Sick trees

For the past three years, maples in the Charlottetown area have been getting sick. By mid-August, the leaves are curled and brown and starting to fall. Looking closer, the leaves are dotted with black raised dots called Tar Spot fungus.

Tar spot won't kill the tree, but it sure makes them ugly. And there won't be the traditional amazing display of colour that only a maple can show off in the fall. This fungus thrives in warm damp conditions, and it is less likely to be killed off in cold conditions because our winters have been mild. Experts advise raking up and disposing of fallen leaves, but that is difficult because they take their time, and don't drop off all at once. They are also blown around by the wind and disappear. It also means I can't use leaves as mulch or compost them, because that fungus will still be present.
Most of the maples in the area are affected - and they all happen to be non-native Norway maples. But not 20 feet from this ugly specimen on my lawn are two maples that show no sign of the disease. These are sugar maples, a native variety, and it's great to see that some maples are resistant. And the fall colour show will happen in a smaller way this year.
Norway maples were planted everywhere because they were cheap, grew well, and were resistant to cold. But now they are all looking terrible. This is a good example of why we should be careful not to plant a monoculture. Too much of the same thing is definitely not a good thing. When we have more variety and one species is attacked by disease, it doesn't make such a big impact.