苹果园植被多样化在果树害虫持续治理中的作用

笔者于1997年至1999年对4个不同类型苹果园进行了系统调查研究，结果表明，在植被多样化的生草园，主要捕食性天敌的平均虫口密度为0．38头／枝，分别是免耕园、清耕稀植园和清耕密植园的3．4倍、2．7倍和1．8倍；寄生性天敌的寄生率达63．5％，分别是免耕园、清耕稀植园和清耕密植园的1．4倍、16．7倍和18．1倍；生草园在未施用任何杀虫、杀螨剂的情况下，树冠上害虫的平均虫口密度均低于免耕园、清耕稀植园和清耕密植园，其比值，蚜虫为1：1．1：18：1．62：1．99，叶螨为1：4．27：2．78：7．22，金纹细蛾为1：1．70：50：4．10。同时，果园植被多样化后地面植被上和树冠上天敌逐年增加，益害比大大提高，从而，天敌的自然控制作用可有效地控制果树次生害虫的危害。

The Plant Diversity in Apple Ecosystems Toward Sustainable Pest Management

From 1997 to 1999, the investigation on apple insect pests and their natural enemies in four different apple orchard ecosystems was systematically carried out in Beijing. The results showed that the average population density of the dominant specise of predators on the apple trees in cover cropping system was 0.38 individuals per branch , which was 3.4 times as large as that in non-tillaged system and 2.7 times as large as that in the light planting clean cultivated system and 1.8 times as large as that in the combine planting clean cultivated system .The ratio parasitized of parasitors on apple trees in cover cropping system was 63.5%, which was 1.4 times as large as that in non-tillaged system and 16.7 times as large as that in the light planting clean cultivated system and 18.1 times as large as that in the combine planting clean cultivated system .The average population density of pest was lower than the non-tillage system and clean cultivated system without pesticide applications in cover cropping system. The ratio of aphids was 1∶1.18∶1.62∶1.99, the ratio of pest-mites was 1∶4.27∶2.78∶7.22, and the ratio of lithocolletis rignoniella Mats was 1∶1.70∶4.50∶4.10 .The natural enemies on cover crops and on the apple trees in cover cropping system were annually increased . The predator/prey ratio was evidently increased . Thus the natural enemy had controlling the secondary induced pest.