Top Of Willow Tree Dead . I bought a weeping willing two summers ago. The fungal disease cotton root rot (phymatotrichum omnivorum), usually associated with cotton plants, can cause willows in the southwestern u.s. Dead Tree On Mountain Top Free Stock Photo Public Domain Pictures from publicdomainpictures.net Why is my willow tree dying? Apply mulch made of wood chips or bark around the tree's base to help the soil retain moisture and prevent weeds from growing. I bought a weeping willing two summers ago.