The humid and wet weather of the past few years has favored the development of a fungus that causes tar spots on several varieties of maple trees located in an urban setting.
The tar spot is easily noticeable. If you see one or several black spots, shiny and raised and measuring up to 1 cm in diameter of the top of leaves towards the end of summer, it means your tree is infected.
A severe infection can interfere with photosynthesis and cause the infected leaves to fall prematurely. The problem is rarely serious, the dark spots on the leaves merely reduce the esthetic appearance of the tree.
A good way to fight against this fungus is to remove and destroy the leaves in autumn. Putting the infected leaves in your residential compost will not destroy the fungus because le mix doesn't reach a high enough temperature. However, putting the leaves in the municipal compost heap, where the composting process reaches a temperature hot enough to neutralize the fungus, is recommended.