it is quite interesting to try homoeopathy with plants. not an exact science, but there are good pointers if you look for example at:

what time of year the plant is affected - what type of weather/ climate conditions aggravate?

what is the nature of the problem - what type of discolouration for example? what if any smell from the fungus/ sappy discharge/ infestation?

something i have tried which is not homoeopathic, but might be of interest is a little experiment on a witch hazel in my garden [from which i live a long way at present, so i have not been able to check if it works.] the tree sits in chalky soil which is of course bad for an ericaceous plant - it gets by there without thriving.
last year i put some calc carb around it, to see if that would attenuate the maintaining cause of the wrong soil. i haven't been able to check on it yet, but i hope it might save some digging out and soil-changing. if it works then one might get around restrictions of soil ph much more easily than the usual hard work method.