My Serviceberry has a bad case of rust. Or, is it more than that? Can I treat it? This tree is 4 years old. The 1st 3 years it produced berries that the birds fought over. Last year the rust was mild (that year my neighbor planted a rusted' plant within 200' of this one) but this year it is very bad and the lower leaves are affected as well. Can I save this tree? It is in partial shade, medium wet soil and otherwise looks fine (trunk and new growth). Thank you.