고주파 처리는 파밤나방(Spodoptera exigua)의 생리변화를 유발시켜 섭식행동, 발육 및 면역반응의 변화를 초래한다. 본 연구는 이러한 고주파의 영향을 파밤나방의 생화학적 변화를 통해 분석했다. 고주파(5,000 Hz, 95 dB) 처리는 중장 상피세포의 단백질 합성과 분비를 억제시켰다. 또한 이 고주파 처리는 중장의 인지질분해(phospholipase ) 소화효소의 활성을 현격하게 억제시켰다. 고주파 처리는 세 종류의 열충격단백질과 지질운송단백질(apolipophorin III)의 유전자 발현을 변동시켰고 이러한 변화는 중장 조직에서 뚜렷했다. 혈림프 혈장에 존재하는 지질 및 유리당의 함량이 고주파 처리에 의해 현격하게 증가했다. 이러한 결과는 고주파 처리가 파밤나방의 체내 생화학적 변화를 유발시켜 생리적 교란을 유도하는 스트레스로 작용한다는 것을 제시하고 있다.

일부 고주파 음파 처리가 파밤나방(Spodoptera exigua)의 생리변화를 유발시킨다. 이 연구는 초음파( 20 kHz) 처리가 파밤나방 유충 섭식, 용 발육 및 성충 교미행동에 미치는 영향을 분석하였다. 초음파 처리는 5령충의 섭식 활동을 억제시켰다. 특별히 30 kHz 또는 45 kHz 초음파 처리를 받은 유충은 50% 이상의 섭식활동이 감소하였다. 이러한 초음파 처리를 받은 유충은 혈장의 주요 영양물질 함량이 변동되었다. 혈장 단백질은 처리 초음파의 주파수 증가에 따라 감소하였다. 그러나 혈당은 처리 초음파의 주파수 증가에 따라 증가하였다. 지질 함량은 30 kHz 처리까지는 증가하다가 이후 감소하였다. 파밤나방 5령의 혈구, 지방체 및 표피세포의 세 조직은 스트레스 관련 유전자들인 세 종류의 열충격단백질과 apolipophorin III를 발현시켰다. 그러나 초음파를 처리할 경우 일부 스트레스 관련 유전자들의 발현을 크게 억제시켰다. 초음파 처리는 또한 용발육을 억제시켜, 용기간을 연장시키고 성충으로 우화를 현격하게 낮추었다. 끝으로 초음파 처리는 성충의 교미행동을 억제시켜 암컷의 산란력을 뚜렷하게 낮추었다. 이러한 결과는 초음파가 파밤나방의 생리적 스트레스로 작용하고 있다는 것을 제시하고 있다.

The aim of this study is to observe the attraction of four colored lights against beet armyworm (Spodoptera exigua). The visual preference of the beet armyworm for light-emitting diodes (LEDs) was examined by LED equipped phototactic chamber in the dark room at 27 ± 0.5°C and 60 ± 5% relative humidity. Evaluated specific wavelengths of LEDs were blue (470 ± 10 nm), green (520 ± 5 nm), yellow (590 ± 5 nm) and red (625 ± 10 nm), and compared with that of the commonly luring lamp used fluorescent (380-800 nm) which served as controls. The light intensity was tested at 20, 40, 60, 80 and 100 lx, and light-exposure time was determined at 20, 40, 60, 80 and 100 min. All of the light treatments with 40 lx intensity and the 60 min light-exposure time showed the highest attraction rate to S. exigua. Based on attraction rate of the green LED (88.9%) was the most attractive to S. exigua, followed by blue LED (81.1%), yellow LED (63.3%) and red LED (56.7%). In comparisons with LED and fluorescent light, the attractive rate to green LED against beet worm was more effective than that of fluorescent (80%) light. Overall, these results indicated that the eco-friendly LED could be a more effective substitute for the chemical free insect pest control system because of the various advantages.

Ten novel microsatellite loci were isolated and characterized from the beet armyworm, Spodoptera exiqua. The isolated loci are polymorphic, with 2~12 alleles in 18 individuals from several populations in Korea. All 18 individuals had different multilocus genotypes with heterozygosity ranging from 0.089 to 0.843. Nine of 10 loci kept the Hardy-Weinberg equilibrium in adjusted significance thresholds. We report the development of microsatellite markers for S. exiqua potentially suitable for further studies of population structure, dispersal, and host relationship.

Antimicrobial peptides (AMPs) are a group of immune proteins that protect the host from microial infection. Gallerimycin is one of the AMPs most commonly found in Galleria mellonella and Spodoptera frugiperda. In this paper, we found Gallereimycin in Spodoptera exigua by expressed sequence tag library 0analysis. The gallerimycin of S. exigua gene is 332 bp long and the predicted open reading frame contains 75 amino acids with a signal peptide. After removing signal peptide, S. exigua gallrimycin was estimated to be 5.9 kDa and pI at 8.53. The gallerimycin of S. exigua shared maximum sequence homology with that of S. frugiperda. In naive S. exigua larvae, not much gene expression was detected, but strongly induced in fat body and hemocytes following immune challenge with entomopathogenic bacteria and fungus. A recombinant gallerimycin was prepared using a bacterial expression system and showed significant antibacterial and antifungal activities. RNA interference using double stranded RNA could knock down the expression of gallerimycin and significantly suppressed immune capacity.

To clarify the molecular mechanism of metamorphosis, we analyzed the Broad-Complex (BR-C) gene in the beet armyworm, Spodoptera exigua. We obtained a partial BR-C sequence from a pyrosequencing cDNA library. The BR-C of S. exigua was expressed only in the final larval instar, at which its expression was clearly detected in the epidermis. A treatment of a juvenile hormone analog, pyriproxyfen, inhibited larval-pupal metamorphosis and suppressed the BR-C expression. The hormonal treatment also inhibited expression of two storage protein genes that were usually expressed during a final larval instar. RNA interference of the BR-C using its double strand RNA suppressed BR-C expression and inhibited the larval-pupal metamorphosis. These results suggest that the BR-C is critical to induce larval-pupal metamorphosis of S. exigua.

14-3-3 proteins are known to play a pivotal role in a diverse array of cellular events such as cell survival, apoptosis, and signal transduction. Numerous 14-3-3 ζ have been cloned and characterized from a host of eukaryotic organisms including human, plants, yeast, fruit fly and silkworm. However, no study on Spodoptera exigua 14-3-3ζ in conjunction with virus infection has so far been reported in insects. It appears that expression of Se14-3-3ζ was decreased starting 24 h post-SeNPV infection as SeNPV titers seemed to increase as evidenced by intense bands of SeNPV IAP3. Interestingly, confocal microscopic analysis revealed that Se14-3-3ζ is expressed at the apical side of the NPV-uninfected gut cells, whereas it was detected mainly in the nucleus of the NPV-infected cells. Thus, despite the biological significance of Se14-3-3ζ in S. exigua in conjunction with molecular interactions between SeNPV and S. exigua is unclear now, our data suggest that Se14-3-3 ζ protein plays a role to protect S. exigua from the infection or inhibit replication of SeNPV.

Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway is known to play a pivotal role in various cellular events and antiviral responses in both vertebrates and insects. In an attempt to elucidate the potential involvement of STAT on S. exigua-SeNPV interactions, the full length cDNA of SeSTAT was cloned from S. exigua. Analysis of temporal expression patterns shows that SeSTAT is expressed in all stages of life cycle such as larvae, pupae, and adult. Spatial expression analysis shows that it is highly expressed in fat body and Malpighian tubule. Interestingly, SeSTAT is induced at 24 h in response to either laminarin or LTA injection in larvae. Electrophoretic mobility shift assay (EMSA) shows that the binding of nuclear extracts from fat body cells immune-challenged with LTA to STAT5 probe was observed. In addition, SeSTAT was nuclear-translocalized in both fat body and gut cells that were challenged with LTA and laminarin, respectively. Finally, gene silencing of SeSTAT shows that SeNPV number appears to be increased. It suggests that SeSTAT may act as a negative regulator against SeNPV in midgut.

For the environment-friendly control of beet armyworm, Spodoptera exigua, in spring onion fields, we have examined an alternative application method. Twenty-five insecticides registered for spring onion were tested for control effect against the beet armyworm in the laboratory, then the best 9 chemical and a single biological insecticides were selected and compared with 2 new isolates of Bacillus thuringiensis in a polyvinyl house. After that, 4 chemical and 3 B. thuringiensis treatments were used in the field for the control of beet armyworm in the spring onion. Two application methods are used: one is triple treatments with the same chemical and the other is alternative application with different chemicals and B. thuringiensis for 7 days intervals. Indoxacarb WP – chlorfluazuron EC – B.t. var. kurstaki CAB141 and indoxacarb WP – methoxyfenozide + spinosad SC – Chlorfluazuron EC – B.t. var. aizawai CAB109, B.t. var. kurstaki CAB141 showed greater than 78% mortality of beet armyworm larvae and greater than 43% damage decrease in spring onions infested by beet armyworm. These results showed that alternative applications had higher control effect than any other applications. It was suggested that alternative applications with microbial biological agents such as B. thuringiensis might minimize the development of insecticide resistance and might be used as the environment-friendly control of the beet armyworm.

Two biogenic monoamines, octopamine and 5-hydroxytryptamine (5-HT), are known to play immune mediators in insects. They induce hemocyte behaviors by stimulating cytoskeleton rearrangement. However,it is not clear how they activate the hemocytes in terms of intracellular signal transduction. This study analyzed their interactions with signal pathways implicated in nodule formation via eicosanoids or hemocyte locomotory behavior via a small GTPase. Both octopamine and 5-HT increased hemocytic nodule formation in response to bacterial challenge in the beet armyworm, Spodoptera exigua. However, their immune mediation was inhibited by a treatment of dexamethasone (a specific inhibitor to phospholipase A2). In the presence of phentolamine (a specific antoganist to octopamine) or ketanserin (a specific antoganist to 5-HT), the inhibitory activity of dexamethasone was rescued by adding arachidonic acid (a precursor of eicosanoid biosynthesis). These results suggest that the mediation of nodule formation by the two monoamines is followed by eicosanoid signaling. Two monoamines also induced up-regulation of circulating hemocyte counts in S. exigua. This increase of hemocyte counts was not explained by de novo production of hemopoietic organ because even ligation between thorax and abdomenin order to block hemolymph circulation did not inhibit the increase of circulating hemocyte counts by octopamine.A small GTPase, Rac1, appeared to be involved in this hemocyte mobilization from a sessile compartment in S. exigua. Inhibition of Rac1 activity significantly suppressed hemocyte spreading behavior and the hemocyte mobilization. In summary, octopamine and 5-HT mediate cellular immune responses of S. exigua via eicosanoid signal or independently by activating Rac1 following increase of cAMP in the hemocytes.

A monoterpenoid, benzylideneacetone (BZA), is synthesized by an entomopathogenic bacterium, Xenorhabdus nematophila K1, and known to suppress insect immune responses by inhibiting phospholipase A2(PLA2). This was designed to test its effect of insect digestion by oral administration. The beet armyworm, Spodoptera exigua, was tested by treating its artificial diet with different doses of BZA. The second instar larval were treated with the diets and monitored in their pupation, pupal weight, and adult emergence. BZA gave significant adverse effects on the larval development and subsequent adult metamorphosis. Digestive lumen of the fifth instar larval of S. exigua possessed activity, which was significant inhibited by BZA. These results support that BZA can be developed as a novel feeding deterrent.

The Welsh onion beet armyworm, Spodoptera exigua (Hübner), has attacked Welsh onion and is now the most important pest of Welsh onion in southwestern Korea. The beet armyworm has a wide host range, occurring as a serious pest of vegetable and fields. The relatively high abundance of beet armyworm has stimulated frequent application of insecticides to foliage. Insecticide resistance is a major problem in management of this insect. Accordingly, pesticide application for the control of beet armyworm was tried in both the open field and in laboratory, using 4 synthetic compounds such as metaflumizone and chlorfenapyr, indoxacarb, flufenoxuron, emamectin benzoate. In the laboratory, each developmental stages from eggs, larva to pupa was tested against 4 insecticides. Against the eggs of welsh onion beet armyworm, there was no significantly different with each other. These tested chemicals no killing effect to eggs. However, the population of 1st larva hatched from eggs were reduced because they eaten the egg shell with residual insecticides. The tested insecticides were taken very high mortalities to 1st to 3rd larva of Welsh onion beet armyworm. Otherwise, there were decreased the death rate from 4th to 6th larva. On the other hand, their value of control effects were relatively good against Welsh onion beet armyworms in the field between 87.2 and 90.5% on 10 days after insecticide application.

Monoamines have been known to mediate cellular immune responses such as hemocyte nodulation and phagocytosis in some insects. Eicosanoids also mediate the cellular immune reactions responsible for clearing bacterial infection from hemolymph circulation in various insects. In this study, we investigated a functional relationship of both mediators in expressing hemocyte nodulation and phagocytosis of fifth instar larvae of the beet armyworm, Spodoptera exigua. Addition of octopamine or serotonin along with bacteria enhanced hemocyte nodulation and phagocytosis of S. exigua larvae. Phentolamine (octopamine inhibitor) and ketanserin (serotonin inhibitor) suppressed hemocyte nodulation and phagocytosis of S. exigua in response to a bacterial challenge. Each inhibitory effect of both monoamine inhibitors was recovered by addition of either octopamine or serotonin, suggesting their independent signaling pathways. Both inhibitor effects were also recovered by addition of arachidonic acid (a precursor of eicosanoid biosynthesis). Furthermore, the stimulatory effects of monoamines on the cellular immune responses were prevented by addition of dexamethasone (a specific phospholipase A2). However, the inhibitory effect of dexamethasone was not recovered by excess amounts of monoamines. These results suggest that monoamines mediate hemocyte nodulation and phagocytosis through a downstream eicosanoid signal pathway in S. exigua.

Control thresholds for the management of beet army worm, Spodoptera exigua (Lepidoptera : Noctuidae) were evaluated on welsh onion of two different planting time. Two inoculation times were tested for each planting and the number of inoculated larva was 5, 10, 20, 40 per twenty plants. The injured rate of leaves was 33.5% to 10.9% at 7th September at 40 to 5 larva inoculation plot on the five days planting. That of leaves was 20.5% at 40 larva on the twenty days planting. The yields of welsh onion on non-inoculation plot were 4,395 ㎏ per 10a. The rate of reduced yields was 49.2%(1,774.2 ㎏) and 36.5%(2,220.5 ㎏) at 40 larva inoculation on the 5 and 20 days planting, respectively. The linear relationships between population density and yield reduction were as following, it was Y=-43.474X + 3419.6 (R² = 0.9698) for 5 days and Y=-32.977X + 3518.9 (R² = 0.9928) for 20 days. Based on these results the control threshold level was estimated to be 1.8 larva for 5 days and 4.6 larva for 20 days per 20 plant. The more damaged leaves by S. exigua larva, the more yield reduction on welsh onion.