梨园使用的杀虫剂大多数属于广谱性的 ,它们对靶标害虫、非靶标害虫和益虫不同程度地具有杀伤作用 ,而对害虫的天敌而言由于农药的直接杀伤和食物的缺乏损失更为严重。化学防治的历史证明 ,一种药剂使用一段时间后 ,能使原先不需要防治的次要害虫上升为主要害虫。近几年在梨园 Most pesticides used in pear orchards belong to a broad spectrum. They have various degrees of killing effects on target pests, non-target pests and beneficial insects, but are even more peculiar to natural enemies of pests due to direct killing of pesticides and lack of food serious. The history of chemical control proves that after a period of use of a medicament, the secondary pest that did not need to be controlled can be increased to a major pest. In recent years in Liyuan