation around plants is vital in keeping the foliage dry and preventing diseases. 

5. Remove the lower branches, leaving the stem bare up to the first set of the flowers and then mulch (straw is a good choice). Many fungal diseases are in the soil or in bits of plant material left over from previous year. When it rains, fungal spores splash up onto the lower leaves, infecting them. The next time it rains, the spores from the infected leaves splash up onto the next set of leaves. Unchecked, the infection will spread all the way to the top of the plant.

6. Water in the morning to give the foliage time to dry out before nightfall. 

7. Remove any diseased looking leaves as soon as possible. 

8. At the end of every growing season, remove as much of the plant as possible from the garden and do not compost.