We live the Bloor Dufferin area of downtown Toronto and have a 20 year old siberian crabapple in our back yard. Each spring, it looks very healthy with new growth, lots of flowers, and very happy looking leaves. Then come every July, large portions of it seems to die-off, Large sections of its leaves turn brown then fall off leaving large bald spots that remain until the following spring when it becomes fully covered with leaves and flowers again. It happens every year!
Is this normal for siberian crabapple? Is there something I should be doing?
Thanks for contacting Toronto Master Gardeners. It is unfortunate that this is happening to your lovely tree. Without a picture a definitive diagnosis can’t be made, but, from your description it sounds like your tree is infected with fire blight bacteria (Erwinia amylovora). With this disease the ends of twigs and branches become brown or black and may curl into a shepherd’s crook shape. Cankers formed during the previous season may ooze a cloudy liquid during wet spring weather. Most cankers are small and inconspicuous so the infection might not be noticed until flowers, shoots, and/or young fruit shrivel and blacken.
These guidelines describe how to best manage the infection. To restore your crab-apple to health, it is crucial to monitor the tree regularly and remove and destroy the blight infection through careful pruning at the appropriate times. You might also consider hiring professional arborist for assessment and treatment of the tree. Contact Landscape Ontario for a list of qualified arborists.
Good luck with your tree.