• Journal of Sericultural and Entomological Science
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• v.32 no.1
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• pp.49-57
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• 1990

To investigate the pathway of Nuclear Polyhedrosis Virus(NPV) of Bombyx mori in early stage infection of 2nd instar larva, the larval tissues were observed under electron microscope at interval of 6, 12, 24, and 48 hours after virus inoculation. The results are as follows. 1. The intact and enveloped nucleocapsids released from the polyhedra protein in the gut lumen apparently entered with the microvilli. 2. Virus progenies were observed in columnar cell nuclei 24 hours after inoculation, but polyhedra was not seen. The enveloped virus was observed in some of the intercellular spaces between mid-gut cells. 3. Many enveloped virus particles appeared in the basement membrane. These enveloped virus particles passed the basement membrane and gathered at blood cells in heomocoeal. 4. The NPV muliplicates in nuclei of the blood cells and the tracheal cells normally.

• Journal of Sericultural and Entomological Science
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• v.22 no.2
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• pp.8-12
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• 1981

Practical application of silkworm artificial diet is very desirable to save labour in sericultural industry as the problem of labour shortage is becoming serious in Korea. However, silkworms reared on the artificial diet are more susceptible to viruses than those reared on mulberry leaves because of the lower anti-viral activity of gut juice of silkworms grown on artificial diet compared with that of silkworms grown on mulberry leaves. In this study, authors investigated the varietal difference of silkworm larvae, Bombyx mori L., reared on artificial diet which contained 20 percent of dried mulberry powder, in the susceptibility to nuclear polyhedrosis virus (NPV). The results showed that there is no difference in susceptibility to NPV among tested varieties when high concentration of NPV was admitted to silkworm larvae, but varietal difference appeared in lower concentration admitted. Among 7 hybrids tested, Hansaeng 1${\times}$Hansaeng 2 was most resistant to NPV with an $LC_{50}$ of 2.7${\times}$10$\^$6/ and Jam 111${\times}$Jam 112 was also more resistant comparatively than other hybrids.

• Korean journal of applied entomology
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• v.61 no.3
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• pp.449-460
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• 2022

The morphology and whole genome sequence of Spodoptera exigua nucleopolyhedrovirus K1 (SeNPV-K1) isolated in Korea were analyzed for the use as an eco-friendly control source against S. exigua. The polyhedra of SeNPV-K1 was amorphous with a size of 0.6-1.8 ㎛, and there was no external difference with the previously reported SeNPV. As a result of analyzing the nucleotide sequence of the whole genome, it was composed of 135,756 bp, which is 145 bp more than that of the previously reported SeNPV. The G+CG+C content was 44% and there were 6 homologous repeated sequences, so there was no significant difference from the previous report. As a result of ORF analysis, SeNPV-K1 had 137, two fewer than those previously reported, and 4 ORFs present only in SeNPV-K1 were confirmed. These 4 ORFs are non-essential genes and were not considered to have a significant influence on the characteristics of the SeNPV. The genome vista analysis showed that the overall sequence similarity between SeNPV-K1 and the previously reported SeNPV was very high. The whole genome of SeNPV-K1 analyzed for the first time in Korea was found to be similar to the previously reported SeNPV, but it was confirmed that it was a novel resource in Korea with different isolate.

• Korean Journal of Organic Agriculture
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• v.31 no.4
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• pp.395-412
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• 2023

The morphology and whole genome sequence of Hyphantria cunea nucleopolyhedrovirus W1 (HycuNPV-W1) isolated in Korea were analyzed for the use as an eco-friendly control agent against H. cunea. The HycuNPV-W1 had irregular tetrahedral polyhedra with a size of 1.5-2.2 ㎛ which is similar to that of previously reported HycuNPV isolated in Korea. As a result of whole viral genome analysis, HycuNPV-W1 was composed of 131,353 bp, which is 1,606 bp shorter than that of the previously reported HycuNPV. The G+C content was 45% and six of the homologous repeated regions were found, so there was no significant difference from the previous report. As a result of ORF analysis, HycuNPV-W1 contains total of 145 ORFs which is three ORFs less than the previous report, while two ORFs were exclusively found in HycuNPV-W1. The functions of these ORFs remains unclear and are not considered to have a significant influence on the characteristics of the HycuNPV. The genome vista analysis showed that the overall sequence identity between HycuNPV-W1 and the previously reported HycuNPV was very high. The whole genome of HycuNPV-W1 analyzed was found to be similar to those of the previously reported HycuNPV, however, it is supposed to be a novel resource in Korea with different isolate.

• Korean journal of applied entomology
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• v.30 no.2
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• pp.111-116
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• 1991

Larvae of beet armyworm. Spodoptera exigua are extremely polyphagous. A total of 42 host p plants were identified in the field observations. Among them, vegetables were 13 species. upland crops 12 species, flowers species, and others including weeds 11 species. The damage by b beet armyworm was severe on Allium fistulosum in southern Chonnam. The percentage of hills d damaged was 86% in Jindo, Chonnam and 1.92% in Sesan. Chungnam. Nomuraea rileyi and nuclear polyhedrosis virus were identified on the larvae of Spodoptera exigua in Allium fistulosum fields and the percentage of parasitization was 4.3-9.7% and 3.2%, respectively. M Mortality of Spodoptera exigua larvae by Nomuraea rileyi in perilla was 13.4% in July 5, 28.9% in Aug. 7, and 18.5% in Sept. 10.

• Korean journal of applied entomology
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• v.18 no.1 s.38
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• pp.1-10
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• 1979

An inclusion forming virus isolated from a fan webworm, Hyphantria cunea, in 1975 was identified as a nuclear polyhedrosis virus. With the virus isolated in Korea, it was considered that the virus would be one of the valuable microorganism in microbial control. In this connection, 1) the shape and size of the virus for identification, 2) susceptibility of the various instar larvae to the virus, 3) the effects of storage condition on the pathogenicity and the cross infection of the virus to the larvae of Bombyx mori were examined. The results are summarized as follows; 1. The polyhedron was tetrahedron or hexahedron of $2\mu$ in size and the rod-shaped virus particles consisting of $2\~14$ rods in a bundle were $330m{\mu}\times35m{\mu}$ in size. 2. The hexagonal nuclear polyhedra were found only in the nucleus of the midgut cells but were variable in size. 3. The $LD_{50}$ values for the various instar larvae of H. cunea were $8.377\times10^4\;PIBs/ml$ for the second, $4.974\times10^5\;PIBs/ml$ for the fifth instar larvae. The $LT_{50}values$ for $10^6\;PIBs/ml$ were 9.6 days for the second, 11.5 days for the third, 12.0 days for the fourth and 17 days for the fifth instar larvae. 4. The susceptibility of H. cunea to the nuclear polyhedrosis virus was greater in the first generation than in the second generation. 5. The effect of the storage conditions on the pathogenicity of the nuclear polyhedra was less in refrigerator $(5^{\circ}C)$ and in freezing $(-80^{\circ}C)$ than in room temperature $(18.5^{\circ}C)$, especially as air-dried polyhedra than as suspension. The pathogenicity of the polyhedra seemed to decrease by sunlight during storage as cadavers, since rather greater decrease in pathogenicity was found in sunny condition than in shady condition. 6. The effective spray concentration was $6.4\times10^7\;PIBs/ml$ in the field and its $LT_50$ values for the third and the fifth instar larvae were 4.8 days and 14.2 days, respectively. 7. No cross infections were found in the nuclear polyhedrosis virus between H. cunea and B. mori. larvae.