My tomato plants are healthy looking and a good size but the lower 20% of the plant has yellow leaves that turn brown. Can you suggest anything as to cause and cure?
The Gardener’s Answer
Hello, Hoyt: When tomatoes have the symptoms you have described, such as the lower foliage on plants turning yellow then brown, the most common problem is a fungal disease known as either early or late blight. This disease starts on the lower leaves and then works its way up the plant. You would first notice dark spots on the foliage. Severe cases can destroy plants but if noticed early you can prevent future spread by removing the affected foliage and mulching around the plants to help stop the spores from splashing up. This problem is common during periods of excessive rainfall. Maintaining proper fertility is also important in controlling this problem. Nitrogen deficiency has similar symptoms without the dark rings. Solving this problem is as easy as spraying the foliage with a general purpose fertilizer such as fish emulsion. Then apply a granular slow-release fertilizer to maintain a healthy nutrient level. Good drainage is important as well.