If you can get fungal-based compost tea, that should work well, but the tea needs to be brewing when you buy it. I had rust on my quince and serviceberries really bad and it took care of it. I make it, but you probably can buy it somewhere near there. There's also an expensive one that you can buy. I think it's called like Serenity? A very good gardener told me it killed his fungal disease. If someone out there remembers what it's called please chime in.
John S
PDX OR