Scab Gardening Advice Scab is similar to a large leaf spot, but the affected area looks dull, is usually dark olive green and has indefinite margins. The fruit symptoms are usually sunken, corky, dark olive areas. The sunken appearance is due to the death of underlying tissue.
Cankers usually have distinct margins between dead and living tissues.
They may grow slowly, increasing in size year after year. Gardening Advice Oak wilt is caused by a fungus carried by sap- feeding beetles and certain other insects that visit wounds in bark. Dead woody twigs and branches, generally in the top of the canopy, are the symptom of dieback in trees and shrubs. Dieback may be the result of decline, canker fungi or winter injury. Root Rots Gardening Advice Thielaviopsis and other soil-inhabiting fungi frequently cause serious root rots, particularly on herbaceous ornamental plants.