Many different kinds of blight affect a variety of plants. Fire blight affects trees and shrubs, while alternaria leaf blight is commonly found on melons. One homemade solution is a simple baking soda mixture that is effective against several problems. In addition to fungal sprays for blight diseases, proper gardening practices minimize problems. Provide adequate sun and water, depending on the plant variety and don't crowd plants, which encourages disease.
A homemade concoction that includes baking soda treats some blight diseases, according to the University of Florida IFAS Extension. Mix 2 tbsp. each of baking soda, baby shampoo and vegetable oil with 1 gallon of water. Pour the mixture into a spray bottle, storing any remaining solution in a covered container. In addition to controlling early blight in tomatoes and alternaria leaf blight on cucurbits, this solution also controls aphids, leafhoppers and mites, as well as powdery mildew disease.
Water infected plants the day before applying treatments. Spray both the tops and bottoms of the leaves with the baking soda solution early in the day or in the evening. Spraying them with oil during the heat of the day may scorch the leaves. Reapply the solution every five to seven days or more frequently in hot, humid weather.
Before applying any remedy, positively identify the disease or pest. Applying the wrong treatment wastes time and money, and may aggravate the condition. Spray the solution on one small area of the plant and wait before treating the entire plant. Watch for signs of phytotoxicity, such as yellowing leaves or spots, which is similar to an allergic reaction in humans.
Although baking soda has been used since 1933 to treat plant diseases, recent research indicates that in large amounts, it may build up to toxic levels that damages or kills plants. Baking soda is not effective unless mixed with oil, which has the potential to burn plant leaves when used improperly. Commercial bicarbonate solutions, such as potassium bicarbonate or aluminum bicarbonate, may be safer and more effective. As an added benefit, these products also contain nitrogen.