Abstract: The densities of grasshoppers on rangeland treated with N. locustae baits were reduced, and there were two peaks of infection of the pathogen among grasshoppers during the treated season.The results of field experiments showed that the infections of N. locustae were influenced by the application rates of the N.locustae baits, the densities of the pests, and the time dynamics of the predominant species of grasshoppers.It was found that the pathogen had been existing in the grasshopper populations in the places where were treated with N.locustae baits only once several years ago when we surveyed in 1993.

Key words: Infection, Epizootic, Nosema locustae, Biocontrol, Rangeland

摘要： 在内蒙古乌盟达茂旗蝗害常发区,应用蝗虫微孢子虫(Nosema locustae Canning)后,主要优势种蝗虫,亚洲小车蝗(Oedaleus asiaticus)、宽须蚁蝗(Myrmeleotettix palpalis)、白边痂蝗(Bryodema luctuosum)和皱膝蝗(Angaracris spp.)等均可感染该病。应用后的当年,混合种群的感染率曲线是双峰型,后一峰值较高,表明该病原物可以自然流行于该地区内的蝗虫种群中。1993年分别对1988年、1989年、1991年和1992年应用蝗虫微孢子虫饵剂处理区进行定点取样调查结果表明:在应用蝗虫微抱子虫治蝗多年后的草场上,蝗虫种群中仍有蝗虫微孢子虫病存在,在有些年份可形成一定规模的流行。主要优势种蝗虫的平均感染率在应用后的不同年份中有差异。田间小区试验结果表明蝗虫微孢子虫的应用剂量也是影响蝗虫微孢子虫病流行曲线变动的重要因素。

关键词: 蝗虫微孢子虫, 生物防治, 疾病流行, 感染率, 虫口密度