Antiviral Treatment Reveals a Cooperative Pathogenicity of Baculovirus and Iflavirus in Spodoptera exigua, a Lepidopteran Insect

( Miltan Chandra Roy ),( Shabbir Ahmed ),( Md. Mahi Imam Mollah ),( Yonggyun Kim ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.4

The beet armyworm, Spodoptera exigua, is a serious insect pest infesting various vegetable crops. Two infectious insect viruses, baculovirus and iflavirus, are known to induce epizootics in S. exigua populations. Indeed, some laboratory colonies have appeared to be covertly infected by these viruses. Diagnostic PCR tests detected two different viruses: Spodoptera exigua multiple nucleopolyhedrosis virus (SeMNPV) and iflaviruses (SeIfV1 and SeIfV2). Viral extract from dead larvae of S. exigua could infect Sf9 cells and produce occlusion bodies (OBs). Feeding OBs to asymptomatic larvae of S. exigua caused significant viral disease. Interestingly, both SeIfV1 and SeIfV2 increased their titers at late larval stages. Sterilization of laid eggs with 1% sodium hypochloride significantly reduced SeMNPV titers and increased larval survival rate. Doublestranded RNA (dsRNA) specific to SeIfV1 or SeIfV2 significantly reduced viral titers and increased larval survival rate. To continuously feed dsRNA, a recombinant Escherichia coli HT115 expressing SeIfV1-dsRNA was constructed with an L4440 expression vector. Adding this recombinant E. coli to the artificial diet significantly reduced the SeIfV1 titer and increased larval survival. These results indicate that laboratory colony collapse of S. exigua is induced by multiple viral infections. In addition, either suppression of SeMNPV or SeIfV infection significantly increased larval survival, suggesting a cooperative pathogenicity between baculovirus and iflavirus against S. exigua.

Joint toxicity of methoxyfenozide and lufenuron on larvae of Spodoptera exigua Hübner (Lepidoptera: Noctuidae)

Jixiang Chen,Weili Jiang,Hongyan Hu,Xiaoyan Ma,Qian Li,Xianpeng Song,Xiangliang Ren,Yan Ma 한국응용곤충학회 2019 Journal of Asia-Pacific Entomology Vol.22 No.3

The joint action and sublethal effects of methoxyfenozide and lufenuron were measured against Spodoptera exigua. Methoxyfenozide and lufenuron exhibited optimum synergistic toxicity on S. exigua at a mass ratio of 4:6, and the co-toxicity coefficient (CTC) was 165.705. Third instars larvae of S. exigua were treated with methoxyfenozide (LC 15 = 21.004 ng/cm 2 ), lufenuron (LC 15 = 27.134 ng/cm 2 ), or a mixture of methoxyfenozide and lufenuron (MML, LC 15 = 16.503 ng/cm 2 ) through feeding for 72 h. Ingestion of MML by larvae significantly inhibited larval and pupal weights and pupation rate, and prolonged the larval and pupal development of S. exigua compared to individual treatment ofmethoxyfenozide or lufenuron. Both methoxyfenozide and MML treatments significantly decreased the fertility of female S. exigua. No significant changes were observed in case of adult emergence and egg hatching for different treatments. The MML-treated S. exigua exhibited significantly lower activities of polyphenol oxidase (PPO) and cytochrome P450 (CYP450) than those in S. exigua treated separately with methoxyfenozide or lufenuron. Finally, methoxyfenozide, lufenuron, and MML treatments decreased chitinase, acetylcholinesterase (AChE), carboxylesterase (CarE), and glutathione-s-transferase (GST) activities in S. exigua.

Antifeedant Activity of Essential Oils and Its Constituents to Spodoptera litura and Spodoptera exigua

Jun-Ran Kim,Sang-Guei Lee 한국응용곤충학회 2014 한국응용곤충학회 학술대회논문집 Vol.2014 No.04

The antifeedant activity of 20 plant essential oils, constituents from clove stem oil and related compounds were tested against the third instar larvae from both moth Spodoptera litura and Spodoptera exigua by used leaf dipping bioassay. Among the oils tested, clove stem (94%), thyme oil red (85%), and savory oil (80%) were showed high antifeedant activity against both S. litura and S. exigua third instar larvae. Thyme oil white (91%), geranium (90%), and cinnamon bark oil (85%) were shown high antifeedant activity against only S. exigua when compare other oils. The other plant essential oils were showed moderate (40-50%) or low (>20%) antifeedant activity against third instar larvae of both S. litura and S. exigua. The most active clove stem oil constituents were indentified by GC-MS. The major constituents eugenol (95%), farnesene (81%) and structurally related compounds isoeugenol (96%), nerolidol (80%) were showed significant antifeedant activity against both S. litura and S. exigua. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the essential oils and their constituents describes as potential insecticides for the control of moth population with antifeedant activity.

RNA Interference of Glycerol Production Patterns a Rapid Cold Hardiness of the Beet Armyworm, Spodoptera exigua

Youngjin Park,Yonggyun Kim 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.04

The beet armyworm, Spodoptera exigua, is a freeze-susceptible species and overwinters without diapause in temperate zone. Depression of supercooling point (SCP) and rapid cold hardiness (RCH) allow S. exigua to survive at low temperatures. This study reports a polyol which is responsible for the cold hardiness of S. exigua. Pre-exposure of S. exigua larvae to 4°C for 6 h significantly enhanced survival under a freezing temperature (-10°C). This pre-exposure treatment also significantly depressed larval SCPs. Analysis of polyols indicated that glycerol titers significantly increase with increase of pre-exposure time. Glycerol kinase (GK) and glycerol-3-phosphate dehydrogenase (GPDH) are involved in glycolysis pathway of insect. The S. exigua GK (SeGK1) and G3PDH (SeG3PDH1) genes were predicted from 454 pyrosequencing transcripts from fifth instar larvae of the beet armyworm, S. exigua. The SeGK1 and SeG3PDH1 genes both were expressed in all larval stage by RT-PCR analysis. Expression of SeGK1 and SeG3PDH1 genes were suppressed by its specific dsRNASeGK1 or dsRNASeG3PDH1 injection into hemocoel of 5th instar larva. Each 200 ng of dsRNASeGK1 or dsRNASeG3PDH1 injection also significantly decreased glycerol amount in hemolymph. Larval treated by either dsRNASeGK1 or dsRNASeG3PDH1 significantly lost the RCH under -10°C exposure. These results indicate that glycerol is a crucial RCH agent and its synthesis is regulated by SeGK1 and SeG3PDH1 genes in S. exigua.

유기재배 배추포장 내 파밤나방에 대한 곤충병원성 미생물의 방제효과

박종호,홍성준,한은정,심창기,김민정,김용기 한국유기농업학회 2015 韓國有機農業學會誌 Vol.23 No.4

This study was carried out to identify the control effect of entomopathogenic microagent against Spodoptera exigua on organic chinese cabbage. In laboratory condition, insecticidal activity of 4 commercial BT pesticides against S. exigua were lower than 10% against second instar S. exigua. The insecticidal activity of entomopathogenic nematode were 33.3%, 83.3% and 100% at the concentration of 1×102, 3×102, 1×103 nematodes/ml, respectively. Mixture of BT and nematode showed growth inhibition against S. exigua larvae. S. exigua nucleopolyhedrovirus (SeNPV) of 105 PIBs/ml showed more than 70% insecticial activity. The yield of SeNPV was increased as in higher initial inoculation concentration of NPV, food supply, and growth temperature increased. In greenhouse experiment, the control value of BT and nematode mixture treatment was higher than BT and nematode treatment alone against S. exigua. In treatment of 107 PIBs/ml of SeNPV, S. exigua was controlled completely. In farm condition, mixture of microbial agent and organic agricultural material showed higher control value against lepidopteran pest including S. exigua than BT single treatment.

Insecticidal Capacity of Recombinant Baculoviruses to Plutella xylostella and Spodoptera exigua larvae

Myung-Pyo Jung,Hong-Hyun Park,Jae Young Choi,Yeon Ho Je 한국응용곤충학회 2012 한국응용곤충학회 학술대회논문집 Vol.2012 No.05

This study was conducted to investigate the insecticidal capacity of recombinant baculoviruses to Plutella xylostella and Spodoptera exigua larvae. For recombinant viruses, Bacillus thuringiensis cry1-5 crystal protein gene was introduced into the genome by fusion of polyhedrin-cry1-5 under the control of polyhedrin gene promoter. Recombinant AcPolh5-3006BiKTT and AcPolh5-3006 AvTox2 based on BiKTT and AvTox2, respectively, were constructed under the control of early promoter from Cotesia plutellae bracovirus. Mortality of S. exigua larvae was significantly higher when they fed on cabbage coated with ApEGFP (wild type) over 5.0×106 PIBs/ml. For AcPolh5-3006BiKTT and AcPolh5-3006AvTox2, mortality of P. xylostella and S. exigua larvae was significantly higher when they fed on cabbage coated with recombinant baculoviruses over 5.0×106 PIBs/ml and 1.0×104 PIBs/ml, respectively. The value of LD50 was lower in the treatments with AcPolh5-3006BiKTT (P. xylostella:1.2×106, S. exigua:1.3×104) or AcPolh5-3006AvTox2 (P. xylostella:2.3×106, S. exigua:1.4×104) than the treatments with ApEGFP (P. xylostella: not estimated, S. exigua:5.0×105). Survival time (ST50) of P. sylostella larvae was much shorter at AcPolh5-3006BiKTT (29.6h) than AcPolh5-3006AvTox2 (46.2h) while that of S. exigua larvae was much shorter at AcPolh5-3006AvTox2 (95.1h) than AcPolh5-3006BiKTT (101.9h) or ApEGFp (130.7h). The two recombinant baculoviruses were more effective in S. exigua larvae but slower speed of action.

Visual Preference of Spodoptera exigua to Various Wavelengths of Light Emitting Diodes

Hoi-Seon Lee 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.10

Spodoptera exigua is a significant polyphagous pest in the greenhouse and open field. Our aim of this study was to evaluate light emitting diodes (LEDs) as the potential attractants against Spodoptera exigua on various wavelengths, light intensity, and light duration. The preference response to S. exigua was investigated by the laboratory and field-scale. The wavelengths of LEDs were composed as follows: blue (470 nm), green (520 nm), yellow (590 nm), red (625 nm) and white (450-620 nm). When the optimal light condition was investigated in the laboratory scale, the all light treatments attracted the highest number of S. exigua at 40 lux intensity and 60 min duration. Based on the wavelengths under optimal light condition, the white LED exhibited the highest attraction rate (91.1%), followed by green (88.9%), blue (81.1%), yellow (63.3%) and red (56.7%), respectively. In comparison with the selected white LED and yellow sticky traps in the field-scale, the white LED (81.3%) was about 16.26 times more attractive than yellow sticky trap (5.0%). These results clearly show that the white LED had the greatest attraction against S. exigua.

Insecticidal activity of secondary metabolites from Streptomyces celluloflavus against Spodoptera exigua

Minghui Wang,Jae Young Choi,Dong Hwan Park,Siyi Liu,Yeon Ho Je 한국응용곤충학회 2023 한국응용곤충학회 학술대회논문집 Vol.2023 No.10

The beet armyworm, Spodoptera exigua, is one of the worldwide distributed agricultural pest insects and has been known to show high resistance to conventional chemical insecticides. Since it has been reported that secondary metabolites from actinomycetes show insecticidal activities against various insect pests, actinomycetes could be a potential source of insecticidal compounds. In this study, culture extracts of Streptomyces strains were tested for their insecticidal activity against Spodoptera exigua. Among them, culture extracts of IMBL-0003 strain which was identified as Streptomyces celluloflavus showed a high insecticidal activity (more than 90% mortality). These results suggested that secondary metabolites of this isolate could have potentials to be a efficient eco-friendly pesticide for controling Spodoptera exigua.

Exaptation of I4760M mutation in ryanodine receptor of Spodoptera exigua (Lepidoptera: Noctuidae): Lessons from museum and field samples

Changhee Han,Md-Mafizur Rahman,Jiyeong Shin,Juil Kim 한국응용곤충학회 2023 한국응용곤충학회 학술대회논문집 Vol.2023 No.10

Since 2007, diamide insecticides have been widely used in Korea to control various types of lepidopteran pests including Spodoptera exigua. For nearly a decade, diamide resistance in field populations of S. exigua across 18 localities has been monitored using bioassays. Based on the LC50 values, some field populations showed a high level of resistance against chlorantraniliprole, although regional and temporal variations were observed. To investigate resistance at a molecular level, mutations (Y4701C, I4790M, and G4946E) were examined in the ryanodine receptor (RyR), which is the primary mechanism underlying diamide insecticide resistance. As a result, only I4790M mutation was found in most of field populations. As resistance levels varied significantly despite the uniform presence of the I4790M mutation, we considered the presence of another resistance factor. Further, the I4790M mutation was also found in S. exigua specimens collected prior to the commercialization of diamide insecticides in Korea as well as in other countries, such as the USA. This finding led us to hypothesize that the I4790M mutation were predisposed in field populations owing to selection factors other than diamide use. For further clarification, we conducted whole-genome sequencing of S. exigua (449.83 Mb) and re-sequencing of 18 individuals. However, no additional non-synonymous mutations were detected in the RyR-coding region. Therefore, the high level of diamide insecticide resistance in Korean S. exigua is not caused by mutations at the target site, RyR, but is attributed to other factors that need to be investigated in future studies.

Cloning of a scavenger receptor gene from Spodoptera exigua hemocytes

Jong-Ho Park,Jung-A Park,Youngyun Kim 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.05

Scavenger receptors (SRs) are transmembrane cell surface molecules recognized in apophotic cells, bacteria and lipopolysaccharide. With no physiological information on SRs in insects except SR-CI of Drosophila melanogaster, a putative SR gene was cloned and characterized in Spodoptera exigua. A partial S. exigua SR gene was obtained from hemocyte transcripts and exhibited high homology with type C. Its expression was confirmed in all developmental stages. Among different tissues, S. exigua SR was expressed highly in hemocytes. To confirm change in SR expression by infection, Escherichia coli was injected to fifth instar and RNA was extracted after 10 hours. SR expression in hemocytes of E. coli injected larva was not significantly different from the control but SR expression in fat body of E. coli injected larva was higher than the control. It is expected that SRs of S. exigua are related with immune responses against bacteria such as E. coli. To address its function, S. exigua SR expression was suppressed by double-stranded RNA (dsRNA).