昆虫病原线虫N-Yz1对水稻二化螟的控制作用

Control Effect of Entomopathogenic Nematode N-Yz1 to Rice Stem Borer,Chilo suppressalis

昆虫病原线虫N-Yz1是自二化螟罹死虫体分离的小卷蛾斯氏线虫,作为防治二化螟的生物因子具有广泛应用潜力。本文通过小卷蛾斯氏线虫N-Yz1对二化螟幼虫的侵染过程、不同龄期二化螟的感染和田间二化螟的控制作用分析,研究N-Yz1对水稻二化螟的控制作用及防治技术。结果表明,N-Yz1对二化螟具有较强的侵染活性,可以直接穿透昆虫表皮入侵虫体组织。病原线虫的迁移依赖接触表面游离水的存在,线虫个体侵染能力也表现出显著差异性,直接影响到N-Yz1的感染速度和感染效率。N-Yz1对不同龄期的二化螟都具有较高的致死活性,低龄幼虫(1~2龄)敏感性高于高龄幼虫(3~5龄)。室内模拟试验表明,水稻拔节期使用N-Yz1对二化螟防效不高,2.4×10^(5) IJs/m^(2)剂量仅为37.3%,而防治稻茬越冬代二化螟防效明显提高,N-Yz1相同剂量防效达85.2%。田间试验进一步证明,夏季稻田2.4×10^(5) IJs/m^(2)剂量N-Yz1防治二代二化螟防效21.23%,增加使用剂量可以提高控制效果;而春季稻茬田应用N-Yz1,1.2×10^(5) IJs/m^(2)剂量药后15 d防效达53.7%,45 d后高达79.1%。因此,可以针对稻茬二化螟主要繁殖虫源,采用N-Yz1防治稻桩中越冬代二化螟幼虫,显著降低害虫发生基数,控制水稻钻蛀害虫二化螟的发生和危害。

The rice stem borer,Chilo suppressalis(walker)is an important pest to rice that threatens the rice growth by boring into stems.Steinernema carpocapsae N-Yz1,the natural enemies isolated from dead larvae of rice stem borer,are considered a potential biological control agent for C.suppressalis.Based on the invasion process,the infection to different instar larvae,and field effect,the control effect and using method of N-Yz1 to C.suppressalis was explored.The analysis of invasion process revealed that N-Yz1 possessed great infective action and could enter the body of larva by penetrating from the skin.Free water was essential for the movement of N-Yz1 on the surface it contacted.Infection ability was significantly different among different individuals of N-Yz1,which caused a different rate and ratio of invasion to the larvae of pest.The nematode N-Yz1 had a highly lethal effect on all the instar larvae,while juvenile larvae(1―2 instar)were sensitive to elder larvae(3―5 instar).Lab tests indicated that the control effect of N-Yz1 on field larvae of C.suppressalis was not high at the stage of rice elongation,the mortality of the larvae was 37.3%at a N-Yz1 dose of 2.4×10^(5) IJs/m^(2).In contrast,simulation of control wintering larvae by N-Yz1 was much higher,with larval mortality of 85.2%at the same dosage.Field tests further demonstrated that the effect of N-Yz1 on C.suppressalis was just 21.23%at the stage of second generation of pest in summer,although higher mortality might be caused by an increasing dose of N-Yz1.It was also confirmed that,using N-Yz1 against wintering larvae in rice stems at spring,the mortality was 53.7%at 15 d at a dose of 1.2×10^(5) IJs/m^(2),and increased to 79.1%at 45 d.It was indicated that N-Yz1 can be used to control the wintering larvae in rice stems which is main multiply source of the pest,reduce the base quality and effectively control the damage caused by the borer pest.