Common Tomato Diseases

The best way to combat tomato disease is to find disease-resistant varieities. If disease develops, rotate crops and remove debris from year to year.

Alternaria (early blight): Caused by the fungus Alternia solani, this condition is characterized by tiny brown spots, which first develop on leaves, and then spread to the fruit and stems. It develops when leaves are damp for more than 48 hours.

Fusarium wilt (only affects tomatoes, likes warm soil): A soilborne fungus that causes wilt and brown discoloration in the tomato’s stem by attacking the plant’s water-carrying (vascular) system. (Note: There are two different strains of fusarium wilt – race 1 and race 2)

Nematodes: Microscopic roundworms that attack the roots of plants. Note: Not all nematodes are harmful; some eat grubs, nasty little larvae that can detroy your lawn.

Tobacco mosaic virus (aka tomato mosaic virus): Readily transmitted, the virus causes light and dark green mottled areas on the leaves, or bright yellow mottling of older leaves; also leads to stunted growth, rolled foliage, and brown fruit.

Tomato hornworms: Sphinx moth larvae; 3-1/2 to 4” long and green; leave behind green or black droppings; have five sets of “legs” and horns at their rears. They eat leaves and can be controlled by pesticides, or in small gardens, by handpicking.

Tomato spotted wilt: The most striking aspect of this virus appears on young fruit and consists of white to yellow, usually raised, concentric rings, 1/2” in diameter, on the fruit’s skin. Foliage often has a bronze cast.

Verticillium wilt: A soilborne virus that causes bottom leaves to wilt, die, and drop off. It also leads to stunted plants and small fruits, which often experience sunscald due to lack of leaf coverage.

Hybrids come with the following abbreviations; each indicates the disease to which the plant is resistant.

Tomato Disease-Resistant Abbreviations: