This is in continution to my previous post Diseases of Apple: Powdery Mildew Management. Here we are going to talk about the Collar Rot that is similar to Root Rot and Crown Rot. This disease is tedious to be managed but if understood throughly it can be managed.
The disease is caused by Phytophthora cactorum and infection starts from the collar region i.e. soil line and spread mostly to the underground parts and the above ground stem portion is also infected in highly susceptible scion cultivars. The fungus attacks the cambium thusrequires wounds to cause infection, once infected bark at the soil level becomes coffee brown in colour, slimy and rots resulting in cankered areas. The wounds are irregular in outline but usually roughly oval which extend rapidly, often resulting in girdling of the tree. The attacked trees are recognized by sparse foliage, purple colour of the leaf veins in attcked tree, more number of spurs than normal, fruit size remain small in such trees as nutrition uptake is reduced due to rot.
In coming post we shall be talking about the Collar Rot Management.