Field diagnosis through visual tree assessment is based on observable symptoms and signs of BRR. There are two steps. Step 1: Identify abnormal crown symptoms (e.g. sparse foliage density, abnormal foliage colour (chlorosis), abnormal leaf size, dieback twigs) as these are exhibited in infected trees. Step 2: examine the entire lower trunk, root collar and individual roots of the trees to look for typical signs of BRR disease, i.e. a) fruiting bodies of Phellinus noxius, b) mycelial encrustation, c) soil aggregates and d) mycelial nets. If a tree with a crown abnormality contains one or more of the typical signs of BRR disease under step 2 examination, the tree is considered infected with BRR disease.