Abstract:

Symbiotic fungi of Dendroctonus armandi such as Ophiostoma sp.and Leptographium sp.were the precursors to overcome the resistance system of host trees and the main factors to cause the host t rees to die.Symbiotic fungi destroyed the bleeding cells and developed in resin ducts, blocking up resin ducts of host trees.At the same time, following the development of symbiotic fungi in inner xylem of host trees, fungi hyphae solved epithelial cells of host trees, which resulted in the disorder of the nutrient and water metabolic of the host and the quick death of host trees.

Key words: Dendroctonusarmandi, Pinusarmandi, Symbiotic fungus, Resistance system, Lethal role