Study on the Control Index of Dothiorella gregaria Canker of Poplar

Through experiment and Long term observation under natural condition on the pathogen′s numbers,loss of volume and disease index,the control index of Dothiorella gregaria canker of poplar was determined.The artificial inoculation and reinoculation results showed that the number of disease spots on stem,disease index and loss of volume were positively related to each other.For the 3～4 years old poplar when its DBH is over 3～4cm,the spots of disease is under 25 on stem,the disease index is 10,loss of volume is under 10%,which is the economic threshold for the saplings.When the spots on stem reach 50～75,the disease index is 20～30,loss of volume is 30%,managerial measures have to be adopted in some serious area.The spots on stem reach over 76～100,the disease index is 40～50,loss of volume is over 50%,large scale control must be carried out.