Abstract: The damage caused by arthropod pest is a main factor restricting the production of alfalfa.Studying the population dynamics and interaction between main arthropods pest and their natural predators in alfalfa field is the foundation of IPM.The population dynamics of main arthropod groups in alfalfa field were investigated in DingXi,Gansu Province.The results show that the main insect pests were Therioaphis trifolii Monell,Acyrthosiphon pisum Harris,thrips,and plant bugs,etc.The major arthropod natural predators were coccinellids,green lacewings,syrphid flies,parasitic wasps,Orius minutus L.,and spiders etc.The population fluctuation pattern of T.trifolii, A.pisum,and thrips was of one peak in the last ten days in June,the first ten days in July,and the first ten days in July,respectively,and the fluctuation models were established.The interactions between aphid and coccinellids,green lacewings,syrphid flies,parasitic wasps,spiders,between thrips and O.minutu,and between plant bugs and spiders were analysed;significant interactions between the populations of main arthropod natural predators and insect pests were detected.The occurrence of natural predators manifested an obvious ‘time follow’ phenomena which was 10-20 days later than that of pest.

Key words: Alfalfa, Arthropod, Insect, Population dynamics

摘要： 对甘肃省定西市九华沟苜蓿(Medicago sativa)田节肢动物主要种类的数量动态进行系统研究,结果表明:苜蓿田主要害虫是苜蓿斑蚜(Therioaphis trifolii)、豌豆蚜(Acyrthosip hon pisum)、蓟马(Thripidae)和盲蝽(Miridae)等,主要天敌是瓢虫(Coccinellidae)、草蛉(Chrysopidae)、食蚜蝇(Syrphidae)、寄生蜂、小花蝽(Orius minutes)和蜘蛛等;苜蓿斑蚜、豌豆蚜和蓟马在苜蓿上的消长动态呈单峰型,高峰期分别出现在6月下旬、7月上旬和7月上旬;建立了苜蓿斑蚜、豌豆蚜、蓟马和盲蝽的时序动态模型;蚜虫与瓢虫、草蛉、食蚜蝇、寄生蜂、蜘蛛、蓟马与小花蝽,盲蝽与蜘蛛的相互作用表明主要天敌与害虫自然种群数量之间呈极显著的互作关系,天敌的发生出现明显的时间跟随现象,比害虫推迟10-20 d。

关键词: 苜蓿, 节肢动物, 昆虫, 种群数量动态