• International Journal of Industrial Entomology and Biomaterials
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• 제17권2호
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• pp.173-180
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• 2008

The influence of temperature and relative humidity in infection and cross-infection of Nosema bombycis and N. mylitta respectively in mulberry silkworm, Bombyx mori L. on larval mortality, multiplication of pathogens, larval weight and growth rate in three different seasons were studied. Seasons were selected in such condition, when very less fluctuations between minimum and maximum temperature and minimum and maximum relative humidity ($25{\sim}28^{\circ}C$ and $65{\sim}72%$ R.H) was observed i.e., season-1. Fluctuations between minimum and maximum temperature were less ($28.05{\sim}34.50^{\circ}C$) but R.H % was more ($55{\sim}81%$) in season-2. Fluctuations between minimum and maximum temperature and R.H % were more ($20.00{\sim}40.5^{\circ}C$ and $64.00{\sim}90.00%$) in season-3. Growth rate of microsporidian-infected silkworm is directly related to the prevailing temperature and relative humidity in silkworm. Silkworm can tolerate slight variation of temperature but slight variation of relative humidity disfavours the development of silkworm and favours the multiplication of pathogens.

• International Journal of Industrial Entomology and Biomaterials
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• 제2권2호
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• pp.129-132
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• 2001

Biometabolic assessment was made in early and late embryonic stage (just before hatching) of one poly, one bi and their hybrids (DP, YPe, DP ${\times} Ype, and YPe ${\times} DP respectively ) of Bombyx mori to observe the racial differences. Protein and nucleic acid (RNA and DNA) concentrations were recorded to be significantly higher in bivoltine breed (YPe) and also in the hybrid than the polyvoltine (DP) strain in both the stages of embryonic development. The single egg weight of polyvoltine race was lower as compared to that of bivoltine and the hybrid studied. Age specific changes in all the biomolecules were evident where protein and RNA concentrations were elevated sharply in prehatched larvae while in case of DNA it was observed to be just reverse. The differences in protein, RNA and DNA composition between breeds and hybrids reflect the racial variations in biometabolic demands responsible for differential growth and development of the breeds and hybrids.

• International Journal of Industrial Entomology and Biomaterials
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• 제3권2호
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• pp.169-175
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• 2001

A synthetic juvenoid, R394 (Ethyl 9-cyclohexyl-3, 7-dimethyl-2, 4-nonadienoate) which is known to be a strong pest control agent was administered to silkworm, Bombyx mori L. in minute quantity for improving the silk yield. Based on the result of an earlier preliminary screening, three concentrations of the compound, viz., 0.1563, 0.3125, 31.25 nl/ml were prepared in the form of an emulsion and administered topically as a single dose, to separate batches of $5^{th}$ instar silkworm at 24, 48, 72 and 96 hrs to determine the required concentration and critical time of application for an economically favourable response. Two popular commercial silkworm hybrids, PM ${\times}$ NB4D2 (multivoltine${\times}$bivoltine) and KA${\times}$NB4D2 (bivoltine$\times$bivoltine) were subjected to the experiment. The medium and absolute control were maintained in parallel to compare the results. The results showed that 0.3125 nl/ml was the best concentration of the compound and 72 hrs of $5^{th}$instar was the most favourable age for its administration to get the maximum improvement in the commercial traits. The possible role of exogenous juvenoids in eliciting favourable response in silkworm which ultimately leads to improvement in the commercial traits is discussed.

• International Journal of Industrial Entomology and Biomaterials
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• 제14권2호
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• pp.81-85
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• 2007

White Muscardine is the most common fungal disease of silkworm, Bombyx mori L. caused by the pathogenic fungus, Beauveria bassiana (Balsamo) Vuillemin. In the present investigation, an attempt has been made to screen locally available medicinal/ weed plants against Beauveria bassiana. Among the plant extracts (PE) tested, 5% aqueous crude extract of the bulb of Allium sativum (Garlic) has been found to be most effective against Beauveria bassiana. The radial growth of Beauveria bassiana in vitro was inhibited to the tune of 54.9% in aqueous extract and 54.4% in ethanolic extract of Allium sativum and correspondingly mycelial dry weight gave rise to 110.7 mg and 108.7 mg against 201.7 mg in control 15 days post treatment. Similarly, silkworm larvae topically inoculated with the Beauveria bassiana conidia ($1.8{\times}10^6/ml$) registered survival up to 53.0% against 0.0% in control after treatment with aqueous extract of Allium sativum. Simultaneously, as a preventive measure, silkworm larvae were put to rear in conidia contaminated seat paper instantly treated with aqueous extract of Allium sativum that also increased survival up to 61.0% against 4.6% in control. It is also observed that the plant extract is absolutely innocuous to silkworm.

• International Journal of Industrial Entomology and Biomaterials
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• 제1권1호
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• pp.9-17
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• 2000

Genetic variation in the domestic silkworm strains (Bombyx mori) and phylogenetic relationships between domestic silkworms and wild silkworms (B. mandarina) were investigated by using a portion of mitochondrial CGI gene sequences. Ten geographic strains of B. mori we sequenced were identical in the 410 bp-section of mitochondrial COI gene. This sequence was also identical to the homologous sequence of the four Gen-Bank-registered strains, but one strain of B. mori differed a single nucleotide (0.2%) from others. MtDNA homogeneity in the B. mori strains appears to be resulted from fixation into the mast frequent mtDNA type during the course of breeding for new strains, in which an extensive indoor rearing and removal of unwanted individuals were accompanied. In the comparisons between domestic and wild silkworms, some wild silkworms were closely related to domestic silkworms (0.2%-1.2% of divergence), but the others were not (2.7%-3.7% of sequence divergence). This result was also reflected in the phylogenetic analyses, showing two independent phylogenetic groups: one including all B. mandarina sequences and the other including both B. mandarina and B. mori sequences. Thus, domestic silkworms may have been derived from the ancestor of B. mandarina, which belongs to this group, alto-ough more extensive study will provide better understanding on this issue.

• International Journal of Industrial Entomology and Biomaterials
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• 제15권1호
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• pp.59-68
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• 2007

Changes in protein metabolism were studied in hemolymph and fat body on days 1, 3, 5 and 7 of the fifth-instar silkworm, Bombyx mori, exposed to lethal, sublethal doses and prevailing levels of fluoride in groundwater in Karnataka and Andhra Pradesh States of India. The total protein content indicated a depletion followed by a concomitant increase in accumulation of free amino acids. Concurrently, the activity of protease in both of the tissues was also increased. A steady enhancement in the activities of alanine aminotransferase and aspartate aminotransferase paralleled the elevation of glutamate dehydrogenase activity in the tissues studied. It is presumed, on the basis of these results, that the fluoride toxicity causes major changes in protein metabolism of the silkworms.

• International Journal of Industrial Entomology and Biomaterials
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• 제11권2호
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• pp.93-98
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• 2005

Studies on extended egg preservation schedule from 120 days to 180 days was taken up with 20 germplasm accessions of mutant silkworm genetic stocks of Bombyx mori L. Statistical analyses of the data collected over three trials revealed no significant changes both in the qualitative and quantitative traits of the genetic stocks between treatment (6 months egg preservation) and control (4 months egg preservation), except for fifth instar larval duration in TMS-61, TMS-62, TMS64, TMS-31 and TMS-34 shell weight in TMS-62, TMS-64 and TMS-66. Thus, the results indicate that extended schedule of 6 months egg preservation can safely be adopted, which will reduce the cost of conservation and minimize the genetic erosion owing to reduced crop cycle.

• International Journal of Industrial Entomology and Biomaterials
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• 제6권1호
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• pp.1-9
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• 2003

The silkworm, Bombyx mori, is prone to infection of various pathogenic organisms. Pebrine, one of the deadliest disease of silkworm caused by highly virulent parasitic microsporidian, Nosema bombycis has been understood since long. Infections of the disease range from chronic to highly virulent and can result in complete loss to the sericulture industry. Several strains and species of microsporidians have since been isolated from the infected silkworms; the disease is becoming increasingly more and more complex. Epizootiology, development of immunodiagnostic kit, use of chemotherapy and thermotherapy techniques has been addressed for identification and control of the disease. A technique of delayed mother moth examination, which plays a decisive role in the detection of the disease and harvestation of stable cocoon crop, has been described. An attempt has been made to review briefly the literature available on various aspects of the pebrine disease in order to develop efficient model(s) for the prevention and control of the disease and to suggest future avenues of investigation in the field of pebrine disease management.

• International Journal of Industrial Entomology and Biomaterials
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• 제6권2호
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• pp.107-113
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• 2003

Analysis of combining ability is a widely used biometrical tool to select promising parents and hybrids, to determine the kinds and relative magnitudes of genetic variability among hybrids as well as to forecast yield attributes in early breeding generations both in plants and animals. Various statistical approaches like Jinks and Hayman (1953), Griffing (1956), Kempthorne (1957) etc. have been extensively applied in plants. These approaches have also been tried in the mulberry silkworm, Bombyx mori L. In the present review, an attempt has been made to collect most of the studies carried out on combining ability in silkworm at one place and make it available to the scientists engaged in sericultural research.

• International Journal of Industrial Entomology and Biomaterials
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• 제13권2호
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• pp.119-122
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• 2006

As the Selenium is known to be growth promoter in sheep and cattle, the efficacy of selenium has been tested in silkworm Bombyx mori L. The V instar larvae were fed with lethal and sub-lethal doses of selenium treated leaves. The larvae fed with lethal dose showed a significant decrease in growth and Cocoon commercial characters. The treatment with sub lethal dose exhibited a significant increase in the growth of the silkworm. Correspondingly, the cocoon commercial characters on exposure to the lethal dose showed significant decrease and sub lethal dose showed a significant increase. In the light of similar findings reported earlier in other cocoon crops and vertebrates, it can be inferred that selenium at lower doses acts as a growth stimulator, resulting in the higher yield of cocoon crop.