A Study on the Control Index of Valsa Canker of Armandii Pine

The invertory of permanent sample plots and stem analysis were used to study in Arm and ii Pine stands which was seriously attacked by Valsa pini.The results showed that there were some relationships between the disease grades and loss ratio, mean annual increment of tree height, diameter class and tree volume.Thus, correlative coefficient of volume loss ratio (y)in every disease index (x), the loss ratio of Valsa canker on Arm and ii Pine, economic injury threshold and the estimated pattern of control index have been derived.