Tobacco mosaic, a highly contagious virus, spreads to tomato plants by people who’ve handled tobacco, including smokers and tobacco chewers. Malformed or mottled leaves are symptoms of mosaic. Bacterial canker, which causes drying of leaves, open lesions on stem surfaces and crop loss, may have also been the culprit. Dead leaves usually remain attached, and damage often occurs on only one side of the plant. A third possibility is fusarium wilt, which causes the leaves to turn yellow and fall off. A section of stem, cut near the plant’s base, will show a brown discoloration of interior tissue.
To prevent the spread of tobacco mosaic, wash your hands thoroughly before you handle plants. (Why not quit smoking, too? ) It’s good practice to remove any diseased plants and those surrounding them, and burn the vines. Eliminate perennial weeds and keep tomatoes away from tobacco, cucumbers, potatoes and other possible disease carriers. Rotation of crops will help prevent buildups of any of these diseases.