Just noticed this on my store bought plant (not grown from seed). It's now fruiting, and I don't see any white spots on the leaves.

original stem

Update: 25 Feb 2016 with close up of the stems and an more distant view of the plant health

close up of affected stems

plant health

  • Installed imgur app so I can upload an image, but doesn't seem to be working – Graham Chiu Jan 17 '16 at 9:48
  • No need to install an app to upload the image, but I see it fine. – jeremy Jan 18 '16 at 0:43
  • I can't see a way to upload an image from an android device. So had to find a free web service, which meant installing another app. – Graham Chiu Jan 18 '16 at 1:22
  • Ah, okay. I understand – jeremy Jan 18 '16 at 4:13
  • Are you referring to the patchy ghosting on the lower stem? – J. Musser Feb 10 '16 at 2:37

That appears to be Southern Blight, Sclerotium rolfsii

It's a fungal disease from the soil, and affects many species of plants. You cannot cure plants infected with it. From the University of California:

  • Rotate to nonhost crops, such as corn, sorghum, rice, or small grains, for at least 2 years to reduce inoculum.
  • Deep plowing to bury plant refuse may help to destroy sclerotia.
  • Keeping the tops of beds dry in tomato fields helps reduce the disease in furrow- and buried-drip-irrigated fields.

For potted plants, I'd recommend disposing of the potting medium, and sterilizing or disposing of the container.

enter image description here

  • "tomato plants with southern blight have lesions on the stem at or near the soil line. These lesions develop rapidly, girdling the stem and resulting in a sudden and permanent wilting of the plant. White mats of mycelia are produced on the stem and in the adjacent soil. In a few days, tan to brown spherical sclerotia about 0.06 inch (0.5 mm) in diameter appear on the mycelial mat. The abundant sclerotia are a good diagnostic feature." I'm not seeing a white mycelium mat on the soil, no sclerotia, and no wilting though the leaves are slightly curled. – Graham Chiu Feb 11 '16 at 4:47
  • @GrahamChiu you're right.. I didn't see your picture well from my phone. Do you mind getting a closeup of the affected area? – J. Musser Feb 13 '16 at 23:47
  • I'm back at home so can provide the closer image – Graham Chiu Feb 25 '16 at 7:30
  • The plant survived to the end of summer/early autumn and I got a few tomatoes off it. But it succumbed to scale attack. – Graham Chiu Jan 15 '17 at 22:21

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