In article ,
Jeff Layman wrote:
On 04/10/2020 10:22, Nick Maclaren wrote:
In article ,
Jon Nicoll wrote:
I'm trying to determine why our viburnam has died, in somewhat
spectacular fashion

The symptoms are wildly unlike either honey fungus or phytophthora, and the
Web and media do us no service by banging on about those.

I am afraid a comment the OP made - and I missed at first reading -
/does/ suggest Phytophthora. He stated "There are deep cracks running up
one or two the trunks".

But phytophthora attacks only living tissue, and spongy heartwood
is an almost certain indicator of fungal attack. The vigorous shoot
also argues against phytophthora, because that generally kills first
and subsequent fungal attack destroys the dead plant.

Verticillium and other fungi can also cause deep cracks in bark,
incidentally. I have a Cotinus coggryia with all of its stems down
to the heartwood for half their circumference, and it has been like
that for many years (it's Verticillium).


Regards,
Nick Maclaren.