The disease strikes early, within four weeks of transplanting outside. I believe the culprit may be a fungus, since cold nights and damp weather in May/June seem to cause it. The recent series of cold nights in late May has cost me half my tomato plants, despite wrapping them in greenhouse plastic and keeping hotwater bottles inside.

The diseased plants look perfect and healthy, except for a brown, dry lesion on the stem right at the soil line, typically reaching up about an inch above the soil. On some plants, the lesion slices all the way up the stem in a thin streak. There is no evidence of fungus or spore-like powders in the lesion. It's as if the outer part of the stem has been chewed off or dissolved, leaving just a dried out core.

If I leave the plants, by mid June this brown dry lesion will completely collapse the stem.

This disease also appears to be very contagious. All the plants in a cage (I plant three plants to a [very large] cage) will get it if one gets it. Yet plants in the next cage might not (keeping in mind that they are currently wrapped in greenhouse plastic, which isolates one cage from another).

When I pull up the diseased plants, I can see healthy roots and healthy leaves. When I cut the stem, I see healthy green tissue inside. I don't see any of the reddish brown, grey, or other streaks that are in the tomato disease photos on the web.

The heritage tomatoes seem to be more susceptible than the hybrids (Celebrity seems to have the most resistance).

I am experimenting with trying to save two of these plants, simply because these are my last seeds. I have painted the stem above the dry lesion with rooting hormone. Then I have placed a large tin can around the stem and filled it with clean potting soil. I am hoping the tomato can root above the lesion and keep itself alive till I get some seeds.

Any ideas what this disease might be?

Wishing for warmer spring...

The plants in question were quite tall -- about 40 cm. I grow all my own seedlings so that they're very robust when I put them out. I'd thought of cutworms, but the plants are far too big, and I don't know of any insects that feed on the stem of tomatoes. Besides, that wouldn't explain the dry streaks running up the stem.

As for the rerooting, I can't cut off the part with the lesion, otherwise I'd be cutting off the roots entirely. The plants will have to reroot above the lesion before it completely dries through. They're not looking very good today, I don't expect them to make it.

Where is the tomato forum?

Tomato Photos

tj