Advice on Treating Sooty Mould on a Camellia?

My Camellia 'Donation' flowered beautifully this year, but I see that many of the leaves are heavily covered with sooty mould. I'm concerned because it is in a pretty shady spot and I figure it needs all its leaves to photosynthesize. I've never noticed aphids on the camellia and this years new leaves don't feel sticky (yet), but it is under a large (rather unhealthy) flowering cherry, which could be a honeydew source. The adjacent rhododendron also has a few leaves with sooty mould.

I tried scrubbing the mould off with a toothbrush and warm soapy water, but that stuff really clings to the leaves - it took me about 10 minutes to clean a dozen leaves. Admittedly it has been sunny for a few days so the mould may have been especially dried out, but surely there is a better way.

• Am I really going to have to hand scrub each leaf?
• Should I spray the whole plant with plain water and leave it to sit for an hour or two bit before attempting a cleaning?
• Should I be using something other than soapy water?
• Once I get it clean, how can I keep it that way?

 

Hi @dt-van, I saw this posting and thought I would answer as I have suffered this problem as you have.
My remedie is baking soda and dish soap.( not detergent). I add 1 table spoon of BS and 1 tea spoon of the soap in a gallon of water and mix well. I wipe it over all leaves leaving it on for 45 minutes to an hour, then wash off with 'rain' water. I'm afraid it is laborious but it has always worked 'for me'. Friends have used neem oil with a high degree of success. But the method is the same in principle after application wait until the leaves are dry then wash off. Again I reccomend rain water for this if possible as there are no added chemicals. Friends have used a hose to ensure enough power to remove the problem.

Hope that's of some help to you.