在我国“三北”防护林体系中，杨树天牛问题越来越突出，其中以陕、甘、宁、晋、蒙为甚。１９９４年发生面积达３３．３万公顷，是８０年代初期的７倍；此后几年的发生面积虽未大幅度增加，但一些省区第一期工程营造的以杨柳为主的防护林，已大多毁于杨树天牛。杨树天牛灾... In our country’s “Three Norths” shelterbelt system, the problem of the poplar is more and more prominent, among which, Shaanxi, Gansu, Ningxia, Shanxi and Mongolia are even more prominent. In 1993, an area of ​​333,000 hectares occurred, which was seven times that of the early 1980s. Although the area of ​​occurrence in the next few years did not increase substantially, most of the willow-dominated shelter belts created by the first phase of some provinces and autonomous regions have mostly Destroyed in poplar days. Poplar days cattle disaster ...