How to Cure Tomato Blight

Clip off infected parts of the tomato plant to control spread. Using sharp, sterilized pruning scissors, cut brown, spotted or mushy foliage, stems and fruit. Collect the clippings in a garbage bag to keep the fungal spores from spreading. Rub the blades with cotton dipped in rubbing alcohol between cuttings to prevent spread.

Spray tomatoes with organic sulfur spray as soon as you notice brown or yellow spots forming on older foliage.

Apply a copper-based fungicide if symptoms of the blight persist despite control strategies. Follow label directions for application rates when spraying the fungicide over tomato plants. In general, apply the selected formulation as soon as symptoms of disease are observed and repeat application every week to 10 days during warm, wet weather. Cover both the upper and lower surfaces of leaves thoroughly, to the point of runoff, to ensure complete and adequate coverage.

Collect plant debris and crop residue at the end of the growing season and destroy to kill spores and keep them from overwintering. Alternatively, plow the residue into the soil to break up microorganisms and prevent the diseases from recurring on other plants.

Grow tomatoes on trellises or tomato cages as opposed to letting them sprawl on the ground. A tomato cage improves air circulation and dries the foliage soon after you irrigated the soil, reducing the chances of fungal diseases.

Spread 2 to 3 inches of organic mulch, including dried glass clippings, wood chips or straw, around each tomato plant to reduce chances of fungal spores spreading through splashing water. Mulching also retains soil moisture and keeps the plant's roots cool during the summer.