Spelaeochthonius Morikawa, 1954, which comprises 11 species, is a genus in the family Pseudotyrannochthoniidae Beier, 1932. Members of this group can be represented by troglobitic characterisitics and narrow-range endemism. Three species are documented on the Korean Peninsula: Spelaeochthonius cheonsooi You, Yoo, Harms and Harvey, 2022; S. dentifer Morikawa, 1970; S. seungsookae You, Yoo, Harms & Harvey, 2022. In this study we utilize ten species, including three recorded Korean species, two Japanese species, and five new species, for molecular analysis. We employ four genes (COI, H3, 18S, 28S) commonly used in pseudoscorpions studies. This study aims to (i) identify the most specific gene for species identification in pseudoscorpions, (ii) demonstarate the narrow-range endemism of Spelaeochthonius, and (iii) explore the speciation pathway of this genus. Consequently, our understanding of biodiversity and necessity of species conservation.

The oriental fruit fly, Bactrocera dorsalis, is highly polyphagous pest that damages over 400 plant species, including commercially grown crops and fruits. It was first described in Taiwan and has since invaded Japan and China. In 2021, B. dorsalis was reported on Jeju Island in the Republic of Korea (ROK). To investigate its origin and understand its colonization pathway in ROK, the genetic characteristics were analyzed by using mitochondrial genes. The study analyzed the haplotypes and genetic differences among populations oriental fruit flies collected from Southeast Aisa, including Thailand, Taiwan, and Vietnam. The mitochondrial genes cytochrome oxidase subunit I (COI) and cytochrome B (CytB) were used for the analysis. The results showed that B. dorsalis had high levels of haplotype diversity among species. No major haplotype was found among populations. The present study enhances our understanding of the haplotype diversity of B. dorsalis in neighboring countries of ROK. This will expand our knowledge of the source of origin and invasive pathway for B. dorsalis.

Bombyx mandarina (Lepidoptera: Bombycidae), the presumed ancestor of the domesticated silkworm B. mori, has long been a subject of study to illustrate the geographic relationships in connection with origin of B. mori. We sequenced 100 mitochondrial genomes of B. mandarina collected from South Korea and Japan and these were combined with public data. Phylogenetic and population genetic analyses showed that all individuals collected in South Korea, except one individual from Inje, formed a strong group together with northern China and some individuals of southern China. This group was placed as the sister group to B. mori strains, suggesting that this group could have been served as an immediate progenitor for B. mori. For further robust inference more analysis is underway.

Although insects lack the adaptive immunity characteristic of vertebrates, certain species exhibit enhanced subsequent immune responses upon re-encountering a pathogen, a phenomenon known as immune priming. The underlying mechanism of this phenomenon is still elusive. This study evaluated the immune priming of the diamondback moth, Plutella xylostella, induced by a nonpathogenic and commensal bacterium, Bacillus subtilis. Prior exposure of P. xylostella to B. subtilis significantly increased survival against a pathogenic bacterium, Bacillus thuringiensis, compared to larvae without pre-exposure. To extend the effect of the microbial commensals, two antibiotics, ampicillin and kanamycin, were treated to suppress their populations. In the axenic-like condition in the gut, cellular and humoral immune responses were significantly suppressed. An addition of B. subtilis to the diet of P. xylostella significantly enhanced the immune responses. Apolipoprotein D, known as a lipid carrier, acts like a vertebrate lipocalin in the immune priming of the other insect, Spodoptera exigua. The ortholog of this gene has been identified in P. xylostella, and its expression was induced upon B. subtilis treatment. This study sheds light on the potential role of commensal gut microbes, including B. subtilis, in the immune priming of these insects.

RNA interference (RNAi) has been applied to control insect pests using gene silencing machinery in which small interfering RNA derived from dsRNA specifically degrades target mRNA. This study optimized dsRNA insecticide specific to thrips infecting hot peppers. Among potent candidate target genes, vATPase B was chosen because its RNAi was highly efficient as much as Snf7, a well-known RNAi target gene. Although RNAi specific vATPase B is lethal to Frankliniella occidentalis, it was not much effective to control other thrips species such as F. intonsa and Thrips tabaci. To expand its target spectrum, we devised a mixture treatment of dsRNA specific to individual species. As expected, each dsRNA was highly efficient in a species-specific manner. This supported the hypothesis of 21mer identity for the efficient RNAi. However, the dsRNA mixture efficiently killed the three thrips species in a crop field. To further expand its spectrum to the whitefly, Bemisia tabaci, we applied virus-induced gene silencing (VIGS) to produce dsRNA in the hot peppers using Tobacco Rattle Virus. VIGS successfully suppressed control gene. dsRNA produced by VIGS gave significnat mortality to B. tabaci in addition to the thrips. These results suggest a technique to expand dsRNA insecticide spectrum using a mixture treatment and VIGS in insect pest control_.

Xenorhabdus와 Photorhabdus 속은 각각 곤충병원성 선충인 Steinernema와 Heterorhabditis에 공생하는 공생세 균이다. 감염성 선충의 유충은 공생세균을 표적 곤충의 혈강에 전달하고, 여기서 세균이 증식하여 숙주 선충의 발달을 돕는다. 이러한 선충과 세균 복합체의 성공적 공생관계는 세균의 이차대사산물을 통한 숙주의 면역억제 에 달려져 있다고 알려져 있다. 본 연구에서는 서로 다른 살충력을 보이는 6종의 Xenorhabdus를 확보하고 이러한 차이가 세균의 성장속도와 NRPS (Non ribosomal peptide synthease)에 의해 생성되는 세균의 이차대사산물 발현에 서 기원한다는 것을 확인하였다. 서로 다른 균주들은 콩명나방 (Tenebrio molitor)에 대한 살충력에 차이를 가지고 있었다. 이러한 세균들은 TSB 배지에서는 세균 성장 속도에 차이가 존재하지 않았지만 콩명나방 혈강 내에서는 세균의 성장 속도에 차이가 존재하는 것으로 나타났다. 또한 각 세균의 이차대사산물 추출물을 통한 곤충의 면역 억제 실험 결과 PLA2 활성 억제, 세포독성 능력들이 살충력과 상관관계가 있는 것으로 나타났다. 이러한 이차대 사산물의 경우 많은 물질이NRPS (Non ribosomal peptide synthease)에 의해 생성되므로 각 세균 별 NRPS의 유전자 발현을 보았을 때 흥미롭게도 살충력이 더 높은 스트레인의 세균이 일부 NRPS 유전자의 발현이 더 높은 것으로 나타났다. NRPS에 의해 합성되는 물질을 포함한 세균의 이차대사산물의 차이를 서로 비교하기 위하여 이차대사 산물 추출액을 GC-MS/MS를 이용하여 분석하였다. 본 연구를 통해 곤충병원세균에 살충력의 기원이 NRPS를 통해 합성되는 이차대사산물에 있다는 것을 확인하였으며 이를 이용한 다양한 NRPS 유래 물질 연구는 신규 살충 물질 개발에 들어가는 비용과 시간을 획기적으로 줄일 수 있을 것으로 기대된다.

식물에 전기장을 처리하면 식물의 생장속도가 빨라지거나 영양학적으로 긍정적인 변화가 생긴다고 알려져 있다. 최근 음이온 처리 시 식물에 전기장을 처리한 것과 유사한 효과가 나타난다고 보고되었고 본 연구에서는 이러한 음이온을 온실해충인 점박이응애와 목화진딧물에 처리하여 방제효과 여부를 확인하였다. 그 결과 음이 온 처리 시 점박이응애와 목화진딧물에서 살충효과와 기피효과가 나타났다. 또한, 점박이응애 알에서도 음이온 처리가 부화율에 영향을 주는 것을 확인할 수 있었다. 이러한 시험 결과를 바탕으로 온실에서 밀도실험 결과, 700,000 ion/cm3 농도에서 무처리구에 비해 밀도가 감소함을 확인할 수 있었다. 따라서, 본 연구는 음이온 처리 시, 부가적인 효과로 온실해충(점박이응애, 목화진딧물)에 대해 친환경적 방제 가능성을 보여준다.

담배가루이는 전세계의 온대 및 아열대 지방에 넓게 분포하고 있으며, 한국에서는 시설재배작물의 주요 해충 이다. 1998년 충북 친천군 장미재배지에서 처음 확인되었으며, 이후 전국적으로 확산된 것으로 추정된다. 담배가 루이는 고추, 토마토, 오이 등 300종이 넘는 넓은 기주범위를 가지며, 식물체를 흡즙하여 작물의 생산성을 저하시 키고 토마토황화잎말림바이러스(tomato yellow leaf curl virus, TYLCV) 등 100여종이 넘는 바이러스를 매개한다. 담배가루이는 주로 살충제를 이용한 방제가 이루어진다. 하지만 살충제를 이용한 방제법은 살충제 저항성 개체 를 발생시킨다. 살충제 저항성 개체가 발생하게 되면 방제 효율이 급감하여 농가에 추가적인 경제적 피해를 야기 한다. 본 연구는 국내 지역별 담배가루이를 대상으로 약제별 살충제 저항성의 발생 현황을 조사하여, 지역별 효과적인 약제를 탐색하고 향후 방제 전략 수립에 기여하고자 한다. 담배가루이는 전국 15지역(파주, 양평, 화성, 양구, 횡성, 평창, 당진, 천안, 공주, 예천, 구미, 사천, 남원, 나주, 고흥)에서 채집되었다. 살충제는 작용기작 별 사용량이 많은 8종을 선정하였으며, 엽침지법을 사용하여 살충률을 확인하였다. 곤충생장조절제(insect growth regulators, IGR) 피리프록시펜계 약제는 알을 대상으로, 그 외 7개 약제는 2령약충을 대상으로 살충률을 확인하였 다. 모든 지역에서 높은 살충력을 보인 약제는 아버멕틴과 밀베마이신계, 스피노신계, METI살충제, 디아마이드 계 약제이다. 특히 아버멕틴과 밀베마이신계 약제는 살충제 권장사용농도(10ppm)보다 낮은 8.9ppm이하의 LC90 값을 보여 감수성으로 추정되며, 예외적으로 천안 지역의 25.6ppm으로 상대적으로 높은 LC90값을 보였다. 낮은 살충력을 보인 약제는 네오니코티노이드계, 설폭시민계, 피리프록시펜계, 테트론산 및 테트람산 유도체 약제이 다 특히 네오니코티노이드계 약제는 모든 지역에서 살충제 권장사용농도(50ppm)보다 높은 715ppm이상의 LC90 값을 보여, 모든 지역에서 살충제 저항성이 발생한 것으로 추정된다. 실험결과를 통해 살충제 별 살충력의 차이와 지역별 살충제 저항성을 검정하였다. 연구결과를 통해 지역별/약제별 저항성관리 및 대응전략을 수립하여 농업 생산성을 향상시키는 것에 도움이 되고자 한다.

The small brown planthopper (SBPH), Laodelphax striatellus, is a major insect pest for the rice plants. SBPH is also a known vector of rice stripe virus (RSV), which causes severe yield losses in rice crops throughout the East Asia. RSV is persistently transmitted by SBPH and can also be transmitted to offspring through transovarial transmission. SBPH is known to migrate from China to the west coast of the Republic of Korea (ROK). The study investigated the impact of temperature on the acquisition and transmission of RSV by SBPH in ROK, which is expected to experience increased migration and emergence of SBPH due to climate change. The results revealed that the acquisition and transmission rates of RSV were higher at 27°C compared to 24°C, with rates of 100% and 78.3%, respectively. However, at 30°C, the acquisition and transmission rates of RSV was decreased. The results suggests that temperature can impact the transmission of RSV by SBPH. To investigate this further, SBPH adults were fed on RSV-infected plants and infection rates were compared across various tissues, including the head, salivary glands, midgut, Malpighian tubules, ovary, and hindgut. Results showed that at 36 hours post-infection, RSV was highly detected in the Malpighian tubules, ovary, and hindgut. At 48 hours post-infection, RSV was also detected in the thorax. These results suggest that the transmission rates of RSV in SBPH increase with temperature between 24-27°C, but decrease at 30°C, indicating that the vectorial capacity of SBPH for RSV decreases above a certain threshold.

Spodoptera eridania and S. ornithogalli (Lepidoptera: Noctuidae), which are polyphagous pests that damage various crops such as tomatoes and beans are regulated quarantine species that are highly likely to invade South Korea. Therefore, it is crucial to promptly and accurately identify the presence of S. eridania and S. ornithogalli in crop fields to effectively eradicate as a regulated quarantine species. In this study, we developed a loop-mediated isothermal amplification (LAMP) assay, which allows for rapid in-field identification. To develop the LAMP　assay, we selected target species-specific genomic regions from the whole-genome sequences of one target and 13 other lepidopteran species. We validated each five and six primer sets that consistently produced positive reactions in S. eridania and S. ornithogalli, respectively. To test the sensitivity of the each locus, LAMP reactions were performed using various reaction times using crude DNA, which was extracted from various types of adult tissues. All sensitivity tests were also successful.

Two-spotted spider mite (Tetranychus urticae Koch; TSSM) is an agriculturally serious pest tat has acquired strong resistance against acaricide. Alternatively, mite-pathogenic fungi could be used to control the mites. The spider mite has symbiotic microorganisms which could be involved in the physiological and ecological adaption to biotic stress. In this study, mite-pathogenic fungi were used to control female adults, and the change of microbiome in the fungus-infected mites was analyzed. The acaricidal activity of fungal isolates was tested, and Akanthomyces attenuatus JEF-147 with the highest acaricidal activity was determined, followed by semi-field assay. Microbiome in the female adults which was infected by A. attenuatus JEF-147 was analyzed, and composition of microorganism was changed by fungal treatment. In bacteria abundance, the arthropod defense-related Rickettsia increased, but reproduction-associated Wolbachia decreased. The change in major bacterial abundance in the infected mites could be explained by the trade-off between reproduction and immunity. This work describes that a possible trade-off in arthropods against fungal pathogens could be predicted by the microbiome analysis.

Climate change has led to increased insect pests and pest distribution changes. Traditionally, chemical control using synthetic pesticides has been the main method for pest management, but the emergence of pesticide-resistant pests has become a problem. There is a need to develop new pest control agents to overcome these issues. Entomopathogenic fungi used in pest management have minimal environmental side effects and possess a mechanism of action distinct from that of synthetic pesticides. However, there is a need for the development of technologies to maximize the insecticidal effects of fungi against pests, and expressing and releasing dsRNA within the fungi can preemptively knock out the activation of the insect’s defense system, thereby enhancing the insecticidal effect. Controlling insect defense genes and using entomopathogenic fungi as bio-carriers forms a new pest management strategy. This approach, described as a “microbial insecticide agents development strategy of cassette concept, ” can versatilely modify genes and microbes. It is expected to overcome the limitations of synthetic pesticides.

Upon immune challenge, recognition signals trigger insect immunity to remove the pathogens through cellular and humoral responses. Various immune mediators propagate the immune signals to nearby tissues, in which polyunsaturated fatty acid (PUFA) derivatives play crucial roles. However, little was known on how the insects terminate the activated immune responses after pathogen neutralization. Interestingly, C20 PUFA was detected at the early infection stage and later C18 PUFAs were induced in a lepidopteran insect, Spodoptera exigua. This study showed the role of epoxyoctadecamonoenoic acids (EpOMEs) in the immune resolution at the late infection stage to quench the excessive and unnecessary immune responses. In contrast, dihydroxy-octadecamonoenoates (DiHOMEs) were the hydrolyzed and inactive forms of EpOMEs. The hydrolysis is catalyzed by soluble epoxide hydrolase (sEH). Inhibitors specific to sEH mimicked the immunosuppression induced by EpOMEs. Furthermore, the inhibitor treatments significantly enhanced the bacterial virulence of Bacillus thuringiensis against S. exigua. This study proposes a negative control of the immune responses using EpOME/DiHOME in insects.

Over the last decade, there has been growing interest in the plastic degradation capabilities of insect because herbivorous insects may be a valuable resource for microorganisms that can break down synthetic plastics. Insects that can digest plastics using their gut microbiota are gaining interest for use in bioremediation, although their environmental benefits remain unknown. However, most plastics biodegraded by insect gut microbes are polyethylene, polystyrene with little knowledge available on the gut microbiome of insects capable of degrading other synthetic plastics. Therefore, there is an urgent need to secure microbial resources based on insect-microbiome interactions and promote end-of-life solutions for synthetic plastics.