Why Do Leaves on Tomato Vines Turn Brown & Dry Up?

Fusarium Crown Rot

• Fusarium crown rot, which is caused by the fungus Fusarium oxysporum, results in brown or black, wilted leaves. Discolored roots and cankers at the base of affected stems verify that fusarium crown rot is likely the problem. Planting resistant varieties helps prevent the disease, but there is no cure. Resistant tomato seeds and plants are labeled with codes such as VFN or VFNT. The "F" in the code indicates resistant to fusarium wilt.

Verticilium Wilt

• Caused by the soilborne fungus Verticilliurn albo-atrum, verticillium wilt thrives in cool soil like that found in the Northeast. Beginning at the bottom of the plant and working its way up, the leaves first turn yellow, then brown, and then drop off. Symptoms often occur only after the plant begins bearing fruit. The fruit that matures, although small, is safe to eat. The disease remains viable in the soil for 4 or 5 years and multiplies in many types of weeds even when no tomatoes are in the area. A "V" on the disease resistance code indicates resistance to verticillium wilt.

Bacterial Canker

• Bacterial canker's first symptoms are downward-turned leaves followed by brown streaks. Symptoms begin on lower stems and gradually travel up the plant. The streaks eventually extend to the leaf stem where a canker forms. The fruit is small with scabby, white lesions called bird's eyes. Destroy the plants with these symptoms. The disease spreads through seeds, so don't save the seeds from plants suspected of having bacterial canker.

Management

• Plant diseases that cause brown leaves are incurable, so practice preventative measures. Tomatoes, potatoes and eggplants are members of the nightshade family. Wait at least 3 years before planting tomatoes in an area where a member of the nightshade family previously grew. If you suspect your tomatoes have verticillium wilt, wait 5 years before planting another susceptible crop. Keep the garden clean and free of plant debris and weeds and allow plenty of space between plants so that air freely circulates.

Cultural Considerations

• Tomato plants need 1 inch of water in the form of rainfall or irrigation each week in mild climates. In hot climates, they need as much as 2 inches of water. Prolonged dry spells cause yellow leaves that may eventually turn brown. Too much water may smother the roots, which causes symptoms similar to drought. Cultivating more than 2 inches deep near the plant may damage the roots so that they can't take up adequate water. Severe overfertilizing burns the plants, causing dry, brown leaves. Avoid high nitrogen fertilizers. A pound of 5-10-10 fertilizer is sufficient for 20 plants.