Figure : Phytopthora-induced root rot and decline of a Nagpur mandarin tree
Phytophthora root rot is a serious, widespread and difficult to control fungus disease affecting a wide range of plants. Root rot occurs when the cortex of fibrous roots is infected, turns soft and appears water-soaked. Fibrous roots slough their cortex leaving only white thread-like stele.
Symptoms
Early signs of infection are often difficult to observe but include darkening of young feeder roots and occasionally the larger roots, reduction in the glossiness of the leaves, leaf drop and dieback. The foliage may wilt, yellow and dry up. The base of the trunk may swell and splits may form and large cankers may develop. The damage caused by the disease most often occurs or is observed in summer when plants are drought stressed. The plant is unable to adequately absorb enough water from the soil because its roots are damaged and consequently often die.
