Book excerpt: A large number of diseases and disorders can affect forest trees in Britain. Confidence in identifying particular causes from this range of potential problems requires a combination of knowledge and experience that is not easily acquired without becoming a specialist in the field. Part 1 of this book offers guidelines by which managers and owners can investigate health problems in their trees. Part 2 offers a key to the most common problems of plantation trees, and in Part 3 important features of some of the diseases and disorders covered in Part 2 are summarized.