柳蛎蚧防治阈值的研究

根据目前杨树人工林经营的一般水平．对柳蛎蚧防治阈值进行了研究。当材积损失率为16％时．作为受害允许阈值的第一水平．相应的受害允许密度为14.70头／cm2，当低于此虫口密度时，保护，利用天敌进行控制：当达到此虫口密度时．结合人工防治方法进行控制．材积捐失率达30％作为受害阈值的第二水平．相应的受害允许密度是21．93头／cm2．达到此虫口密度时．应采取人工助迁天敌的方法．并结合人工防治进行控制。材积损失率达60％作为受害允许阈值的第三水平．相应的受害允许密度为37.39头／cm2、此时应采取人工防治与化学防治相结台的措施．并结合抚育伐伐掉受害严重木．清除虫源，同时应注意保护天敌．化防时把天敌助迁到其它林分。

Control Threshold of Willow Oyster Scale

The control threshold of willow oyster scale( Lepidosaphes salicina Borchs) was studied based on the current management level of poplar plantation. 16% loss of timber volume was considered to be the first allowable level of control threshold and the relevant insect density is 14.7 heads/cm 2. Protection and use of natural enemies are first consideration to control the pest when the insect density is under the first level. Artificial control methods should be adopted while the insect density reached this level. 30% loss of timber volume was defined as the second level of control threshold, with an insect density of 21.93 heads/cm 2. For this insect population density, artificial migration of natural enemies should be used, with combination of artificial control methods. 60% loss of timber volume with an insect density of 37.39 heads-cm 2, was defined as the third level of control threshold. For this damaged level, the control measures in combination of artificial control and chemical control should be used. The serious infected trees must be cut in order to eliminate the pest source. Much attention should be paid to natural enemies when chemical control is adopted.