Wilting and eventually death

Q. I'm stuck between thinking the wilting and death to my tomato plants may be pith necrosis or walnut wilt. There is an abundance of walnuts nearby and the garden plot previously had walnut saplings growing in it. However, as far as I can tell the pith is not brown or black, but instead the stems are hollow and whatever pith is left is white. The problem began with wilting at a more mature stage. It progresses to yellowing leaves then death. Now, the disease has now gone on to hit my eggplants. I would have to pull out about 30 tomato plants if it is a bacterial infection! Can you tell me what this problem is?

A. There are several possible culprits that can cause wilting, yellowing leaves, death, and affect both tomatoes and eggplants (among other crops).

• Verticillium wilt. Yellowing appears on lower leaves first, most often in a V-shape. Plant may wilt during the day and recover at night. Interior of the stem shows discolored streaks about 10-12 inches above the soil line. Affected plants may survive. If not, they're stunted. Eggplant, okra, pepper, potato, strawberries, and 200+ other plants are also susceptible to verticillium wilt.
  
• Walnut wilt. Yellowing leaves, wilting, streaking on the stem, and death - along with susceptibility in eggplant - are all symptoms of walnut wilt. It's often confused with verticillium wilt and fusarium wilt. The differentiating factor is often the fact that plants are situated near walnut trees or in an area where walnut trees were previously grown.
  
• Tomato pith necrosis. Leaves yellow, followed by wilting. The plant's main stem streaks. Sometimes it splits. A tip-off to identify tomato pith necrosis: cut off an infected stem, cut it long-wise, and check to see if stem interior is chambered (ladder-like).
  
• Bacterial wilt. Affected plants wilt suddenly. Yellowing leaves follow. The interior of the main stem becomes discolored, water-soaked, and eventually hollow. Eggplants can be affected, too. You can confirm bacterial wilt by placing a cut stem in water and check for milky ooze pouring out the end.