Witch's broom disease will strike when the cherry tree is infected by Taphrina wiesneri, an ascomycete with a form of saccharomycete, and at the top part of the tree twigs gather up and make what is called a 'nest of tengu' (nest of long-nosed goblin, or a witch's broom).
サクラてんぐ巣病はTaphrinawiesneriという酵母菌状の子嚢菌の感染により起こる病気で、その上部では小枝が密生して、いわゆる「天狗の巣」を作る。