近几年来,在丘陵低山地区,马尾松毛虫为害频繁发生,危害猖獗,虽努力扑救,森林仍遭受重大损失;在平原湖区,蛀干害虫天牛危害杨树也呈泛滥之势。其中主要原因之一,是多年来选用同一树种大面积营造纯林之故。纯林为病虫害的发生繁衍、蔓延提供了十分有利的条件,以致虫害一旦发生, In recent years, in the hilly and low mountain areas, the masson pine caterpillar damage frequently occurs, the harm is rampant. Despite efforts to save the forest, the forest still suffered heavy losses. In the plains lake area, the borer pests also damage the poplar trees. One of the main reasons is that the selection of the same tree for many years has created a pure forest on a large area. Pure forest for the occurrence of pests and diseases multiply, spread provides a very favorable conditions, so that once the pest occurs,