For many home gardeners, one of the best parts of the summer is harvesting the juicy, bright red tomatoes that they have nurtured to ripeness. Unfortunately, a number of different tomato plant diseases have the potential to wreak havoc on backyard crops, shriveling their foliage and leaving their fruit covered in patches of mold and rot. Four of the most common tomato plant diseases are early blight, bacterial canker, blossom end rot, and anthracnose. Learning to recognize the symptoms of these diseases can help the home gardener see her plants through to harvest time.
Early blight, caused by fungus present in some soil, is one of the most common tomato plant diseases. It normally affects plant leaves and stems, which become scattered with small yellow circles that have black “bull’s eyes” at their centers. If left untreated, the plant’s leaves will begin to fall off, leaving immature fruit unprotected from the hot summer sun. Early blight damage can be minimized by treating soil with an antifungal spray, which can be purchased at gardening centers and home improvement stores.
Another disease which commonly affects tomato plant leaves is bacterial canker. This disease causes foliage to shrivel and dry on the plant’s vine, again leaving immature tomatoes unprotected from the sun. Affected plant stems may secrete a yellowish ooze. The bacteria that cause this disease may be present in the soil or may be found on tomato seeds. Gardeners can minimize bacterial destruction by purchasing tomato seeds from reputable suppliers and by treating affected soil with a spray containing copper, a natural fungicide.
Of all tomato plant diseases, blossom end rot is perhaps the most frustrating. Tomatoes plagued by this condition often appear perfectly healthy on the vine, but when they are picked it is discovered that their bases have been “eaten away,” leaving a dry, black hole where their flesh should be. This condition occurs when growing plants do not receive adequate calcium. Often this deficiency is caused by overly forceful watering, which can wash crucial nutrients away from plant roots. Gardeners can prevent this occurrence by watering gently and treating soil with nutrient-rich mulch.
Anthracnose also commonly affects tomato plants’ fruit. This disease causes round, sunken patches of rot on the fruit’s skin which grow and darken over time. It is often caused when a fungus present in the soil is splashed onto a plant's fruit during watering. Gardeners can minimize anthracnose destruction by treating soil with copper spray, trimming plants’ lower leaves so they do not come into contact with fungus-affected soil, and watering carefully to prevent splashing.