Could well be - I'm no expert on plant diseases but it looks like it. However, since the pustules and black patches are on last years leaves you can safely remove all the affected foliage and burn or bag it. Info. (NB The information is for the UK where no fungicides are available to home gardeners for control. In the US there may be since controls on pesticides are different.)

It is rust and it can be a pretty serious problem. It is a systemic ailment, in that all future growth from that plant will be infected. Won't necessarily kill the plant but it does affect blooming and fruit production. It can be treated but the recommendation is to remove the plant and destroy.

Aww, that's unfortunate. Thanks for the ID, gardengal48 and floral-uk. Is there a way to avoid this in the future? Should I destroy the plant and avoid the same spot? I'm not sure how this fungal infection spreads.