Tomato plants given proper care and a healthy, sunny environment grow shiny, firm green leaves. Plants with leaves that appear shriveled, wilted or dried up likely suffer from lack of sufficient care or a bacterial, soil-borne disease. Determine if your tomato plant is, in fact, drying up, or if another condition may be causing the plant stress.
Also called leaf curl, leaf roll causes a tomato plant's lower leaves to appear to dry up. The leaves actually curl inward around the edges, due to rainy, cool, wet weather conditions. Leaves also become thick, leathery and rough to the touch. However, leaf roll does not affect the health of the plant, and you do not need to treat the plant. When rainy, cool weather passes, the leaves straighten and shine.
Fungicides and Herbicides
Fungicides and herbicides can distort or permanently deform tomato plant leaves and fruits. Tomato plants are especially sensitive to 2,4-D fungicide, a compound similar to plant hormones. Damage from overuse of the spray bends the leaves down, causing cupping (which may appear like drying or wilting). If the exposure to the harmful spray is not too severe, tomato plants can tolerate the injury and produce healthy blooms and flowers. To offset the damage, water the plant thoroughly -- at least 1 inch of water per week -- on a regular schedule.
Over- or Under-Watering
Tomato plants require a minimum of 1 inch of water every week. For tomato plants growing in hot, humid climates, such as Texas or Arizona, watering the plant with 2 inches of water per week is ideal. Because tomatoes are made of up of 90 percent water, they require an abundant water supply to produce healthy, juicy fruits. Under-watering a plant causes leaves to dry up, and eventually the plant will die, likely without ever setting fruit. Increase watering if under-watering is likely, watering the plant every day for one week to see if symptoms go away. Water the plant directly at the roots until soil starts to pool on top. Over-watered plants exhibit similar symptoms to thirsty plants, such as shriveled leaves. Decrease watering to at least 1 inch of water per week, especially if heavy rain falls frequently in your area.
Fusarium or Verticillium Wilt
Fusarium and Verticillium wilts are both soil-borne bacterial diseases that first appear as shriveling and wilting in a tomato plant's lower leaves. Leaves then turn yellow, which usually leads to premature death. The two diseases exist in garden soils where plants susceptible to the disease grow. Horticulturists have developed disease-resistant varieties -- marked as "V," "F," or "VF" resistant. Planting these varieties are the only control. Otherwise, as of 2011, no treatment exists for the diseases. Remove the entire plant and all plant parts from the garden bed or container and plant disease-resistant plants, preferably in a new, uninfected garden.