In article ,
David Hill wrote:

It isn't just pak choi, but I have seen it in chard and other things.
Quite a lot develop long brown streaks in the stems, which look like
some form of rot, mostly on older leaves. What I don't know is what
triggers it.

I have flea beetle, but I don't think that's it, as I can see no
association with physical damage.

Any ideas?

I remember growing Chinese cabbage a few years ago, some of them got a
stem rot which sounds almost the same. I was told it was Boron deficiency.

Yes, the pundits quote that as a mantra, but there is no evidence
for it, and I am pretty sure that it is not the case with me. Inter
alia, one would expect far more uniformity across plants than I am
observing.

With the price of boron I'd water some on, you are talking parts per
million.

Been there - done that.


Regards,
Nick Maclaren.