Spodoptera litura Fabricius is the serious, polyphagous pest of various crops. Due to the high resistant to most of chemical pesticides, it is hard to control S. litura in the fields. We investigated the virulence of four entomopathogenic nematodes (EPNs) in each larval stage. All EPNs were more effective to younger larvae than older larvae. Mortality, larval penetration rate and reproduction rate were significantly higher in H. indica, S. carpocapsae and S. longicaudum than the H. bacteriophora. Three high effective EPNs induced complete mortality of first instar larvae within 48 h, but of fifth instar larvae within 72 h. These EPNs also highly effective to control S. litura in pot assay. Thus, H. indica, S. carpocapsae and S. longicaudum, can be used as efficient biological control agents of S. litura.

현재 국내에 서식하는 곤충병원선충에 대한 라이브러리 사업이 계획되고 있다. 이 과정 중에 현재까지 Steinernema와 Heterorhabditis 속에 속한 12 분류군을 정리하고 있다. 이 가운데 7 분류군이 증식되었고 4 분류군이 선충과 공생세균의 동정이 실시되고 있다. 이들 4 분류군은 모두 Steinernema 속한 종으로 판단된다. 이들 Steinernema 선충의 감염태는 파밤나방(Spodoptera exigua) 5 령 유충에 대해서 차등성있는 살충력을 나타내어 유전적 차이를 암시하였다.

국내에 서식하는 곤충병원선충 유래 공생세균에 대한 라이브러리 사업이 진행되고 있다. 이 과정 중에 현재까지 4 분류군의 공생세균이 감염된 곤충의 혈림프로 부터 분리되었다. 생화학 특성 분석 결과 이들 세균은 모두 장내세균의 특징을 지니고 있었다. 이들 모두는 파밤나방에 대한 높은 살충력을 지녔으며 Xenorhabdus 속의 균주 특성을 지니고 있었다. 이들의 종 동정은 16S rDNA 서열을 바탕으로 확인하였고, 이러한 동정 결과는 이들 세균의 성장에 이용되는 탄소원 특성으로 뒷받침하였다. 현재까지 동정 결과는 X. bovienii 한 종이 이들 공생세균에 포함되어 있다.

Fungus gnat, Bradysia impatiens is the most serious pest of different vegetable crops, mushroom and ornamental crops. In this study, we compared the control efficacy of two entomopathogenic nematode; Steinernema carpocapsae and Heterorhabdistis indica in Bradysia impatiens last instar maggots at 25℃ in laboratory. Our present study shows that, nematode infection and reproduction both were higher in the warm adapted nematode H. indica than the cold adapted S. carpocapsae. Therefore, entomopathogenic nematode H. indica can be use for control the Badysia impatiens as the efficient biological control agent.

Diversity and distribution of entomopathogenic nematodes were surveyed in Korea from 2010 to 2014. Soil samples were examined for the presence of steinernematid and heterorhabditid nematodes by baiting method with Galleria mellonella larvae. Out of the 189 soil samples, 47(24.9%) were positive for entomopathogenic nematodes, with the share of 7(3.7%) for Heterorhabditis and 40(21.2%) for Steinernema isolates. Morphological and molecular studies were also utilized to characterize isolates. The Heterorhabditis isolates were identified as H. megidis and Steinernema isolates as S. carpocapsae, S. monticolum and S. kraussei, respectively. H. megidis was the most common species of Heterorhabditis, which was isolated from 7 sites across the five different provinces and Steinernema monticolum was the most common species of Steinernema, which was isolated from 34 sites, respectively. S. carpocapsae was isolated from only two sites, Namwon, Jeongnam province and Iksan, Jeonbuk province, respectively. S. kraussei was the first recorded entomopathogenic nematode in Korea. Those entomopathogenic nematodes were recorded from coniferous and deciduous forests.

Spatial association of entomopathogenic and free-living nematode populations were analyzed at the landscape scale. Free-living nematodes were classified into functional guilds based on their trophic level (i.e. bacterivores, carnivores, fungivores, and omnivores) and life history characteristics (i.e. r-selected colonizing versus K-selected persisting species) in the soil ecosystem. Differences in life history traits were hypothesized to result in different spatial associations of populations. Spatial aggregation indices were calculated for each nematode group. Spatial associations were analyzed and compared for entomopathogenic nematodes (EPN) and each trophic/life history group of free-living nematodes based on spatial analysis of distance indices (SADIE). Spatial aggregation indices (Ia) revealed that taxa with more K-selected persisting life history were less aggregated in their habitat, whereas more r-selected colonizer life history types showed more aggregation. Spatial aggregation index of EPN populations was similar to that of relatively r-selected colonizer type free-living nematodes, which share several life history traits including high reproductive rates and insect phoresy. There were substantial spatial associations between EPN and r-selected colonizer life history free-living nematode taxa.

본 연구는 누에의 식엽성 곤충을 대체할 실험곤충으로서의 유용성과 자외선이 한국산 곤충병원성선충 (Heterorhabditis sp. 202 strain, Heterorhabditis sp. Gyeongsan strain, Steinernema sp. 223 strain, S. carpocapsae Pocheon strain, S. glaseri Dongrae strain, S. longicaudum Nonsan strain) 의 병원성과 생존에 미치는 영향을 알아보기 위하여 수행하였다. 누에에 대한 곤충병원성선충의 병원성을 조사한 결과 누에의 령기나 곤충병원성선충의 계통이나 종에 따라 상이한 병원성을 나타내었는데 5령충에 대해서는 Steinernematidae선충의 병원성이 높았고, 1령충에 대해서는 Heterorhabditidae선충의 병원성이 높았다. UV-C는 곤충병원성선충에 유해하여 노출 60분후에는 모든 선충이 치사되었다. UV-C 조사는 곤충병원성선충의 병원성에도 영향을 미쳐 노출 10분 후에도 누에나방 3령충에 대하여 6.7% 이하의 보정사충율을 나타내었다. 야외 뽕나무밭(UV량: 2.3mW/㎠)에서 곤충병원성선충, S. carpocapsae Pocheon strain을 엽면 살포 4시간 후 채취한 뽕나무 잎을 급상한 누에는 치사되지 않았다. 뽕잎에서 4.0mW/㎠의 UV 1시간 노출은 곤충병원성선충, S. carpocapsae Pocheon strain의 누에에 대한 병원성에 차이를 보이지 않았다.

Effect of four nematicidal herbal extracts (Daphne genkwa, Eugenia caryophyllata, Quisqualis indica and Zingiber officinale) and 3 acricidal herbal extracts (Pharbitis nil, Xanthium strumarium, and Desmodium caudatum) on entomopathobenic nematodes [Steinernema carpocapsae Pocheon strain (ScP) and Heterorhabditis sp. Gyeongsan strain (HG)], silkworm (Bombyx mori), and ground beetles (Synuchus sp.) were investigated in the laboratory and field. D. genkwa was highly toxic to ScP and HG (100% mortality) at the concentration of 5,000 ppm in X-plate. All the infective juveniles of HG were dead after 3 days by E. caryophyllata and Q. indica. The mortality of ScP and HG was below 10% by D. genkwa, D. caudatum, E. caryophyllata, Q. indica and Z. officinale at the concentration of 1,000 ppm two days after treatment while mortality of HG was 62.8% by D. genkwa at the concentration of 1,000 ppm in X-plate. However, 1,000 ppm had not effect on nematode survival and pathogenicity of ScP in sand column. On the contrary, E. caryophyllata had effect on pathogenicity of HG. Mean number of dead Galleria mellonella larva of HG was 0.5 in E. caryophyllata treatment. Q. indica did not effect silkworm reared on mulberry leaves at the treatment of 1,000 ppm in 10 days after treatment. However, there were 20.0 and 100% mortalities in the treatment of D. genkwa 3 and 10 days after treatment, respectively. The weight of silkworm was low in D. genkwa and did not pupate. The weight of pupa and cocoon were not different in E. caryophyllata, P. nil, Q. indica, X. strumarium and Z. officinale. D. genkwa, E. caryophyllata, P. nil, Q. indica and Z. officinale had no effect on ground beetles, Synuchus sp. in forest soil.

Five effective strains against tobacco cutworm, Spodoptera litura (Lepidoptera: Noctuidae), Steinernema carpocapsae (GSN1), Steinernema sp. (GSNUS-10), Steinernema sp. (GSNUS-14), Heterorhabditis bacteriophora Hamyang (HbH), and Heterorhabditis sp. (GSNUH-1) were selected among 14 isolates of Korean entomopathogenic nematode in laboratory tests. LC₅₀ values of above five strains against tobacco cutworm were various by different nematode strains and developmental stages of tobacco cutworm. LC₅₀ value of S. carpocapsae (GSN1) was the lowest by 4.0~8.3 infective juveniles (Ijs) and 2nd instars of tobacco cutworm was most susceptible. Pathogenicity of five effective strains against tobacco cutworm depends on nematode strain, concentration, and application times. The most effective strain was determined as S. carpocapsae (GSN1). Two or three times of applications were effective regardless of nematode strain, or concentration. Efficacy of S. carpocapsae (GSN1), Steinernema (GSNUS-10), Steinernema (GSNUS-14), and Heterorhabditis (GSNUH-1) was variable depending on nematode strain, concentration, application times, and host variety. S. carpocapsae (GSN1) was the most effective and inoculation of 100,000 infective juveniles per ㎡ (720,000 Ijs/7.2 ㎡=1×10⁹ Ijs/㏊) resulted in higher efficacy. Three times of application of nematodes led to higher control efficacy than one or two applications. Efficacy of nematodes was higher on Chinese cabbage than cabbage or kale.

Laboratory tests were conducted to determine the susceptibility of the alfalfa weevil, Hypera postica to Korean entomopathogenic nematodes, Steinernema carpocapsae GSN1 strain (ScG), S. glaseri Dongrae strain (SgD), Heterorhabditis bacteriophora Hamyang strain (HbH), and Heterorhabditis sp. Gyeongsan strain (HeG) at the petri dish assay. The larval mortality of H. postica was significantly different depending on nematode species and treatment concentration. SgD and HeG strain were more effective against H. postica larva than ScG and HbH strain. When SgD and HeG strain were treated with the rate of ＞20 infective juveniles (ijs) per alfalfa weevil larva, mortality was ca. 77.5-100% at the late instars of H. postica in 3 days. The number of established nematode was significantly different depending on nematode species, whereas number of progeny was not significantly different. The mean number of established ijs of SgD strain in a host was the highest at 80 ijs by 30.2. The highest progeny number of HeG strain was 2,671.5 with 80 ijs. All nematode strains were not parasitic entirely to H. postica adults. These results show that alfalfa weevil late larva is highly susceptible to Korean entomopathogenic nematodes in the laboratory.

Five strains of Korean entomopathogenic nematodes (EPN), steinernematids and heter-orhabditids were evaluated and tried in laboratory, pot, and vegetable greenhouses for environmentally friendly control of diamondback moth (DBM), Plutella xylostella, from 2002 to 2005. LC₅₀ values of five EPN strains against DBM were different depending on nematode strain and DBM instar. LC₅₀ value of Steinernema carpocapsae GSN1 (GSN1) was the lowest representing 2.6~3.9 infective juveniles (Ijs, 3rd stage) to 2nd to 4th instars of DBM. Pathogenicity of five effective strains against DBM was different depending on nematode strain, concentration, application times, and vegetable in pot. The most effective nematode was GSN1. Steinernema spp. was more effective than Heterorhabditis spp. against DBM. Two or three times of applications of EPN were effective regardless of nematode strain and concentration in pot. Efficacy of EPN was different depending on vegetable species. Efficacy was higher on Chinese cabbage, red mustard, and Ssamchoo than that on cabbage, kale, and leaf broccoli. Efficacy of GSN1, Steinernema GSNUS-10, Steinernema GSNUS-14, and Heterorhabditis GSNUH-l was variable depending on nematode strain, concentration, application times, and vegetable in greenhouse experiments. GSN1 was the most effective and 100,000 infective juveniles per ㎡ (=1 × 10⁹ Ijs/ha) resulted in higher efficacy. Three times of application of nematodes led to higher control efficacy than one or two applications. Efficacy of nematodes was higher on Chinese cabbage than cabbage or kale in greenhouse.

Korean entomopathogenic nematodes were introduced into cultural management of turfgrasses to enhance white grub control in golf courses for saving labour and expenses and contribution to giving safe playing and working places for golfers and superintendents by environmentally friendly control strategy. The turfgrass height influenced efficacy of entomopathogenic nematodes. Efficacy was higher at short turfgrass both in pot using Galleria mellonella larvae and in golf courses using 2nd instar of Exomala orientalis and Ectinohoplia rufipes as baits. Aeration increased the efficacy of entomopathogenic nematodes which were lower virulent. Pre-aeration was more effective than post-aeration. Exomala orientalis larval population was reduced 80.4 and 66.0% in the pre-aeration and post-aeration with entomopathogenic nematode, Steinernema carpocapsae Pocheon strain compared to 35.4% in the no aeration treatment.

골프장의 문제해충들 중 녹색콩풍뎅이(Popillia quadriguttata) 성충의 방제를 위하여 세 종의 한국산 곤충병원성선충 Steinernema carpocapsae KCTC 0981BP 계통 (ScK), S. glaseri Dongrae 계통(SgD), Heterorhabditis sp. KCTC 0991BP 계통 (HsK)을 이용하여 실험을 수행하였다. 3일 후, 녹색콩풍뎅이 성충 한 마리당 900마리의 선충을 처리하였을 때, 치사율은 ScK가 , HsK가 , SgD가 를 각각 나타냄으로써 이용한 선충 모두가 높은 병원력을 나타내었다. 성충 한 마리 당 900마리의 선충을 처리한 3일 후의 치사율은 ScK는 , HsK는 , SgD는 였다. 선충의 녹색콩풍뎅이 성충 표면부착율과 침입율은 접종 선충의 종과 밀도에 따라 차이가 있었다. 즉, 성충한 마리당 900마리의 선충을 처리하였을 때 녹색콩풍뎅이 성충의 표면에서 검출된 HsK의 비율은 였으며, SgD는 , ScK는 였다. 녹색콩풍뎅이 성충 내에 침입한 선충의 검출여부에 따른 선충의 침입율은 성충 한 마리 당 900마리의 선충을 처리한 3일 후 ScK는 , HsK와 SgD는 각각 를 보였다. 반면, 성충 한 마리 당 90마리의 선충을 처리한 3일 후의 ScK 검출율은 , SgD는 였으나 HsK는 발견되지 않았다.