Abstract:

Xylotrechus namanganensis Heydel is a dangerous pest to broadleaved ornamental tree species in the northern plain area in Xinjiang.Adults of this pest eat little, they only take in honey in the flowers or juice of the trees and do not directly harm the trees.Whereas other forms of the pest cause damage to the trees, since all the eggs, larvae and pupae live within trunks of the trees, which delays sprouting, advances leaf shedding, and halters grow th of the infected trees.Both DBH and height of the infected plants were significantly smaller compared to those of the healthy ones.Consequently the timber volume of the former was remarkably less than that of the later.There was linear regression relationship between reduction of timber volume and the number of insect cavities, i.e.Y = 3.9008 +1.6874X, (r =0.9841 ^**).The infestation index might be indirectly determined in the light of the number of eclosion cavity of the adults, though larvae of the pest bore and take food inside the trunk.Most of eclosion cavities of the adults appeared within the height of 2.5m above the ground.According to the principle that the retrieved loss should be equal to or greater than the expense on pest cont rol, the economic injury level(EIL) of Xylotrechus namanganensis Heydel should be set as 2 eclosion cavities per plant.

Key words: Xylotrechus namanganensis Heydel, Injury loss, Ulmus pumila var.pyramidalis