Vertlicillium wilt causes the leaves of weeping cherry trees to turn brown and wilt, according to Garden Guides. The disease is caused by a fungal infection. The leaves of an afflicted tree will have veins that turn red from vascular damage, curl, droop or wilt, turn yellow and then brown before dropping from the tree. Verticillium wilt first attacks the roots and then the wood of the tree.
Garden Guides also notes that Verticillium wilt often turns the tree's wood to a yellowish brown color. Verticillium wilt can be fatal to the tree within two years, though some trees do survive. Garden Guides lists additional diseases that affect weeping cherry trees as gray mold, wood rot, and decay. Gray mold attacks the tree's branches, stems, leaves and flowers. It originates from mold spores that live in the leaf litter that surrounds the tree. The spores transfer from the litter to the trunk and infect vulnerable tissue. The mold leaves a gray fur on the infected parts of the tree. Wood rot is caused by fungi that invade the interior wood or roots of the tree. The fungi attack only decaying wood. Symptoms include crusts, shelf-like bodies attached to the trunk or wood rot that creates holes in the tree.