Hi all. Back in April, I bought a Nagasaki Crabapple from someone from my local club. It was very healthy then, with flowers just finishing up. However, in early-mid June, I noticed that the leaves were browning and curling up. I was quite confused as I'd never encountered this before, but then I deduced that it was probably a disease that had come from an apple tree in our garden which had been moved previously, most likely weakened. I then posted on Reddit asking for advice and to see if anyone could identify the specific problem the crabapple was facing, however no one could answer it definitively and someone said that it was from too much direct sunlight and lack of water. I didn't think this could be the case as the previous seller (who is very reputable and trusted) had the bonsai in direct sunlight constantly in a south-facing garden, and it was completely fine with him. I was making sure to give it plenty of water, soaking it twice thoroughly on my watering runs.
I'm possibly thinking that it's 'Apple Scab', however this is my first time facing a disease / fungus (or whatever it is) on my bonsai apart from powdery mildew or a general aphid infestation. I sprayed it with some rose rust spray when this problem was happening, and it didn't seem to improve. If anyone's seen this before, I would appreciate it if someone could identify it for me. Any advice on the next steps I should take to nurse it back to health would also be appreciated, as I was told that I should give it a thorough wipe down with lime sulfur in the winter to kill any fungus on the tree before it wakes up in spring. If you need any more pictures to help identify it, please request them.
I'm possibly thinking that it's 'Apple Scab', however this is my first time facing a disease / fungus (or whatever it is) on my bonsai apart from powdery mildew or a general aphid infestation. I sprayed it with some rose rust spray when this problem was happening, and it didn't seem to improve. If anyone's seen this before, I would appreciate it if someone could identify it for me. Any advice on the next steps I should take to nurse it back to health would also be appreciated, as I was told that I should give it a thorough wipe down with lime sulfur in the winter to kill any fungus on the tree before it wakes up in spring. If you need any more pictures to help identify it, please request them.