Re: Help: Pittosporum die-off
- Subject: Re: Help: Pittosporum die-off
- From: T* &* M* R*
- Date: Wed, 26 Sep 2001 11:34:34 +1200
Marina & Anthony Green wrote:
>
> Every now and then over the last few years I have lost the odd Pittosporum tobira, often the weaker
> plants in a place I wasn't too worried about them - the garden must have over 200 of the things and I
> try not to let them dominate.
> But now I am starting to get a bit concerned, as I think we have an animal eating away at the roots.
> It tends to happen on the end of a row, and when I pull out the dead stump, virtually devoid of any
> root fibre, the next P. tobira in line is often affected, and it has now spread to the clumps of
> Pittosporum which I have grown rather fond of, with just the one slightly weaker plant seeming to
> suffer in each clump.
> They are relatively free of parasites above ground - whereas when they were unpruned when I first
> arrived there were white "cocciniglia" galore, so I don't think they are to blame.
> Any ideas? Solutions?
Anthony
While a pest attack is I suppose a possibility, your description ofthe
dieback's slow spread to adjacent plants to me sounds much more like a
soil-dwelling fungus, quite possibly at a guess a species of
Phytophthora.
With such a problem digging up a completely dead plant will tell you
little - whatever the agent it will have most likely fed and gone. What
you really need to do is to examine a plant on which the trouble has
only recently started. As it is likely to die anyway you probaly should
dig it up, keeping as much of the root system as possible. Certainly see
if any insect or other animal is associated with the damaged roots, but
more importantly look for rot in roots and especially for any sign of
collar rot (ie rotting or a canker) in the crown tissue. which will
probably indicate a fungal attack.
When you have this information a proper diagnosis may be possible,
though whether any of us can thsn suggest a remedy is fairly
problematical, especially if it is a fungus which is invilved. Many of
these soil-dwelling fungi are very hard to deal with..
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, New Zealand, SW Pacific. 12 hours ahead of Greenwich Time
