• Journal of Sericultural and Entomological Science
• /
• v.34 no.2
• /
• pp.26-31
• /
• 1992

Flacherie virus (FV) and Densonucleosis virus (DNV) of the silkworm, Bombyx mori, which give the most severest damage to the silk production in korea, were fed on the mulberry wild silkworm, Bombyx mori mandarina, the mulberry pyralid, Gryphodes phyloalis, and the American fall webworm, Hypantria cunea, to investigate cross infectivity by serological and histopathological at observation. By the Ouchterlony's double difusion test the mulberry wild silkworm was infected with both FV and DNV type 1 (DNV-1) and the mulberry pyralid with DNV-1, so those were confirmed the cross infection. But the American fall webworm was not recognized the cross infection by the same method. The infection and multiplication of the FV in the mulberry wild silkworm was observed in the cytoplasm of the goblet cell with the appearance of the virus-specific vesicle. In DNV-1 infection to the mulberry wild silkworm and the mulberry pyralid, the nuclei of columnar cell in the midgut of both insects was hypertrophied and the nuclei of midgut cell of the mulberry pyralid positively stained with the feulgen stain. Multiplication of DNV-1 in the midgut cell of the mulberry wild silkworm was replicated in two different patterens as linear arrays and large masses, while that of DNV-1 in the muberry pyralid was multiplied as virus masses in several portion of the nuclei of the midgut cell.

• Korean journal of applied entomology
• /
• v.43 no.3 s.136
• /
• pp.225-231
• /
• 2004

An endoparasitoid wasp, Cotesia plutellae, has been used for a biological control agent against the diamondback moth, Plutellae xylostella. It has a symbiotic polydnavirus in their reproductive tract, which is required for its successful parasitization. Here, we measured a specific replication time of the polydnavirus during female development of C. plutellae. We, also, analyzed the reproductive potentials of female C. plutellae under mating or different host conditions. At $25^{\circ}C$, pupal C. plutellae began to develop adult tissues such as compound eyes and wings since day 2. At day 5, all adult tissues including antennae were developed and were ready to emerge. With polyclonal antibody raised against C. plutellae polydnavirus, an immunobloting could confirm virus replication at day 4 during pupal stage. Virus particles could be visualized by transmission electron microscope in the oviduct lumen of day 5 pupae. After adult eclosion, venom gland and ovarian calyx increased in size, though ovarioles did not. Mated females layed large number of eggs (over $60\%$) at first 4 days during their mean longevity of ca. 8 days at $25^{\circ}C$. Unmated females showed less active ovipositional behavior, where all the eggs developed into males. C. Plutellae parasitized both P. xylostella and fall webworm, Hyphantria cunea. However, C. Plutellae developed faster and showed higher successful paarasitization in P. xylostella than in H. cunea.

• Korean journal of applied entomology
• /
• v.45 no.3 s.144
• /
• pp.357-362
• /
• 2006

Bacillus thuringiensis strains were isolated from the domestic soil and a strain was selected that had a new host range and high toxicity against agriculture insect pest. The 142 samples of soil were sampled from the mountains, paddy fields and patches, in Daejon, Chungnam, Chungbuk and Jeonbuk and used for the investigation. Sixteen B. t strains were isolated from 12 samples among collected samples. There were 11 strains that showed toxical activity on Plutella xylostella (Lepidoptera: Yponomeutidae), 7 steins on Spodoptera litura (Lepidoptera: Noctuidae), 5 strains on Arete coerulea (Lepidoptera: Noctuidae), 5 strains on Culex pipiens pallens (Diptera: Culicidae) among the 16 isolated B. t strains. But there were not any strains that showed activity against Hyphanria cunea (Lepidoptera: Arctiidae) and Sitophilus oryzae (Coleoptera: Rhynchophoridae). And also some of B. thuringiensis strains showed insecticidal activity with 2, 3 or 4 kinds of insects. But there were also 3 strains that did not show any activities to the 6 insects which were used in the experiment. When examined with a phase-contrast microscope, the insecticidal crystal protein produced from 16 selected strains had 13 bipyramidal and 3 spherical shapes. The insecticidal bioactivity of the S. litura showed 100% mortality when there were $1.3{\times}10^{7}\;(cfu/ml)$ of CAB109 isolates.

• Applied Biological Chemistry
• /
• v.38 no.5
• /
• pp.435-439
• /
• 1995

Some characteristics and pathogenicity of Hyphantria cunea nuclear polyhedrosis virus (HcNPV), a potential microbial pesticide was studied. H. cunea NPV replicated in the nucleus of S. frugiperda cells cultured in the TNMFH medium. In case of virus infected cell, prepolyhedra formation was observed at 24hrs post-infection. At 48 hrs post-infection, Most of the infected cell contained many mature polyhedra which were released into culture media 72 hrs post-infection, with the cells grown in suspension culture, pH of the culture medium increased during the virus replication: the pH of fresh medium was 6.35 and rose to 6.77 within 120 hrs. Polyhedra formed a band in linear density gradient of sucrose by centrifugation, which co-sedimented with $50{\sim}55%$ sucrose. The shape of the purified polyhedra was mostly tetragonal hexahedron and its size was about $2.5{\mu}m$. Electron microscopy and phase contrast microscopy showed that many bundled nucleocapsids were occluded in mature polyhedra at 48 hrs post infection. H. cunea larvae infected with NPV showed a higher motality in the second and third instar than in the fourth instar. Death rate of H. cunea larvae in the second and third instar fed with leaves coated with $1.5{\times}10^{9}{\sim}l.5{\times}10^{7}PIBs/ml$ reached more than 90%.

• Journal of Sericultural and Entomological Science
• /
• v.28 no.1
• /
• pp.43-53
• /
• 1986

Among many microbial pesticides, Bacillus thuringiensis is one of the most hopeful pesticide and some commercial products have been appearing on the market. Because these commercial products contain living spores and toxins of the organism, there is a danger that living spores of B. thuringiensis may be scattered by wind and cause a great damage in the sericulture areas. In order to avoide these risks it is desirable to select the strain which has low pathogenicity to the silkworm, and at the sometime being highly pathogenic to the pest insects. Thus this study has been carried out to acquire some basic informations about the procedure of desicable strain selection. Three strains of B. thuringiensis var. kurstaki, var. dendrolimus and var. aizawai were used for the pathogenicity test on the silkworm, Bombux mori and the fall webwarm, Hyphantria cunea. Those strains were investigated by the agarose gel electrophoresis patterns of plasmid DNA determine whether mutation had occured. Pathogenicity tests were carried out of using isolated crystal proteins and spore-crystal protein to mixtures of each strain, seperatively. In case of using spore-crystal protein mixture, the order of pathogenicity in varities of B. thuringiensis against B.mopri and H.cunea were kurstaki, aizawai, dendrolimus and kurstaki, dendrolimus, aizawai, respectively. But using isolated crystal proteins, dendrolimus had the highest toxicity to H. cunea and the lowest toxicity to B. mori among tested three strains. From the above results, dendrolimus was presumed the most desirable straing for using microbial pesticide.