In article ,
Spider wrote:

Thanks for your response.

I would hazard a fairly intelligent guess at Phytophthora. It seems to
be made worse by winter wet, but presents symptoms in summer. I lost a
Cryptomeria to it.

If it is, it is behaving very strangely. But it may be an anomalous
reaction.

You might as well follow your instincts and cut it back, but I doubt it
will recover well given that the roots will be affected. If it is
precious, you could try deeply spiking the ground locally to improve
drainage/compaction, then using something like Rootgrow to encourage
root recovery. However, I think that will probably just be a stay of
execution rather than a miracle cure.

I think it very unlikely that the roots are seriously affected, as
this has been going on for a few years (though this was the worst
year yet), under 10% of the plant is affected at any one time, and
the rest of it is as vigorous as before.

A couple of the pictures I posted show clearly that the cause of the
leaf whitening is that the branches are dying round much of their
circumference. Phytophthora, it may be well be - but whatever it is,
it seems to be primarily a branch effect.


Regards,
Nick Maclaren.