The 6-class dwarf mistletoe rating system.
[See FA 23, 2224]. In the 6-class rating system applied to Arceuthobium spp., each third of the live crown is rated as 0 (no mistletoe), 1 (light mistletoe, less than half the branches infected) or 2 (heavy mistletoe). The ratings for each third are summed to obtain the total for the tree. The uses and limitations of the system are described, and 5 examples of its application are given.