• Korean Journal Plant Pathology
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• v.3 no.3
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• pp.210-216
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• 1987

A computer program written to predict blast occurrence based on micro climatic events was developed and tested as an on-site microcomputer in field plots in 1984 and 1985. A microcomputer unit operating on alkaline batteries; continuously monitored air temperature, leaf wetness, and relative humidity; interpreted the microclimate information in relation to rice blast development and displayed daily values (0-8) of blast units of severity (BUS). Cumulative daily BUS values (CBUS) were highly correlated with blast development on the two susceptible cultivars, M-201 and Brazos grown in field plots. When CBUS values were used to predict the logit of disease proportions, the average coefficients of determination $(R^2)$ between these two factors were 71 to $91\%$, depending on cultivar and year. This was a significant improvement when compared to 61 to $79\%$ when days were used as a predictor of logit disease severity. The ability of CBUS to predict logit disease severity was slightly less with Brazos than M-201. This is significant inasmuch as Brazos showed field resistance at mid-sea­son. The results in this study indicate that the model has the potential for future use and that the model could be improved by incorporating other variables associated with host plants and pathogen races in addition to the key environmental variables.

• Research in Plant Disease
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• v.26 no.1
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• pp.29-37
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• 2020

Stem blight symptom of soybean was severely developed in 2016 in Hwaseong and Yeoncheon. During the seedling period, the damping-off of seedlings and the brown or black spots of cotyledons were observed. After August, the leaves began to be yellowed, and partially browned areas on leaves began to develop. After September, microsclerotia began to form even on the surface of the stems that had exhibited water-soaking symptom. After mid-October of the harvest season, the epidermis of the stem was peeled off, resulting in the formation of a large number of microsclerotia in the cortex. The pathogens isolated from these symptoms were the best in mycelial growth at 32-35℃, and the formation of microsclerotia was the most at 20-28℃. The pathogen was identified as Macrophomina phaseolina through the morphological characteristics of the pathogen and the sequencing of the internal transcribed spacer region gene. In addition, when inoculated with a soybean stem using toothpicks cultured with the pathogen, the same symptoms as seen on the soybean field occurred. When the pathogen was re-isolated at the lesion site, the same pathogen was isolated and identified as Macrophomina phaseolina. Based on the results, the disease is reported as soybean charcoal rot.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.387-394
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• 2013

The Rhizoctonia blight causing by Rhizoctonia spp. is an important disease of turfgrass, requiring fungicide application to maintain acceptable conditions for turfgrass good qualities in the golf course. The experiment was conducted to determine the mean 50% effective concentration inhibiting mycelial growth ($EC_{50}$) value of to flutolanil, pyraclostrobine and hexaconazole to Rhizoctonia solani AG-1 IB, Rhizoctonia cerealis and Rhizoctonia solani AG2-2IV isolated from Gyeongbuk province of Korea in vitro. Five discriminatory concentrations of each fungicide were used to detect in vitro sensitivity. The mean of $EC_{50}$ values to three systemic fungicides was the lowest isolate of R. solani AG-1 IB. However, the sensitivity of fungicides to Rhizoctonia solani AG2-2IV were higher mean $EC_{50}$ value of 0.026 ${\mu}g\;a.i.\;ml^{-1}$ of pyraclostrobine and 0.044 ${\mu}g\;a.i.\;ml^{-1}$ of flutolanil. R. cerealis was the lowest sensitivity to hexaconazole which was an average $EC_{50}$ value of 0.022 ${\mu}g\;a.i.\;ml^{-1}$. Inhibition of mycelial growth rate (%) by three combine fungicides using the $EC_{50}$ value of each fungicide was the highest R. solani AG2-2IV. Results of this study were may confirmed in vitro response fungicide of three Rhizoctonia species for control of Rhizoctonia blight in the field.

• Journal of Bio-Environment Control
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• v.21 no.2
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• pp.140-146
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• 2012

The commercial product "pyto-patch" prepared as nano sized silver particle less than 5 nm, has effective antifungal activity against Collectotrichum gloeosporioides, Botrytis cinerea, Sclerotinia sclerotiorum in vitro. As a fungal growth inhibiton mechanism, it can reduce spore germination rate and mycelial growth. As s promising fungicide, Phyto-patch can control anthracnose effectively. The spore of C. gloeosporioides dipped in 5 ppm phyto-patch dilute suppressed germination rate to 13.2%, and mycelial growth stopped for 15 days at 10 ppm. The spore postinoculated on 10 ppm phyto-path smeared PDA surface could not germinate for 3 days and prohibit pathogen infection effectively. In field test, the anthracnose development of 4 ppm phyto-patch treated plot was less than 7% after 21 days compaired to 40% of it in untreated plot. In heavy rainfall season, pepper anthracnose effectivly contrrolled by regular 10 ppm phytopatch spraying every 7 days. The diseased pepper fruit decreased to 5.8% compaired to 94.6% in untreated plot. During drying period, the diseased pepper fruit havested in phyto-patch treated plot was 24.2%, but pepper fruit havested in untreated plot destroyed to 100% within 3 days. The nano silver particle coated on multching textile prevented late blight of pepper effectively and disease occurance delayed about month.

• Research in Plant Disease
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• v.13 no.1
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• pp.40-44
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• 2007

Powdery mildew of pepper is one of the most devastating diseases which is occurring all the year under greenhouse condition. In this study, control efficacy against powdery mildew was evaluated by mixed culture solutions of two chitinolytic bacteria, Lysobacter enzymogenenes strain C-3 and Chrornobacterium sp. strain C-61, cultivated in the chitin-supplemented medium. In all experiments, white powder on the reverse side of pepper leaves perfectly disappeared 3 days after application of mixed culture solutions. However, periods required for formation of new white powder on the same sites after application (control-lasting period) were largely differed according to environmental conditions. In particular, the control-lasting period was much longer when sprayed on 6 PM than 9 AM and especially, on rainy days than sunny days. This indicates that control efficacy of culture solution may be largely affected by environmental conditions after application. The undiluted culture solution resulted in a perfect control with control value more than 95% by application of 5-day-intervals under severely diseased field and 7-day-intervals under disease-started field. A ten-fold diluted product also showed control value more than 81% by application of the same method. These results suggest that this culture solution can be practically used to control powdery mildew disease in pepper plants.

• Research in Plant Disease
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• v.14 no.1
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• pp.37-42
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• 2008

Bacillus subtilis BD0310 isolated from tea leaves was used for the development of a biofungicide against Pestitalotiopsis longiseta causing gray blight of tea plants. After mass culture of the antagonistic bacteria, the biofungicide formulated as a suspension concentrate was evaluated for its control efficacy against the gray blight of tea plant in a greenhouse and a tea plantation, respectively. Spray of the biofungicide 2 days before inoculation of P. longiseta inhibited more efficiently the development of gray blight compared with spray of the biofungicide 2 days after inoculation of the pathogen onto the leaves of tea plants in a greenhouse. In the field investigation under application of the biofungicide in 2005 and 2006, control efficiencies increased according to the number of spray of the biofungicide. Control efficiencies of the biofungicide were 52.4%, 66.7%, 71.4% and 85.7% against gray blight in 4 times spray of the biofungicide alone at 7 days interval, 6 times spray of the biofungicide alone at 7 days interval, 2 times alternate spray of biofungicide and chemical fungicide at 7 days interval and 4 times spray of chemical fungicide alone at 7 days interval, respectively. Therefore, the alternate application of the biofungicide and chemical fungicide at 7 days interval can increase the control efficiency with reduction of the amount of chemical fungicides and the number of spray for the control of gray blight of tea plants in the field.

• Research in Plant Disease
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• v.25 no.1
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• pp.38-42
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• 2019

While rehmannia (Rehmannia glutinosa Libosch) was identified as a host of at least five viruses, including Rehmannia mosaic virus (ReMV), Youcai mosaic virus (YoMV), Broad bean wilt virus 2 (BBWV2), Plantago asiatica mosaic virus (PlAMV), and Rehmannia virus 1 (ReV1), viral incidence surveys have not been performed yet in rehmannia fields in Korea. In this study, we performed field surveys during 2017-2018 to investigate the incidence of 5 major viruses in rehmannia. A total of 145 symptomatic samples were collected from the rehmannia fields in major cultivation areas of Korea. Molecular diagnosis assays showed that all the collected leaf samples were infected with more than two viruses. Particularly, two species of Tobamovirus, ReMV and YoMV, were detected in all the samples. In addition, our analysis showed that the root stocks of 4 rehmannia cultivars were infected with at least two viruses. Since rehmannia is propagated by vegetative propagation, it is highly important to produce virus-free root stocks of rehmannia to control virus diseases in rehmannia.

• The Korean Journal of Mycology
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• v.30 no.2
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• pp.152-156
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• 2002

Distribution and alteration of mating type of Korean population for Phytophthora capsici were monitored from 1995 to 1998. Total 973 isolates collected from 75 pepper fields throughout the country were divided into A1 mating type 573 isolates and A2 mating type 400 isolates. Both mating types were founded in all provinces examined, but the distribution patterns differed between the fields, The single mating type of A1 or A2 isolates was found in some fields, whereas various combinations of both mating types were in all years and provinces surveyed. Ratios of A1 and A2 were varied with years and fields. However, only single mating type either A1 or A2 was detected in some fields. While, in another field located in Gongju, only A2 isolates were detected in 1995 and 1997, but A1 isolates were appeared in 1998. Varied ratios and alterations of A1 and A2 mating type in fields indicate a potential sexual recombination of the fungus, which may cause genetic diversity.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.6
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• pp.971-976
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• 2002

Effect of storage temperature and packing method on the changes in pH, acidity, the levels of lactic acid bacteria, volume expansion of packages and the colorness during the fermentation of kakdugi (diced radish kimchi) were investigated. The fermentation characteristics were greatly influenced by the temperature. The pH of kakdugi fermented at 15$^{\circ}C$ was 4.10 at 3 days, while the pH of kakdugi fermented at $0^{\circ}C$ was 4.03 at 18 days. The acidity of kakdugi fermented at $0^{\circ}C$ very slowly increased compared to that of the kakdugi fermented at 15$^{\circ}C$, 1$0^{\circ}C$ or 5$^{\circ}C$. The required days to reach the acidity of 0.6% (optimally ripened state) were 6 days at 15$^{\circ}C$, 7 days at 1$0^{\circ}C$, 18 days at 5$^{\circ}C$ and 30 days at $0^{\circ}C$. Despite of different fermentation temperature, the numbers of Leuconostoc sp. in optimally ripened kakdugi were similar. However, Lactobacillus sp. in kakdugi fermented at $0^{\circ}C$ was the smallest in number. Also, the volume expansion of aluminum pack was the lowest in kakdugi fermented at $0^{\circ}C$. Both pH and acidity of the kakdugi fermented in different packing condition did not show any difference at 1$0^{\circ}C$ for 20 days, however, the color of the kakdugi was affected by a packing method. Aluminium laminate package in which Ca(OH)$_2$ Pack stuck inside resulted in decolorization of kakdugi compared with aluminum package without Ca(OH)$_2$ pack or plastic jar. It showed the lowest redness and the highest lightness and yellowness. These results indicated that fermentation at $0^{\circ}C$ could increase storage period of kakdugi with minimum growth of Lactobacillus sp., and plastic jar might relieve the problem of volume expansion and decolorization of kakdugi.

• Research in Plant Disease
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• v.11 no.1
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• pp.43-47
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• 2005

To investigate control efficacy of flusulfamide GR (granule) on Chinese cabbage clubroot caused by Plasmodiophora brassicae, experiment was accomplished in field located in Gangneungshi alpine area contaminated by P. brassicae. Flusulfamide GR provided control value of 84.6% and that was statistically significant difference from standard fungicides containing untreated control. To investigate ratio of reduction of resting spore according to fungicide treatment, soil of Chinese cabbage field before and after fungicide treatment were sampled and investigated density of resting spore. Resting spore density was not uniform in soil before fungicide treatment. Therefore, to investigate control efficacy of fungicide against clubroot, investigation on resting spore density was conducted before experiment and reflected in experimental design. Flusulfamide GR and DP (dust powder) provided 64.2% and 63.7% of reduction of resting spore on field soil after fungicide treatments. This result indicated that control efficacy of the fungicides was correlated with reduction of resting spore of P. brassicae. The increasing rate in fresh weight of above-ground part of Chinese cabbage by flusulfamide DP and GR, fluazinam DP and trifloxystrobin SC (suspension concentrate) was 14.3%, 13.0%, 13.8% and 3.8%, respectively. From above result, flusulmide GR have outstanding control efficacy against clubroot of Chinese cabbage and is effectively decreasing of resting spore density in soil.