Tree leaves in fall have disease spots

Q: My sugar maple and tulip poplar tree leaves have terrible brown spots and holes in them. What is causing this?

A: This is normal fall behavior for many deciduous trees and shrubs. The plant receives signals, like shorter day length and lower temperatures, and begins pulling anything useful out of the leaves and down to the stems and roots for storage in winter.

Some of the chemicals it pulls out are used to defend against disease. When defenses are gone, leaves get disease spots on them quickly.

The same thing is happening when the tree pulls green chlorophyll out of the leaves so the yellow carotenoids underneath can be seen before the leaf drops.

  • Advertisement