How can I effectively prevent and treat fungus on tomato plants?

To prevent and treat fungus on tomato plants, you can:

1. Plant tomatoes in well-drained soil and provide good air circulation.
2. Water the plants at the base to avoid wetting the leaves.
3. Apply fungicides as a preventive measure or at the first signs of fungus.
4. Remove and destroy any infected plant parts to prevent the spread of the fungus.