Even though I water my garden, one of my tomato plants is wilting. What could be wrong?

A vascular wilt may be responsible for the wilting of the tomato plant.  The initial symptoms of Verticillium and Fusarium wilts are wilting of the plant leaves during the heat of the day.  Affected plants often recover in the evening or overnight.  Gradually, however, the wilting becomes progressively worse and many plants eventually die. 

Verticillium and Fusarium wilt are caused by soil-borne fungi that invade tomato plants through injured roots.  The fungi spread into the water-conducting tissue (xylem) in the stem and block the flow of water to the foliage.  Foliage of affected plants turns yellow, then wilts and dies.  A cut through the lower stem of a dead plant often reveals a brownish discoloration of the vascular tissue. 

There is nothing that can be done for plants that have Verticillium or Fusarium wilt.  Plants that die should be removed and destroyed.  Crop rotation is of limited value as the vascular wilt fungi may survive in the soil for several years.  The use of resistant varieties is the most practical way for home gardeners to prevent losses due to wilts.  Resistant varieties may become infected but many plants survive and produce an acceptable crop.  Resistant varieties are available in seed catalogs and at garden centers.

The letters V and F following the variety name denote varieties that are resistant to Verticillium and Fusarium wilts.  Wilt resistant tomato varieties that perform well in Iowa:

• ‘Jetstar’
• ‘Better Boy'
• ‘Celebrity’