An illustrated guide to the state of health of trees
Recognition and interpretation of symptoms and damage

Eric Boa

Diagnostic and Advisory Service
CABI Bioscience
Egham, Surrey, United Kingdom

Food and Agriculture Organization of the United Nations
Rome, 2003

The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

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FAO 2003



1 Introduction

Understanding tree health

2 Using the guide

Investigating problems

3 What is tree health?

Definitions and descriptions of key terms

Diseases, damage and disorders

4 Why trees become unhealthy

Causes of ill health in trees

Pest (biotic) influences

Non-living (abiotic) influences

5 Describing features of unhealthy trees

Recognizing features of ill health

Symptoms and their classification

6 Analysing the cause of symptoms

Interpretation of symptoms

Making a diagnosis

Problems in linking symptoms to causes

7 Colour plates: examples of ill-health in trees

Colour plates

8 Integrating different sources of knowledge

9 Technical support and advice

Diagnostic and advisory services

Collecting and sending samples

Annex 1
Definitions and explanations related to tree health

Annex 2
Guide to useful books and sources of information on tree health, insect pests and diseases

Annex 3
Tree hosts and health problems illustrated in the colour plates