When your tomato plants wilt, the cause may be as simple as poor watering habits or as devastating as bacterial disease. Wilt is recognized as the leaves on the plant dropping downward and the stems appearing rubbery and pliable. The leaves may also be yellowing and curling at the edges. The main stem or stalk of the tomato plant may also wilt, causing the top of the plant to slump.
A lack of water may be causing your tomato plants to wilt. Tomato plants need approximately 1 inch of water each week to remain healthy. If your plants perk up after watering, a lack of moisture in the soil could be the cause of the wilt.
Over-watering your tomato plants may also cause wilt. Tomatoes react badly to "wet feet," a condition that refers to their roots being trapped in wet soil for extended periods of time.
Consistent watering at a constant depth may restore the health of your tomato plants. If the problem lies elsewhere, though, your plants will continue to wilt despite your good watering habits.
Tomato plants that exhibit wilting and browning leaves on the lower branches may be suffering from a fungal infection known as Fusarium wilt. The tomato plant may also show the symptoms on just one side or on a few individual stems or branches. The wilting and browning, however, usually starts on the lower branches.
The fungus is soilborne and enters the plant through the feeder roots. This allows the disease to make its way into the plant's feeding vessels, essentially starving the plant of nutrients. To confirm Fusarium wilt, cut a small section in the main stem of the plant near the soil line and peel back the outer layer. If you see brown discolorations in the interior, your plant has Fusarium Wilt.
Remove all plants from the area and dispose of them. Sterilize the soil either through solarization or use of a fungicide. Allow the area to rest before amending the soil and adding plants.
Bacterial wilt is also a soilborne disease, but is caused by a bacterial infection rather than a fungal disease. The bacteria enter through damaged or weakened root systems--which may have been damaged during transplanting or from parasitic nematodes.
Along with wilting leaves and softened branches, you may see canker lesions on the stalk near the base of the plant. To ascertain if the condition is bacterial wilt, cut a small branch from the stalk and place the cut end in water. If you see a milky film ooze from the cut, the cause of the wilt is bacterial.
Remove all infected plants and sterilize the soil through solarization. Allow the area to rest for several weeks before amending the soil and planting.