OPAL’s seventh survey focuses on the health of our trees. In recent years the number of pests and diseases attacking trees has increased leading to a decline in tree health and in some cases tree loss. In order to manage these problems most effectively we need to study our trees and record information about their condition and any pests and diseases that are found.

The information and photographs in this guide will help you identify pests and diseases on Oak, Ash and Horse Chestnut trees and six of the Most Unwanted, helping you take part in our Tree Health Survey.