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Hi ,can anyone tell me what is causing the black sootlike stuff on my rhododendrons,azaleas and pieris please and what can I do about it,they look a right mess ,never seen it on them before

Adam Pasco

I wonder if this is sooty mould, although I've never seen it on my rhodo, azalea or pieris before, but have had it on my camellia.

Sooty mould develops on the surface of leaves when sap, or honeydew, drips down onto the surface from sap-sucking insects above. Scale insect is the usual culprit. 

Sheddy, take a look at the underside of the leaves above the sooty ones and see if you can find scale insects feeding. If you have then you'll need to try and get rid of these pests in some way (not easy), but if not we'll have to think again. Let us know what you find.

Alina W

It can also be caused by honeydew dripping from overhanging trees. If this is the case, all you can really do is wait for fresh leaves on the bushes. Although it's ugly, it won't do your plants permanent harm.

Adam Pasco

Oh yes, and you can wash it off – although not sure you'll be able to use a hose pipe for teh job! I can't in my area. If the rain has softened the black coating try sponging it off, or fill a pressure washer with water and try getting spraying it away.

On my camellia I just went over teh bush with a bucket of water and a sponge, and this did the trick.

I have the same problem with my pieris and it is so bad that the 'black soot' was all over the plant pot and stems.  I was told to spray the plant with water and bicarbonate of soda.  It has has one blast so far and the black is starting to wash away? watch this space


Watching this space michizzle - any follow-up?

I have the same problem right now with a Pieris and Rhodadendrum side by side, both are covered in this black soot, especially on the older, longer leaves.  Those of the Rhody are drooping badly and turning yellow, just when the bush is attempting to be in full flower. 

An adjacent climbing rose tree also seems to have died suddenly, after giving a great display last year, and I'm wondering if it could be a honey fungus problem.




I have the same problem on my azalea and pieris this year. Never had it before, and was wondering what to do. I will try your remedies. I have loads of buds but it looks as if they are not going to open!

This 'soot' is all over an old established jasmine which covers the house up to the roof in one area. so washing the leaves is out ! It's also, though not so badly, affecting my row of large (4'+) potted camellias. Help!



Thanks will try this as I have got nothing to loose.

I has this black "mould" all over my pieris but I can't find any evidence of insects or honeydew either on the plant itself over from adjacent I treat it in the same way. Tia

Last year tried the above cleaning method on my rhododendron and it unfortunately didn't work, so I had to cut it right back. It was over six feet tall and it still hasn't recovered. It spread to my nearby plants, including choisa and this year it has attacked more plants the other side of the garden, including a large pieris, which has turned black.  It is also affecting my camellias.  I have sprayed them both this year and last with bug killer, and that hasn't worked either.  HELP!!!

I have it on a large pieris is and also adjacent rhododendron (although not too affected). The whole bush - upper and underside of all leaves  branches thickly coated in soot mould. Tried wiping off - failed as too many leaves and treated with mildew killer. Nothing has worked. Will try above suggestions but I'm of the mind now to cut it down to the ground.








Zigga, spraying will do no good. ,

the cause is aphids.  Their secretions help sooty mould to form

bit of a job but you meed to physically wash as many leaves as you can THEN you can spray with an insecticide

i had a choisya, skimmia and sarcoccoca covered with mould ....maybe 4 years ago.  Every leaf, just about, was washed top and bottom.  i lightly pruned back all bushes to start with then used an insecticide. a soap spray a couple or more times during the summer comtrolled further aphid attacks.

my bushes have been clear ever since

cheshire gal,  a mildew killer will have no affect but try pruning back to a more manageable size to again attempt to wash your rhodo. 

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