Canker diseases not only disfigure a tree, they also create entry points for:

Canker diseases cause damage to the bark of trees, leading to open wounds that can serve as entry points for other pathogens and pests. Among these, wood decay fungi are particularly relevant as they can enter through the wounds created by canker diseases. When the bark is compromised, it allows these decay organisms to colonize the woody tissues beneath, potentially leading to further deterioration of the tree’s structural integrity and overall health.

In contrast, lightning strikes and leaf-spotting organisms do not interact with the tree in the same way. Lightning strikes are a separate environmental factor that entails risk due to natural phenomena rather than biological entry points. Leaf-spotting organisms typically affect the foliage rather than the woody structure. While beneficial insects may interact with the tree ecosystem positively, they do not directly exploit the weakened structure caused by canker diseases for entry or feeding. Thus, the most logical and relevant answer in this context focuses on the wood decay fungi that take advantage of the damage caused by canker diseases.