Major Tree Diseases of the Century

Abstract

Tree diseases may be divided into three types: foliage diseases, canker diseases, and wilt dis- eases. Most foliage diseases are not fatal and can be controlled by fungicides. Many fungi that cause canker diseases attack mainly trees under stress. Maintaining trees in a vigorous growing condition will prevent these canker diseases such as Cytospora canker of spruce and Melan- conium canker of birch. However, some canker- producing fungi are highly virulent and will attack trees regardless of vigor, such as chestnut blight and white pine blister rust. Most wilt dis- eases are caused by organisms that are highly virulent and for which it is difficult to develop controls. The more destructive and widespread wilt diseases include elm phloem necrosis, Dutch elm disease, Verticillium wilt, and oak wilt. The six major diseases of the past century which I will briefly discuss are dwarf mistletoe, chestnut blight, white pine blister rust, elm phloem necrosis, Dutch elm disease, and oak wilt.