Tomato fungal diseases cause spots on leaves and fruit, limiting the tomato plant's ability to produce food through photosynthesis. This reduction in energy yields smaller, weaker plants and less fruit. Tomato blights can be difficult to control, but you can use some cultural methods to reduce the chance of infection in your garden.
Plant a healthy, disease-resistant variety of tomato plant. Vigorous, healthy seedlings are better able to resist fungus and disease.
Rotate your tomato planting area each year.
Remove and destroy your tomato plants and all plant residue after your final harvest. Fungal spores overwinter in plant residue and can infect new plants the following season.
Water your tomato plants from the bottom with drip lines or a hose, and avoid getting water on the foliage.
Work with your tomato plants only when they are dry. Moisture on the leaves, from rain or sprinklers, can facilitate the spread of fungal spores.
Keep the area in and around your garden clear of weeds, which can host diseases. Mulching your tomato plants helps control weeds and retain moisture.
Control insect pests with chemical insecticides or beneficial insects such as ladybugs. Insect pests can spread diseases from plant to plant.
Monitor your plants daily and apply a fungicide according to label directions as soon as you find leaf spots or other signs of tomato fungal infection.