What are the Different Tomato Plant Diseases?

Dee S.

Tomatoes are one of the most popular menu items in homes and restaurants across the world. Used in salads, sauces, soups, and stews, the possibilities are endless for a ripe, juicy tomato. Unfortunately, the tomato plant is susceptible to many diseases. Tomato plant diseases account for the death and destructions of many crops both in gardens and greenhouses every year.

A number of diseases can damage tomato plants.
A number of diseases can damage tomato plants.

One of the most common tomato plant diseases is septoria leaf spot. It is the work of a fungus, Septoria lycopersici. Gardeners may first notice small spots on the plant leaves that eventually grow to approximately 1/8 inch (.3 cm) in diameter. Next, lesions develop on the leaves that are typically gray in color with darker coloring around the lesion edges. This pattern is the easiest way to determine whether the plant has septoria leaf spot.

Tomato plant diseases cause the death and destruction of tomato crops in gardens and greenhouses every year.
Tomato plant diseases cause the death and destruction of tomato crops in gardens and greenhouses every year.

The fungus associated with septoria leaf spot is spread from leaf to leaf when the rain splashes and spreads the spores. Once the leaves are infected, they turn yellow and die. To control it, gardeners should leave enough space between plants so that the fungus cannot pass from plant to plant. Also, water the plants in the morning near the base, thereby giving the leaves a chance to dry during the day. Fungicides can also be used to control septoria leaf spot.

Another of the many tomato plant diseases is early blight or target spot. Target spot is the caused by Alternaria solani, a fungus. Gardeners can usually tell if their plants are affected by target spot if they lose their bottom-most leaves prematurely or if they notice black or brown spots with darkly colored edges on the leaves. Another telltale sign is the target-looking appearance of the rings that form on the spots. Luckily, it too can be treated with fungicides and there are some tomato varieties that are resistant to the fungus.

Two kinds of fungus cause wilt: Fusarium axysporum and Verticillium albo-atrum. With these tomato plant diseases, the plants have yellow and wilting leaves. The plants usually die prematurely and often have infected stems with the first variety of fungus. With the later variety, the plants will be stunted, but they can survive. The same control measures that are used for septroia leaf spot can be used for these fungi.

Bacteria can also cause tomato plant diseases. A few of the most common include bacterial spot, bacterial speck, and bacterial canker. With bacterial spot, yellowish spots appear on the leaves and stem, leaving them greasy to the touch. Bacterial speck has darker spots with a yellowish halo. Bacterial canker is the most severe of the three destroying leaves and fruit. Fortunately, the bacteria can be treated with a spray infused with copper.

There are hundreds more tomato plant diseases Each region is affected by a particular mold, fungus, bacteria, or even virus. A local nursery will be the best way to determine the kind of disease and to instruct the gardener on the best way to treat it.

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