• Korean journal of applied entomology
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• v.34 no.4
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• pp.314-320
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• 1995

Pathogenicity of Korean entomopathogenic nematodes against local insect pests was different depending on strains or target-insect pests. Mortalities of diamondback moth, Plutella xylostella larvae were 51.8%, 77.8%, 96.3% or 100% in Hanrim Steinernema sp. and 50.0%, 74.1%, 96.3% or 98.1% in Hamyang Heterorhabditis sp. on filter paper when larvae were exposed to 3, 6, 12, or 24 nematodes per larva. Mortalities of them on kale leaves at the same concentration were 44.4%, 63.0%, 76.1%, or 94.5% in Hanrim Steinernema sp. and 79.7%, 81.6%, 94.4%, or 100% in Hamyang Heterorhabditis sp., respectively. In field test, control value of Hanrim Steinernema sp. was 72.0% and that of Hamyang Heterorhabditis sp. was 84.1% in 14 days when 300,000 nematodes were sprayed to each plot ($13.27\m^2$). Although mortalities of rice stem borer, Chilo suppressalis larvae showed no difference at high concentration, Hamyang Heterorhabditis sp. (47.3~100%) was more effective than Hanrim Steinernema sp. (34.3~83.3%) at low concentration, 50~200 nematodes/ml. When chestnut curculio, Curculio sikkimensis larvae were treated with Sancheong Steinernema sp. and Hamyang Heterorhabditis sp., respectively. When pellucid zygaenid, Pryeria sinica larvae were exposed to nematodes, Pocheon Steinernema sp. was effective ranging from 96.7% to 100% but mortalities of them were 63.3~76.7% in Dongrae Steinernema sp..

• Korean journal of applied entomology
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• v.48 no.1
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• pp.21-27
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• 2009

Paromius exiguus (Distant) has caused serious damage by pecky grains around Gimpo paddy fields in 2001. We conducted field and laboratory studies to determine the seasonal occurrence and age distribution of P. exiguus on the three major host plants. The overwintering P. exiguus was found mainly on the basal part of gramineae weeds in various localities. After overwintering, in mid-May, the adults aggregated on the grain parts of Imperata cylindrica, laid their eggs and nymphs developed into adults on the same host plants. By the time, the Calamagrostis epigeios colony had newly occupied I. cylindrica areas, the nymphs and adults of first generation had already moved to the second host. The second generation of P. exiguus, after having completed its life cycle on C. epigeios, the newly emerged adults migrated to the rice plants and other gramineae weeds in early August. Afterwards, they complete its third generation cycle where they can move to the overwintering site again. P. exiguus has the five nymphal stages and each nymphal stage could be determined by head or prothoracic width. On the I. cylindrica and O. sativa hosts, the age distribution of P. exiguus showed a simple structure as each stage ratio increased stepwise with time. But in case of C. epigeios, as the newly emerged adults and immature nymphs continuously migrate after a month from the I. cylindrica, the age structure became remarkably complex. The peak nymphal density was observed when the ratio of third and forth instar was the highest in the population. The finding about the specific age structure on each generation of the insect would be very useful in control decision making on the major host plants. It is also important to consider the host's specificity to pesticide sensitivity in relation to various nymphal stages.

• Research in Plant Disease
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• v.13 no.3
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• pp.131-136
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• 2007

Occurrence of popcorn disease on mulberry fruits was surveyed in several locations in Korea from 2005 to 2007. The diseased fruits turned grayish white and changed to hard and black sclerotia during overwintering after falling onto the ground. Apothecia produced from overwintered sclerotia in the fields of mulberry trees were observed in early May. Two types of apothecia were produced from the sclerotia, which were cup-shaped or club-shaped. The fungus with cup-shaped apothecia was identified as Ciboria shiraiana, and that with club-shaped apothecia as Scleromitrula shiraiana. C. shiraiana occurred at the ratio of about 6 vs. 4 in the fields. Occurrence of the disease differed remarkably depending on years, locations, and varieties of mulberry trees investigated. Field survey of the disease incidence showed that Baekhahyeongsang, Dahojosaeng, Hasusang, a native variety and Sawonppong 22 were resistant to the disease, Cheongilppong, Daeseongppong, Guksang 20 and Turkey-D were moderately susceptible, and Cateneo, Moreji and Sanggwa were highly susceptible. Disease incidence in the fields mulched with nonwoven fabrics or plastic films was much lower than that in the non-mulched fields. Disease incidence in the fields mulched with rice straws was similar to that in the non-mulched fields.

• Korean Journal of Agricultural Science
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• v.11 no.2
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• pp.278-283
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• 1984

Shearing characteristics of cornstalks were investigated under quasi-static conditions at various knife approach angles and shear angles in order to determine their importance to the cutting action of mowers. Corn variety used in this study was pioneer that was grown in the field of Chungnam National University. The results obtained were as follows: 1. The shearing process had two shearing stages in cornstalks, which was different from those of rice and other forage crops due to the hard crust. 2. Force and energy of shear were decreased progresively with height of the cornstalks. 3. The minimum shear force occured at shear angle of about $60^{\circ}$ and approach angle of about $10^{\circ}$ 4. The condition of minimum shear energy coincides with that of minimum shear force. 5. Effects of knife approach angles were more significant than those of shear angle for force and energy of shear.

• Korean journal of applied entomology
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• v.35 no.1
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• pp.52-57
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• 1996

This experiment was carried out to evaluate the effect of sublethal doses of BPMC, etofenprox,and buprofezin on N. lugens. and its predator C. lividipennis. Buprofezin was found to be the most toxic to N. lugens and the most safe to C. lividipennis among the three insecticides, based on LD50 values. Selective toxicity index calculated by dividing LDSo value of C. lividipennis by that of N. lugens indicated that buprofezin was very safe to C. lividipennis, showing selective toxicity of 2703.3. Longevity and fecundity of N. lugens treated with LDIU and LDm of buprofezin and BPMC were not significantly different with those of untreated brown planthoppers. However, egg hatchability' of N. lugens was greatly reduced when treated with LDm of buprofezin, having the highest inhibition rate of 17.7%. Hatchability of eggs from insects treated with BPMC was similar to that of control. The oviposited peak of treated hoppers appeared late as compared to the untreated which showed the peak at early part of the ovipositional period. The longevity and fecundity of C. lividipennis treated with BPMC were significantly reduced as compared with the untreated. Etofenprox also induced fecundity reduction when treated with LDlo, and LDm. However, C. lividipennis treated with sublethal doses of buprofezin showed no redution in logevity and fecundity. From these results, it may be said that buprofezin can be used to control brown planthopper without disrupting of C. lividipennis population in the rice field.

• Korean journal of applied entomology
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• v.35 no.1
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• pp.58-65
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• 1996

This experiment was carried out to evaluate the effect of sublethal doses of BPMC, etofenprox, and buprofezin on N. lugens. and its predator C. lividipennis. Buprofezin was found to be the most toxic to N. lugens and the most safe to C. lividipennis among the three insecticides, based on LD50 values. Selective toxicity index calculated by dividing LDSo value of C. lividipennis by that of N. lugens indicated that buprofezin was very safe to C. lividipennis, showing selective toxicity of 2703.3. Longevity and fecundity of N. lugens treated with LDIU and LDm of buprofezin and BPMC were not significantly different with those of untreated brown planthoppers. However, egg hatchability' of N. lugens was greatly reduced when treated with LDm of buprofezin, having the highest inhibition rate of 17.7%. Hatchability of eggs from insects treated with BPMC was similar to that of control. The oviposited peak of treated hoppers appeared late as compared to the untreated which showed the peak at early part of the ovipositional period. The longevity and fecundity of C. lividipennis treated with BPMC were significantly reduced as compared with the untreated. Etofenprox also induced fecundity reduction when treated with LDlo, and LDm. However, C. lividipennis treated with sublethal doses of buprofezin showed no redution in logevity and fecundity. From these results, it may be said that buprofezin can be used to control brown planthopper without disrupting of C. lividipennis population in the rice field.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.3
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• pp.318-325
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• 1986

The studies were performed to obtain the basic informations on the influence of weather condition for grain yield and yield components in barley. The data of Olbori tested in 9 sites for 12 years were used in the studies. Milled grain yield was decreased in paddy field after rice harvested comparing to the upland condition, and yield potential was differed by test sites with the most stable yield in Gyeongnam. The coefficients of variation analyzed for milled grain yield by years were 12.2-42.6% with the differences between high-yield and low-yield year. Heading date was earlier in high-yield year and southern part compared to the low-yield year and middle part of the Korean peninsular showing the negative correlation between grain yield and heading date. High-yield year showed longer in culm length, shorter in spike length, almost same in number of grains per spike, and lower in 1,000grain weight compared to the low-yield year. Correlation analyzed between number of spikes and grain yield showed positive relationship. Temperatures affected to the grain yield analyzed by high in vegitative growth stage, low in alternative growth stage, and almost same in reproductive growth stage in high-yield year comparing to the low-yield year, however no remarkable differences of temperatures affected were detected in over wintering stage between high-yield and low-yield year. Precipitation amount in high-yield year was lesser in sowing time, more in seedling time, and lesser in over wintering time than those of the low-yield year. Correlation between rainfall amount in the early of April and grain yield showed significant negative correlation with the remarkable affects to the grain yield. Sunshine hours in high-yield year were longer in sowing time, shorter in over wintering time, and after the over wintering time to harvesting time was longer than those of the low-yie-ld year.

• Korean Journal of Environmental Agriculture
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• v.23 no.3
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• pp.133-137
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• 2004

Recently, saw dust manure has been widely used in horticultural crop production in Korea. Animal manure is produced by decaying of livestock manure mixed with saw dust, and contained higher nutrients and ion concentration than the traditional manure made from rice straw and grasses. Therefore, a continuous application of the animal manure disregarding to soil characteristics may be ruined the soil conditions. This study was conducted to investigate the transportation of the nitrogen, phosphate, potassium, and ion concentration of the animal manure applied to volcanic and non-volcanic soils in Jeju islana Soil chemical analysis were done before and 180 days after animal manure application. After animal manure application, $NO_3$-N moved up to 90cm in volcanic soil, while the movement was limited to 60 cm in non-volcanic soil. Phosphate concentration was high up to 30 cm, where crop roots are mainly distributed, in volcanic soil, however, the phosphate moved up to 60 cm in volcanic soil. Exchangeable potassium moved up to 90 cm in volcanic soil, but the movement wns limited up to 60 cm in non-volcanic soil. For both soil types, no significant different in ion concentrations was observed up to 60 cm in soil depth, though the concentrations were higher in volcanic ash soils as compared to the non-volcanic ash soils.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.1
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• pp.70-76
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• 1992

A field experiment was conducted to find out the influence of cropping systems under rotation of paddy-upland soil on soil microorganisms with specific reference to cations concentration in the soil. The results obtained was summarized as follows. 1. The number of soil bacteria and actinomycetes increased in fallow, continuous cultivation of rice and soybean while the number of fungi decreased. 2. Gram negative bacteria as Pseudomonas spp. and Rhizobium spp. remarkably incerased with increasing Gram positive bacteria of Bacillus subtilis in continuous cultivatio of soybean. 3. The relative population of soil born plant pathogen such as Fusarium spp. Rhizoctionia spp. and Phoma spp. to the total soil fungi was high in cultivation of potato and Chinese cabbage. The ratio of soil plant pathogen to the total soil fungi was high in cultivation of potato with Chinese cabbage. 4. The number of bacteria and actinomycetes was positively correlated with ratio of Ca＋Mg/K in soil while negatively correlated with soil fungi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1196-1203
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• 2012

This paper presents a study on the calibration of a C-band HPS(Hongik Polarimetric Scatterometer) system using the DMMCT(Differential Mueller Matrix Calibration Technique). For calibration of the polarimetric scatterometer system, a fully-polarimetric antenna pattern(magnitudes and phase-differences) of the antenna main-beam is measured using a conducting sphere at anechoic chamber. The polarimetric scatterometer system could be accurately calibrated after retrieving its distortions using the DMMCT. Unlike a single-polarimetric system, in a fully-polarimetric system, not only backscattering coefficients but also phase differences are important parameters. This calibrated HPS system can be used to measure accurate Mueller matrices of bare soil surfaces, rice paddies, and vegetation fields. The phase-difference parameters as well as the backscattering coefficients for co- and cross-polarizations can then be obtained. The accuracy of calibration was verified by comparing the measured backscattering coefficients with a scattering model. The measured polarization response of a plowed bare field was also compared with the polarization response which was synthesized using a polarimetric scattering model for verifying the calibration technique.