Tried both white and eco oils over two years (homemade and bought). Suspect both house paint and soil are infected. No sign of any scale, insects or the like. If it can't stop it will have to remove the many bushes :(
13 August 2021 03:06 PM
From looking at the photos there seems to be some pest activity on the stems and under the leaves. It may be mites that are causing this issue, which are sometimes harder to locate until they are in larger numbers.
As it is persistent, we recommend applying Yates Natures Way Citrus & Ornamental Spray. This product has the pest control and sooty mould coverage in one.
We would also recommend giving the Gardenias a good feed to assist with overall health and recovery. An all round fertiliser like Thrive Naturals Roses and Flowers Concentrate, will provide the nutrients the Gardenias need as well as assisting with recovery.