Yes Michael - the 'soft' Irish climate can be a bit a problem with fungus attacks. In the South West in particular where it seems to rain every five seconds.
However, in my garden, rust seems to be only an occasional problem with PM a bit more common but blackspot is a constant battle. I find I have to give - at a minimum - a monthly spray with myclobutanil or some other fungicide from May or many of my roses will be reduced to near bare canes by mid July.
I am also a bit surprised that Tess doesn't seem to warrant the attention that other Austins get given its overall vigour and profusion of vibrant crimson blooms.
Q