Posted: 09/08/2014 at 17:26
I presume you prepared the soil before planting by changing part of it, or at least using Rootgrow to encourage growth?
If so, it sounds like you have a very bad case of blackspot.
You need to spray regularly to keep this under control, not just when you see it.
Next year, you want to start spraying just as the leaves open, and then as often as your chosen product recommends.
For the moment, pick up any fallen leaves and make sure the plant is well-watered.
Have a read of this, too: