Over the past few years I have noticed my autumn flowering cherries have started to look worse each year. The leaves are full of holes and the small twigs are all dead. Do you know what could be causing this and is there any cure?
If it is any consolation, you are not alone. Our research laboratory has received many phone calls regarding this problem. Your trees are under attack from a bacterium known as Pseudomonas syringae, the casual agent of bacterial cherry canker. All autumn flowering species of cherry are highly susceptible to attack from these bacteria. Symptoms include tattered leaves which form the distinctive shot hole symptoms, cankers on trunks, limbs and branches exude gum during late spring and summer while leaves on the terminal portions of cankered limbs and branches may wilt and die in summer or early autumn if girdled by a canker. Control is as follows. Pruning should be carried out in the summer during dry weather, as infection of the branches occurs in autumn and winter. Cankered limbs should be pruned well below any visible cankers with sterilised pruning tools. Foliage can be sprayed with liquid copper oxychloride in September, October and November to protect leaf scars from infection. In addition we also recommend trying to improve tree vitality by appropriate fertilising, mulching and watering during spring and summer.
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