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.

Economic injury level and control thresholds for the management of beet army worm, Spodoptera exigua (Lepidoptera: Noctuidae) were evaluated on chinese cabbage of two different planting time. Two inoculation times were tested for each planting and the number of inoculated larva was 10, 20, 40, 80, respectively. Damages of leaves by first inoculation were 63.2% after eight days planting on 80 larva inoculation plot. By the second inoculation, those were below 50% after 20 days planting on the end of September. The linear relationships between population density and yield reduction were as following, Y = -10.62x + 867.9 (R² = 0.643) for 5 days and Y=-6.432x + 1074 (R² = 0.720) for 20 days. Based on these results the economic injury level was 5.4 larva for five days and 9.0 larva for 20 days per 20 chinese cabbage. The control thresholds calculated by 80% level of economic injury level were 4.3 and 7.2 larva, respectively.

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.

For the development of friendly environmental control of the beet armyworm, Spodoptera exigua that is too hard to control in the field, 25 insecticides were chosen from 58 registered to the beet armyworm, and bioassayed. There are 12 insecticides with neurotoxical activities, 10 with insect growth regulators and 3 Bacillus thuringiensis products. Among 12 insecticides with neurotoxical activities, mortality of S. exigua was 100% with emamectin benzoate (EC) and indoxacarb (WP) within 3 and 5 days after application, respectively. Otherwise, WG and SC of indoxacarb, Indoxacarb + etofenprox (WP) and pyridalyl (EW) were showed up to 91%. Methoxyfenozide + spinosad (SC) was better than any other insect growth regulator as 100% mortality within 3 days after application. And methoxyfenozide (WP), tebufenozide (WP) and methoxyfenozide (SC) were 92% by 5 days. However, 3 kinds of B. thuringiensis products were showed under 35% mortality within 5 days from first spray.

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.

파밤나방 핵다각체병바이러스(Spodoptera exigua nucleopolyhedrovirus: SeNPV)의 온도별, 농도별로 병원활성을 조사한 결과는 다음과 같다. SeNPV의 온도에 따른 은 2령 에서는 , 에서는 로 온도가 높아질수록 낮아졌으며, 다른 영기에서도 같은 경향이었다. 에서 SeNPV 의 파밤나방 3령 유충에 대한 은 9.0일이었으나 SeNPV 에서는 6.9일-3.5일로 더 짧았다. 24, 28, 의 SeNPV 에서는 5.7일, 5.5일, 4.9일의 병원 활성을 보여 온도가 올라갈수록 은 짧아졌다. 또한 바이러스 농도가 높고 유충의 영기가 어릴수록 짧아져 은 온도 바이러스 농도, 유충영기에 따라 차이가 있었다.

폴리드나바이러스는 일부 내부기생봉의 공생 바이러스로서 기생봉 기생과정중 피기생자의 면역억제와 발육지연에 중요한 역할을 담당한다. 프루텔고치벌(Cotesia plutellae)유래 브라코바이러스(CpBV)는 피기생자의 발육을 교란시키는 주요 원인자로서 작용하는 폴리드나바이러스의 일종이다. 본 연구는 이 CpBV가 비자연기주에게도 발육교란을 유발할 수 있는 지 조사하였다. 이를 위해 프루텔고치별에 의해 기생되지 않는 비기주인 파밤나방(Spodoptera exigua)을 이용하였다. 이용된 CpBV는 프루델고치벌 난소받침(calyx)추출물에서 얻었다. 이 추출물은 CpBV항체에 대해서 뚜렷한 항원-항체반응성으로 CpBV 보유가 입증되었다. 고치벌 암컷 한 마리 CpBV 추출물을 후기 4령의 파밤나방 혈강내로 주입시켰다. CpBV 주입된 파밤나방 유충은 유충기간이 연장되고, 체중증가 가 억제되며, 궁극적으로 변태가 억제되었다. 이러한 CpBV의 발육억제 효과는 이 바이러스의 항체를 함께 주입하여 줌으로 해소되었다. 여기서 항체 단독으로는 파방나방 유충 발육에 아무런 영향을 주지 않았다. 이 결과는 CpBV가 공생 기생봉의 비기주체에 대해서 발육교란 효과를 줄 수 있다는 것을 제시하고 있다.