Tree Diseases & Pests in Ontario

Worried about pests or diseases affecting your trees? This section features articles written by certified Ontario arborists to help you understand the most common threats to tree health in our region—from fungal infections to invasive insects.

Here you’ll find expert advice on identifying early symptoms, spotting harmful patterns, and knowing when to take action. Whether you’re dealing with dying leaves, strange bark damage, or unknown pests, our articles give you the practical knowledge to protect your trees and your property.

We cover topics like verticillium wilt, beech bark disease, white pine blister rust, Dutch elm disease, oak wilt, and more. You’ll also learn about invasive species like the Asian longhorned beetle and how they impact local tree populations.

Each article is backed by real experience from the Sarginson’s team—ISA-certified arborists who diagnose, treat, and remove diseased trees across Toronto, Durham Region, Peterborough, and beyond.

Not sure what’s affecting your tree? These guides are a great place to start. If you need a second opinion, just Ask the Arborist or book an inspection.