I have a line of 4 Aronia arbutifolia 'Brilliantissima' plants that I love for their gorgeous fall color, carefree health, and fruit (we use a Finnish steam-juicer to make trouble-free, no-stem-removing-needed juice out of the berries, which we mix with apple juice) ... but last year the berries were not as numerous as in years past.

The only pruning I've done with these plants has been pretty minor, trying to keep them at a height of about 6 feet and not letting them get too wide (because I have a raised bed garden nearby). The main stems are now about an inch to an inch and a half wide, with just a couple of newer, much more narrow stems coming up - which I leave or pull out, depending on whether on not they'll be in the way...

Should I be doing any more pruning than this? The plants are very healthy looking; any idea why fruit production was down this past summer? (We still got enough to make a couple gallons of juice, but the yield was nothing like the year before.)