If there is a water-logging at the foot of the tree, make sure to devise a proper drainage system for the same. Understanding these diseases and how to treat them can help protect plum crops and allow them to thrive for years. We never pruned it till about 2 year ago when we cut off a lot of branches - our neighbors were complaining that it was spreading into their backyard. This is because trees decay from their center towards the outer edge. Copyright © Gardenerdy & Buzzle.com, Inc.