I have a quite old cherry tree at back yard of my newly-bought home in Scarborough, ON. This tree looks very dangerous. It already had several dead brunches being cut. And at the bottom of the trunk I can see many sawdust-like stuff coming out from the tree. Could anybody tell me what happened on my tree ? and what to do? Thank you.
The powdery sawdust you are holding in your hand is called Frass, and is produced by wood boring insects. If your tree has been infested with borers over several years, it may be too late to save it. Depending on the size of the tree and the extent of damage from these insects, you may wish to have your tree assessed by an arborist. An arborist can advise you on possible treatment options, like using synthetic pheromones to disrupt mating patterns, to control infestations.
If your tree looks unsafe, after years of pruning and damage from wood boring, you may find it more economical to remove it and replace it. Private property Tree bylaws in Toronto require a permit to remove or prune a tree if the trunk is larger than 30cm (12 inches) in diameter at chest height. You can find the permit applications on the City of Toronto website, or your arborist would be able to submit it on your behalf.
Cherry tree wood borers rarely attack healthy trees, so it is likely that the Cherry you acquired with your new home was not in great shape. Your tree may have been stressed by lack of water, edge trimmer or lawnmower injury, poor quality soil / poor drainage or sunscald.