Tomato stem rot

[MelanieSW]

Today I discovered that the stem on one of my Bloody Butcher tomatoes had completely rotted halfway up the plant. It has basically collapsed. Presumably a fungus, though it doesn't quite look like late blight, and it would be rather early for that.

Googling brought up Didymella stem rot, is someone able to confirm this diagnosis? It's not something I've come across.

Plant has been pulled and disposed of, and so far the others don't appear affected.

[ameno]

To be honest, I'd say that looks a lot like blight, if it weren't for the fact that none of the leaves seem infected. It doesn't make any sense for the stem to be so badly infected that it snaps before the leaves even show anything at all.

[MelanieSW]

To be honest, I'd say that looks a lot like blight, if it weren't for the fact that none of the leaves seem infected. It doesn't make any sense for the stem to be so badly infected that it snaps before the leaves even show anything at all.

Yes it's really weird. The rest of the plant looked so healthy that I was almost tempted to just cut off below the affected stem and train up a side branch...

I've had blight occasionally before, but never before August. And then the stems never rotted so badly so quickly that they just snapped before I could bin them.

[Snoop Puss]

I'm no expert on these matters, but might it be blackleg? I remember it being mentioned here a long time ago as affecting someone's tomato plants.

[ameno]

I'm no expert on these matters, but might it be blackleg? I remember it being mentioned here a long time ago as affecting someone's tomato plants.

I don't know whether blackleg affects tomato plants or not, but if it does it would be at soil level like in potatoes, as it needs the extra humidity it would get down there.

[Snoop Puss]

Some info and pictures here (from the States): https://ipm.ifas.ufl.edu/pdfs/Pythium.pdf

[MelanieSW]

Thank you both for your replies. Luckily so far none of the other tomatoes has been affected.

I'm still not entirely sure what it was, though Pythium myriotylum sounds like a possibility as it apparently can attack stems further up in humid and wet conditions.

Talking to other plot holders the best guess is that the pot for potting on wasn't cleaned properly. This is entirely possible - for next year I'll better clean them now rather than doing it impatiently on potting-on day....