菜青虫是菜粉蝶又名菜白蝶的幼虫，主要为害油菜、白菜、花菜、莲花白、萝卜、甘蓝等十字花科蔬菜。初龄幼虫多在叶背取食，主要咬食叶肉，留下一层半透明表皮；较大的幼稚虫多在叶面取食将叶片食成孔洞，仅剩下叶脉和叶柄，使幼苗早死，或不能正常包心。包心期受害的菜株，幼 Pieris rapae is a butterfly larvae of cabbage butterflies, the main damage rape, cabbage, cauliflower, lotus white, radish, cabbage and other cruciferous vegetables. The first instar larvae feed on the leaf back, the main bite the leaves, leaving a layer of translucent epidermis; Larger juvenile insects and more in the leaf feeding into the hole into the leaves, leaving only veins and petiole, seedlings premature death , Or can not be normal heart. Caused by the heart of the cabbage strain, young