Dutch Elm Disease: What an Arborist Should Know1

In order to control Dutch elm disease, one must be aware of a few essential facts concerning the anatomy and function of elm wood. It is amazing how ineffective the most strenuous efforts can be if these facts are ignored. First of all, elm is a ring-porous tree, like chestnut, oak, and ash (Fig. 1). This means that the bulk of the water is carried to the crown via the wide earlywood vessels of the xylem (wood) of the most recent growth ring (Huber, 1935). In other words, most of the water moves in a very thin layer of wood, immediately beneath the cambium. Wide and long vessels, like those of elm, are extremely efficient: those of a single growth