black soot on pittosporum??

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philistine Melbourne, Australia Apr 05, 2012

HI all!

Ive been trying to save a large, well established Pittosporum tenuifolium hedge which has been seriously suffering from what seems to be black sooty mould. ITs all over the leave, the wood and even the trunk of the worst affected plant.
I've been monitoring over the last few months, but it just seems to keep getting worse and has actually killed a section leaving what looks like burnt bare wood.

When I first noticed it, months ago, i checked it thoroughly for signs of aphids or whitefly or anything really, but never noticed anything. I treated with a white oil/pyrethrum combo anyway but the fungus just seemed to get progressively worse.
I've also been keeping the surrounding soil free of any of the fallen diseased leaves as much as I can, but the hedge belongs to a client of mine who I only visit fortnightly

I've also recently attempted to treat with a fungicide (mancozeb/sulphur) giving it an allover spray - including soil - once every fortnight for 6 weeks, but it still looks like its getting worse.
I 'm wondering, would a copper based spray be any more effective?
Is it a lost cause?
Any suggestions at all?

Thanks in advance!

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ecrane3 Dublin, CA(Zone 9a) Apr 05, 2012

Have you checked the stems carefully for scale? I've never seen sooty mold unless there's been some sort of sucking insect that secretes honeydew around. The sooty mold grows on the honeydew not actually on the plant so if it really is sooty mold then there pretty much has to be something around that's producing the honeydew for it to grow on. Are there trees or anything else growing above the pittosporum hedge? I observed once someone had a crape myrtle tree that was infested with aphids, and the honeydew had dripped down onto plants growing below it and so they got sooty mold even though the aphids weren't on those plants.

It might also help if you could post some pictures in case it's something other than sooty mold.

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