Bacterial canker is a serious disease usually seen on plum and cherry trees, but may also be found on other Prunus species, such as apricots and peaches. The leaves develop brown spots, which may be surrounded by a yellow halo. The spotted areas then fall out, giving a 'shot-hole' appearance. Lesions (cankers) begin to form on the bark and exude a sticky gum.

Control

The disease is caused by the bacteria Pseudomonas syringae, which enters the plant through leaf scars and wounds. Control may be carried out by pruning away the affected branches between June and August, making sure that any pruning equipment is thoroughly disinfected between each cut to reduce the risk of spreading the disease. The plants may also be sprayed with copper fungicide once a month from mid-August to mid-October.