【目的】二化螟是危害水稻的重要害虫，其钻蛀为害，防治困难，严重威胁水稻生产。本研究对感染二化螟昆虫病原线虫的分离筛选和感染特性进行研究，期望为水稻钻蛀害虫危害的防治提供新的途径和方法。【方法】自越冬代二化螟幼虫体内通过组织分离筛选，获得野外感染二化螟的昆虫病原线虫，室内接种实验分析分离昆虫病原线虫对二化螟的感染活性和作用特性。【结果】自然罹死二化螟幼虫体内分离获得野外感染的昆虫病原线虫N-Yz1，接种4龄二化螟幼虫导致感染并死亡，后期虫体内产生大量形态一致的侵染期线虫(IJ)。形态学观察结合rDNA-ITS序列分析，鉴定分离昆虫病原线虫隶属于斯氏线虫属，与已鉴定种小卷蛾斯氏线虫同源性达99.87%。昆虫病原线虫N-Yz1对不同龄期二化螟幼虫都有较高感染致死作用，40头(IJ)的线虫接种剂量，对低龄(2~3龄)二化螟致死速度快、致死率高， 接种2 4 h 就出现感染致死个体，48 h后幼虫全部死亡。高龄幼虫(4~6龄)感染致死速度较慢，死亡高峰发生在接种线虫后的48 h。N-Yz1接种剂量与二化螟死亡率呈显著正相关，剂量超过30 IJs/头时，4龄二化螟感染死亡率达90%以上。N-Yz1对二化螟幼虫具有明显搜索能力，在距离寄主害虫0-30 cm的范围内，通过迁移扩散，感染二化螟并导致其死亡。【结论】分离昆虫病原线虫N-Yz1具有较强的感染致死能力，表现出防治水稻钻蛀害虫二化螟的潜在应用价值。

【Objective】 The rice stem borer [Chilo suppressalis (walker)] is an important pest to rice that threatens rice growth. The fact that it bores into rice stems adds to the difficulties of control. This study focuses on the isolation of the entomopathogenic nematodes of C. suppressalis and analysis of the infection of the pest to provide new strategies and methods for the control of boring pests on rice. 【Method】 We obtained and identified entomopathogenic nematodes from the overwintering generation C. suppressalis in the rice stubbles through tissue isolation. Then, the lethal effect and infecting characters of the isolated entomopathogenic nematodes against the C. suppressalis were analyzed by inoculation into the larvae of C. suppressalis. 【Result】 The wild-infected entomopathogenic nematode named N-Yz1 was isolated from dead larvae of C. suppressalis, then the isolated nematodes were inoculated into the 4th instar larvae of C. suppressalis, leading to their infection and death, with mass nematodes emerged in the dead larvae. Based on the morphological features and analysis of the sequences of rDNA ITS, the strain of N-Yz1 was identified in the genus of Steinernema, which shared the homology of 99.89% with that of the species of Steinernema carpocapsae. The nematode N-Yz1 had highly infectious and lethal effects on different instar larvae of C. suppressalis. Inoculation with a nematode dose of 40 IJs per larva resulted in rapid lethality and high mortality of the juvenile larvae (the second and third instar), with infected lethal individuals appearing within 24 h after inoculation and the death of all larvae 48 h later. For the elder larvae (the fourth to sixth instar), the killing speed was relatively slow, with peak mortality occurring 48 h after nematode inoculation. We also found that positive correlation between inoculum dosage of N-Yz1 and the mortality rate of C. suppressalis. The mortality rates of the 4th instar C. suppresalis were more than 90% when the inoculation dose exceeded 30 IJs per larva. The results also showed that N-Yz1 could forage C. suppressalis larvae within the distance of 30 cm, and kill the larvae through immigrating and diffusion. 【Conclusion】 The isolated entomopathogenic nematode N-Yz1, a strain of Steinernema, has strong infective and lethal effect, and potential applications for the control of the rice stem borer, C. suppressalis.