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Guide to Common Local Tree Diseases

How to Use This Guide

This guide is meant to help anyone trying to diagnose symptoms on trees in Humboldt and Del Norte counties. To begin, click on the tree species of interest. This will take you to three tables, where symptoms are listed by location on the host plant. Click on whichever symptom/s are most prominent to see the most likely cause/s of this symptom/s. This guide does not list every disease that occurs on tree species in this area, but rather covers the most commonly encountered forest pathogens along the North Coast. If your tree exhibits symptoms that do not match any of the listed pathogens, please use this guide as a starting point for further investigation and contact Wallis Robinson, Staff Research Associate II at wlrobinson@ucanr.edu or Yana Valachovic, Forest Advisor and County Director at yvala@ucanr.edu.

Common Tree Species

Douglas-fir (Pseudotsuga menziesii)

Sitka spruce (Picea sitchensis)

Madrone (Arbutus menziesii) - Coming Soon

Tanoak (Notholithocarpus densiflorus) - Coming Soon