Growing tomatoes provides a bounty of fruits for salads, sauces and many dishes. Insect and diseases attack tomatoes. These problems require insecticides and fungicides. Many natural fungicides are alternatives to synthetic solutions.
Leaf spot cause circular spots with dark margins and spots in the center of lower leaves. Early blight cause large, circular brown spots with concentric rings. Late blight cause dark areas that creep in from leaf edges. Soil rot can cause brown, rotted areas on the sides of fruit. Powdery mildew causes a powdery residue on leaves. Fusarium wilt demonstrates as yellow, wilted leaves. Verticillium wilt shows as yellowing of leaves and browning of the veins. Many of these fungi live for years in the soil causing problems year after year, according to North Dakota State University plant specialists H. Arthur Lamey and Martin A. Draper. Regular application of natural antifungal compounds minimizes the damage from these diseases.
Sulfur is one of the oldest fungicides used for more than 2000 years, according to Purdue University botanist, Janna Beckerman. Dust the sulfur compound on all parts of the plant and undersides of leaves. Do not use sulfur if you have applied an oil spray on the plant within the past month. This combination of compounds can cause phytotoxicity, which kills the plants.
Herbal oils from garlic, fenugreek, cumin, mint and clove help inhibit fungal growth on plants. Basil oil also limits soil pathogens. These herbal compounds provide protection against fungus problems without the use of toxic chemicals.
Neem oil is extracted from the neem tree from India and Southeast Asia. It is a compound with natural insecticidal and antifungal properties now being widely used as a natural fungicide spray for many types of plants, including food crops such as tomatoes.
Common baking soda is a natural fungicide. Mix 1 tbsp. of baking soda with 1 gallon of water. Add ¼ to ½ tsp. of liquid soap and thoroughly blend the mix. Apply it weekly to all parts of the plant to control powdery mildew and black spot, according to the Brooklyn Botanical Garden site. Monitor plants for any cellular damage from the detergent.