We have a 10-yr old pyracantha (screen hedge). It has always been vigorous with loads of flowers and berries. This year it suffered massive leaf drop, leaves yellowing before drop. There is some regrowth, but struggling with few flowers. All the leaves are very pale green and many even have cream/white colored edges and tips. All the leaves are curled inwards. There is no sign of any infestation. Two other pyracanthas alongside this ailing one have no problems at all! I am at a loss as to what is going on.
Certified GKH Gardening Expert
It sounds like it could be scab. This article will help: