I have been growing several pots of boston ivy for 4-5 years on my roof patio wall and each year they develop some type of leaf wilting fungus as soon as it gets above 80-85 degrees / first noticeable humidity (around June 1st). I have looked at all the pictures of leaf spots, powdery mildew, etc but cannot figure out what it is. I have used copper spray, neem oil, etc but can't seem to stop it and by late summer I've removed about 50% of the leaves due to fungus. Does anyone know what this is and how I can stop it?? It seems to develop from the edges and decays the area to appear almost translucent (see picture). It seems to overwinter since it comes back each year same time and affects all of my vines. Any help would be MUCH appreciated!!!