Keeping plants growing vigorously by watering and fertilizing is extremely important. Also, with such diseases as Verticillium wilt and Dutch elm disease, pruning out affected branches usually is of vital importance. Verticillium Wilt Verticillium is a soil fungus that attacks many trees and shrubs. The most susceptible plants include ash, barberry, catalpa, linden, maple, Russian olive, smoketree and redbud. Beech, birch, hawthorn, hickory, honeylocust, mountain ash, white and bur oak and sycamore appear to be more resistant.
Evergreens are resistant to the disease.
The fungus attacks plants through roots and wounds, growing internally in the vascular system. This internal growth in the sapwood of plants causes nutrient and water deficiencies in the upper branches. A variety of symptoms may occur, but yellowing and wilting of leaves on one or two branches is most common. Sometimes green streaks can be found in the sapwood beneath the bark. Diseased limbs should be removed and destroyed.