• Korean journal of applied entomology
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• v.46 no.1 s.145
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• pp.27-35
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• 2007

Seasonal occurrences of tobacco cutworm, Spodoptera litura and beet armyworm, Spodoptera exigua were observed using sex pheromone traps at different locations and climatic regions in Yeongnam district. In Gyeongnam province, S. litura male adults kept occur from mid or late March to mid or late November Whereas in Gyeongbuk province, S. litura occurred from mid or late April to early or mid November with exception at Uljin where it was late May to late October. According to the climatic regions, the peak occurrence of S. litura was middle September at the southern coast region, late August at the inland and the basin region, middle August at the inland mountainous region, and early September at the eastern middle coast region. The occurrence rate of S. litura was the highest at Jinju with 20.0% and the lowest at Changyeong with 8.6% in Cyeongnam province, while it was the highest at Sungju with 3.3% and the lowest at Uljin with 0.8% in Gyeongbuk province. In accordance with the climatic regions, the occurrence rate of S. litura was the highest at the inland region with 43.7%, and followed by the southern coast region (36.3%), the basin region (8.4%) and the inland mountainous region (7.0%), and was the lowest at the eastern middle coast legion with 4.6%. On the other hand, S. exigua occurred from early March to middle November with the exception of the eastern middle coast region including Pohang, Yeongdeog and U]ien in Cyeongbuk province where it occurred from mfd April to middle November. The peak occurrence of s. exigua was early August at the inland region, the basin region and the inland mountainous region, and was late of August at the southern coast region and the eastern middle coast region. The occurrence of S. exigua was the highest at Changyeong with 1.6% and the lowest at Busan with 0.4% in Gyeongnam province, while it was the highest at Sungju with 37.2% and the lowest at Uljin with 2.7% in Gyeongbuk province. The climatic regional occurrence rate of S. exigua was the highest at the basin region with 54.3%, and followed by the inland mountainous region (29.9%), the eastern middle coast region (9.3%) and the inland (3.9%), and was the lowest at the southern coast region with 2.6%. As a whole, S. litura occurred more in Gyeongnam province than Cyeongbuk province, while S. exigua occurred more in Gyeongbuk province than Gyeongnam province. According to the regions grouped by climatic differences, the occurrence of S. litura and S. exigua was the highest at the inland region in Gyeongnam province and at the basin region in Gyeongbuk province. The total number of S. litura captured by sex pheromone trap was 2.4 times higher than that of S. exigua. However, the first occurring time and the peak occurrence of S. exigua were slightly earlier than those of S. litura.

• Korean Journal of Environmental Biology
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• v.40 no.2
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• pp.187-198
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• 2022

In this study, Telenomus remus Nixon (Hymenoptera: Scelionidae) was first reported as a natural enemy of the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) egg collected from corn fields in Korea, and its biological characteristics was studied. Based on morphological and molecular analysis, the parasitoid emerged from S. frugiperda eggs was identified as T. remus. We found that T. remus can attack the eggs of S. frugiperda, Spodoptera litra and Spodoptera exigua under a laboratory condition. The longevity of T. remus female adult was longer than that of male adult. The egg-to-adult period of T. remus was not affected by the host age and sex. T. remus female adult laid at least 1-3 eggs a day to a maximum of 37 or more eggs, and the most oviposited on the 3^rd to 4^th day after emergence. The host preference for oviposition of T. remus adult was high in the order of S. litura>S. exigua>S. frugiperda. T. remus preferred to parasitize 1- and 2-day-old host egg rather than 3-day-old host egg. When compared to the sex ratio of T. remus progeny, the rate of female progeny was higher at the initiation time of oviposition, while the proportion of male progeny increased significantly with female adult age, especially after 8-day-old adult. This information may be useful for improving T. remus mass rearing system and developing a biological control program to control S. frugiperda.

• Korean journal of applied entomology
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• v.52 no.4
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• pp.295-304
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• 2013

This study aimed to understand the physiological status of the beet armyworm, Spodoptera exigua at low developmental threshold temperature (LTT) through analysis of gene-expression patterns associated with different functions (metabolism, nervous system, immune, and stress). The estimated LTTs for egg, larval, and pupal developments varied with $5.5{\sim}11.6^{\circ}C$. Larvae were able to develop at the lower temperatures than eggs and pupae. However, the physiological LTT ($15^{\circ}C$) in the fifth instar was much higher than the estimated LTT ($10.3^{\circ}C$). Gene expression patterns estimated by a quantitative RT-PCR (qRT-PCR) indicate that most genes in different functional groups increased their expressions with increase of larval instars. In the same fifth instar, as the treatment temperatures increased, the gene expression levels increased. Moreover, the newly molted fifth instar larvae were different in their gene expression rates according to their previous culturing temperatures. Most gene expressions were suppressed in the fifth instar larvae at the physiological LTT ($15^{\circ}C$). However, the larvae at $15^{\circ}C$ gradually exhibited significant increase in the gene expression rates with rearing time just like those at the higher temperature. These results suggest that S. exigua at LTT exhibits a typical gene expression pattern with maintaining significantly suppressed levels.

• Korean journal of applied entomology
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• v.55 no.2
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• pp.129-138
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• 2016

Eicosanoids are a group of C20 oxygenated polyunsaturated fatty acids (PUFAs). To monitor biosynthetic precursors of these PUFAs, this study extracted fatty acids from different tissues of the beet armyworm, Spodoptera exigua, and assessed their compositions using GC/MS. Fifth instar larvae were dissected to isolate different tissues of gut, fat body, hemocytes, and integument. From each tissue, total lipids were extracted and fractionated into neutral lipid (NL), glycolipid (GL), and phospholipid (PL). Most tissues contained palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2), and linolenic acid (18:3). However, their compositions were different among tissues and lipid types. Fat body and hemocytes possessed other type of fatty acids such as myristic acid (14:0) and three unknown fatty acids. Among lipid types, PL contained relatively high levels of linolenic acid than NL and GL, while it had lower saturated fatty acids. Total unsaturated fatty acid composition was varied among tissues and lipid types. PL was rich in unsaturated fatty acids in fat body, gut, and hemocytes. There was a significant influence of calcium-independent phospholipase $A_2$ ($iPLA_2$) on maintaining fatty acid composition because RNA interference of $iPLA_2$ expression significantly modified fatty acid compositions in NL and PL. However, this study did not detect arachidonic acid, a main eicosanoid biosynthesis precursor, in all tissues. This suggests an alternative biosynthesis of eicosanoids in insects, which is distinct from the biosynthetic pathway of mammals.

• Korean journal of applied entomology
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• v.50 no.1
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• pp.39-46
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• 2011

This study analyzed effects of different sound treatments in frequencies and intensities on digestion and immune physiological processes of the beet armyworm, Spodoptera exigua larvae. Without effect on egg hatch, sound treatments with 100-5,000 Hz at 95 dB suppressed feeding behavior and inhibited a digestive enzyme activity. In addition, two dimensional electrophoresis of midgut luminal proteins indicated a marked difference of the sound-treated larvae. In response to 5,000 Hz at 95 dB, larvae showed a significant decrease in hemocyte nodule formation against fungal challenge along with significant suppression in phospholipase $A_2$ activity in hemocyte and plasma. With increase of sound frequencies, the treated larvae showed an enhanced susceptibility to insecticides. Such sound frequency effect was significantly modulated with different sound intensities. These results suggest that sound treatment may give adverse stress to physiological processes of S. exigua larvae and may be applied to a nonchemical insect pest control.

• The Korean Journal of Pesticide Science
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• v.12 no.3
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• pp.283-290
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• 2008

Baculoviruses have been used to control some serious lepidopteran pests. However, their narrow target insect spectrum and slow efficacy are main limitations to be used in various applications. This study introduces a technique to overcome these limitations by inhibiting insect immune defence to enhance the viral pathogenicity. Polydnaviruses are an insect DNA virus group and symbiotic to some ichneumonid and braconid endoparasitoids. Cotesia plutellae bracovirus (CpBV) is a braconid polydnavirus and encodes several immunosuppressive genes. We selected seven CpBV genes and recombined them to wild type Autographa California multiple nucleopolyhedrovirus (AcNPV). A bioassay of these seven recombinants indicated that most recombinants had similar or superior efficacy to wild type AcNPV against beet armyworm, Spodoptera exigua, and diamondback moth, Plutella xylostella. Recombinant AcNPV with CpBV-ELP was the most potent in terms of lethal time by shortening more than 2 days compared to wild type AcNPV. This recombinant was further proved in its dose-dependent pathogenicity and its efficacy by spray application on S. exigua infesting cabbage cultivated in pots. We discussed the efficacy of CpBV-ELP recombinant AcNPV in terms of suppressing antiviral activity of target insects.

• The Korean Journal of Pesticide Science
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• v.20 no.2
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• pp.152-158
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• 2016

The cause of death was investigated with several dead cabbage moth larvae in breeding box. Bacterial strains were isolated and selected from the dead larvae by bioassay. One of them was identified as Serratia marcescens used by morphological characteristics and gene sequencing. S. marcescens were cultured by Luria Bertani (LB) media broth for bioassay. When 100-fold dilution of culture broth to third larvae of diamondback moth, Plutella xylostella, it was showed a 100% mortality at 2 days after treatment, and only 10-fold dilution of supernatant liquid was showed 86.6% mortality. When the culture broth of S. marcescens was applied to the larvae of beet armyworm, Spodoptera exigua, contact and feeding toxicity were 20 and 8% of mortality, respectively. Otherwise, when the culture broth of S. marcescens was applied to 5 major plant pathogens, antibacterial activities against Fusarium oxysporum, Rhizoctonia solani, Colletotrichum gloeosporioides, Phytophthora capsici and Sclerotinias clerotiorum were 4.7, 11.3, 20, 15.7 and 42.6%, respectively. Also, degradation ability of S. marcescens against protein and chitin were examined.

• The Korean Journal of Pesticide Science
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• v.15 no.2
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• pp.166-176
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• 2011

Bacillus thuringiensis CAB530 was isolated from dead Anomata albopilosa (Rutelidae: Coleoptera) and soil of green tea field, and confirmed its insecticidal activities. CAB530 isolate showed a high insecticidal activity against the beet armyworm among the many lepidopteran insects that are difficult to control. $LC_{50}$ value of CAB530 isolate against the second larva of Spodoptera exigua was $1.49{times}10^4$ spore concentration (cfu/$m{\ell}$). SDS-PAGE result of insecticidal toxin protein of CAB530 isolate showed a band at 130 kDa that is similar pattern with B. thuringiensis subsp. kurstaki that took insecticidal activity against S. exigua. Otherwise, the crystal protein of the CAB530 isolate was conformed at 65 kDa level after 30 minute of incubation in S. exigua midgut juice. Six crystal genes (cry1Aa, cry1Ab, cry1C, cry1D, cry1F and cry1I) were identified by PCR. It different from genes of B. thuringiensis subsp. kurstaki. Crystal shape and pattern of toxin protein was similar with B. thuringiensis subsp. kurstaki, however, insecticidal activity and PCR result of CAB530 isolate was similar with B. thuringiensis subsp. aizawai.

• Korean journal of applied entomology
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• v.43 no.3 s.136
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• pp.217-223
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• 2004

Polydnavirus is a symbiotic virus of some endoparasitic wasps and plays crucial roles in inhibiting immune responses and retarding development of the parasitized hosts. Cotesia plutellae bracovirus (CpBV) is a polydnavirus suggesting a major causative to change developmental physiology of the parasitized host. Here, we investigated whether CpBV can interrupt development of non-natural host. Beet armyworm, Spodoptera exigua, is used as a non-permissible host for parasitization of C. plutellae. Extract from the calyx region of C. plutellae contained CpBV, which was confirmed by immunoblotting with a polyclonal antibody raised against CpBV. One female equivalent of CpBV extract was injected into hemocoel of late 4th instar larvae of S. exigua. The injected larvae showed delayed larval period, decrease of body weight gain, and inability of pupal metamorphosis. These inhibitory effect of the CpBV extract was rescued by injection along with CpBV antibody, though the antibody itself did not give any effect on development of the larvae. This result clearly shows that CpBV can interrupt developmental physiology of a non-natural host for its symbiotic wasp.

• Korean journal of applied entomology
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• v.53 no.4
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• pp.331-338
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• 2014

Cystatins (CSTs) are reversible and competitive inhibitors of C1A cysteine proteases, corresponding to papain-like cathepsins in plants and animals. A viral CST (CpBV-CST1) was identified from a polydnavirus, Cotesia plutellae bracovirus (CpBV). Our previous study indicated that a transient expression of CpBV-CST1 interfered with immune response and development of Plutella xylostella larvae. To directly demonstrate the protein function, this study produced a recombinant CpBV-CST1 protein (rCpBV-CST1) using bacterial expression system to determine its inhibitory activity against cysteine protease and to assess its physiological alteration in insect immune and development. The open reading frame of CpBV-CST1 encodes a polypeptide of 138 amino acids (${\approx}15kDa$). rCpBV-cystatin protein in BL21 STAR (DE3) competent cells containing a recombinant pGEX4T-3:CpBV-CST1 was over-expressed by 0.5 mM IPTG for 4 h. In biological activity assay, the purified rCpBV-CST1 showed a significant inhibition against papain activity. It inhibited a cellular immune response of hemocyte nodule formation in the beet armyworm, Spodoptera exigua. Moreover, its oral administration retarded larval development of the diamondback moth, Plutella xylostella in a dose-dependent manner. These results suggest that CpBV-CST1 may be applied to control insect pest populations.