改制毛竹林害虫虫情变动的探讨

改制前的毛竹林，每两年有一年无笋或少有笋、有几个月林内立竹上无叶，竹子上的害虫种类简单，危害不重，有些害虫少发生或不能发生；能发生或危害重的竹子害虫，在生活过程中，习性多少都发生一些变化，如竹织叶野螟有迁飞习性，毛笋泉蝇、毛竹黑叶蜂部分蛹有滞育习性，赭翅双叉端环野螟有同时以小幼虫和老熟幼虫越冬习性，以适应无笋、少叶的营养环境。改制后的毛竹林地被物挖锄，天敌资源锐减，竹林中年年有笋，立竹上终年披叶，使竹子害虫食物条件改善，竹子害虫种类逐年增加，害虫迁飞、滞育习性的比例逐年减少，危害逐年加重。

A DISCUSSION ON INSECT PEST INCIDENCE IN RELATION TO SILVICULTURAL SYSTEMS IN PHYLLOSTACHYS PUBESCENS STANDS

Some phyllostachys pubescens stands have shown so-called "on year"and "offyear"characteristics in shooting when cultivated under traditional system. The "on year"and"off year" occur alternatively. In "on year", most bamboo plants produce new shoots, butleaves dry out in autumn and winter for sprouting new leaves next year. There are much lessor no shoots production and bamboo plants are well foliated with new leaves in "off year".These result in food pressure to insects feeding on shoots and leaves. Insect problems aregenerally not serious and some insects even can not survive in bamboo stands in the "on-off-year"cultivation system. Most of insects which can cause heavy damage have adaptive behav-iors, such as migration and diapause. However,new shoots are produced evenly between yearsin bamboo stands cultivated under new system. Provided with the improved food and nutri-tional condition,insect species,incidence and their damage are all in increasing and some mi-nor pests become important ones.