• Korean Journal of Organic Agriculture
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• v.6 no.1
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• pp.133-149
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• 1997

Recently, the importance of management and cultivation of grasses has been increased in Korea. Among these cultural practices, the appropriate control of diseases is considered more important than other cultivation techniques such as fertilization and irrigation. The damages of brown patch and large patch caused by Rhizoctonia spp. and Pythium blight caused by Pythium spp. are serious in the major cultivation area of turfgrass in Korea. Since these diseases are difficult to control by agrochemicals, the damages are very serious if these are occured. The periodic spray of agrochemicals, to protect and control these diseases could make some problems of toxicity and environmental pollution as well as rising of non-target diseases. Therefore, the biological methods to control diseases have been required to decrease problems resulted from overuse of agrochemicals, to conserve natural ecosystem, and to control effectively diseases of grasses in the long period. The number of studies about biological control using antagonistic microorganisms have been increased for last half century. However, the application of biological control method has been very limited. In this study, thirteen isolates of R. cerealis, 8 isolates of R. solani and 3 isolates of Phthyn spp. have been isolated from diseased turfgrass in golf course and grass-culture area that have patch and wilting symptoms of zoysia grass and creeping bentgrass. Isolation frequency of R. cerealis and R. solani was high in especially zoysiagrass, while Pythym spp. was isolated from bent grass at low frequency but showed high pathogenicity. Totally, 205 isolates of soil microorganisms were isolated in this study as primary antagonistic microorganism by Herr's triple agar layer plate and dual culture method using rhizosphere of grasses, soil of crop field as the source of antagonistic microorganisms. Among the 205 isolates, 23 isolates were actinomycetes and 182 isolates were bacteria. All of the actinomycetes were isolated by Herr's method. Antagonistic effect of primary isolated microorganisms was tested for in vitro mycelial growth inhibition against pathogenic fungi isolated from grasses and for inhibition of disease occurrence in 24 well tissue culture plate and pot experiment. Then, four isolated of bacteria which are BG23, BG74, BG136 and BG171 were selected as antagonistic microorganisms against soil-born pathogenic fungi of bentgrass.

• Research in Plant Disease
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• v.7 no.3
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• pp.134-139
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• 2001

Effects of tomato-juice and KH$_2$PO$_4$ as exogenous nutrients on the infection of Botrytis cinerea LVF12 and pathogenicity to tomato were investigated. B. cinerea LVF12, which was previously reported as a casual agent of the gray mold rot of perilla, was used for pathogenesis on tomato leaves. No infection was induced, and no lesion developed on tomato leaves by the conidial suspension of LVF12 when the inoculum was prepared in sterilized water. However, when the conidial suspensions of LVF12 added with various concentrations and conditions of tomato-juice were inoculated on whole tomato plants, the disease was induced readily, Among them, 20% tomato juice with 0.1M KH$_2$PO$_4$ appeared to be the most suitable nutrient to promote high disease incidence on tomato. For the pathogenicity test according to the growing stage of tomato, the mature leaves were more susceptible than seedlings. Symptoms on the infected plants were initial small gray spots at the inoculated area. Later the whole leaves, petioles and stems became gray and eventually fell off, Under high humidity conditions, the diseased leaves and stems were covered with gray hyphae and conidia. All symptoms of infected plants were identical to those in the field conditions.

• Korean Journal of Veterinary Service
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• v.34 no.1
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• pp.37-43
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• 2011

This study was conducted to investigate the prevalence and genotypes of extended-spectrum ${\beta}$-lactamase (ESBL) in 377 Escherichia coli isolated from healthy and sick animals. Two isolates (0.5%), each of which were isolated from diseased swine and chicken, respectively, were confirmed as ESBL producing isolates by double disk synergy test, and showed a multidrug resistant phenotype. Minimum inhibitory concentration of cefotaxime for the two ESBL producing isolates were 3~4 times higher than those of ceftazidime, respectively. By PCR and sequencing, one isolate from swine have both $bla_{CTX-15}$ and $bla_{TEM-1}$, and one isolate from chicken have $bla_{CTX-15}$ and $bla_{TEM-116}$. Also, these genes were transferred to E. coli J53 by conjugation. These two isolates showed unrelated pulsed-field gel electrophoresis. To our knowledge, this is the first time that $bla_{TEM-116}$ gene was identified in E. coli isolated from animals in Korea. These results suggest more prudent use of third- generation cephalosporins, and surveillance and monitoring for ESBL producing E. coli in both animals and their environments should be necessary.

• Korean Journal of Organic Agriculture
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• v.21 no.2
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• pp.265-270
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• 2013

Cooking oil and yolk mixture (COY) was applied to control the powdery mildew of sweet persimmon at the research field of Gyeongsangnam-do Agricultural Research and Extension Services from 2010 to 2011. COY was sprayed three times with 10 days interval on foliar parts of sweet persimmon and the disease development was monitored after 5 days of final spray. Diseased leaf area rate was 13.4% and the control efficacy of COY against powdery mildew was 80.5%. Disease rate was 68.6% on negative control. Using scanning electron microscope (SEM), the morphological changes of the powdery mildew fungus on the leaf surface were observed. On COY-treated leaves, fungal mycellia were morphologically characterized by a loss in cell volume, shriveling, plasma membrane rupture, and subsequent loss of intracellular contents. It may due to the destruction of fungal cell wall or membrane structure.

• Journal of fish pathology
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• v.9 no.2
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• pp.137-145
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• 1996

A specific disease syndrome, which led to massive mortality on larve of rockfish(Sebastes schlegeli) in marine hatcheries at Chungnam area during the period 1995~1996 was studied. The causative agent isolated from the diseased or dead larvae was identified as Vibrio ordalii on the basis of biochemical and biological characteristics. In the experimental challenges aganist 0 and 1 summer fish conducted at two different temperatures as $18^{\circ}C$ and $25^{\circ}C$, Vibrio ordalii showed higher virulence to no summer fish at $18^{\circ}C$ than 1-summer fish at $25^{\circ}C$. These results were consistent to field data obtained during epizootic outbreaks in the farms. Moribund and died larvae presented telangiectasis of secondary gill lamella and brain, dissecting of respiratory epithelium, atrophy of hepatic cells and necrosis of kidney associated with the presence of the bacteria. But the digestive tissue of these fish showed no significant change.

• The Plant Pathology Journal
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• v.31 no.4
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• pp.371-378
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• 2015

Surveys of yellowing viruses in plastic tunnels and in open field crops of melon (Cucumis melo cultivar catalupo), oriental melon (C. melo cultivar oriental melon), and cucumber (C. sativus) were carried out in two melon-growing areas in 2014, Korea. Severe yellowing symptoms on older leaves of melon and chlorotic spots on younger leaves of melon were observed in the plastic tunnels. The symptoms were widespread and included initial chlorotic lesions followed by yellowing of whole leaves and thickening of older leaves. RT-PCR analysis using total RNA extracted from diseased leaves did not show any synthesized products for four cucurbit-infecting viruses; Beet pseudo-yellows virus, Cucumber mosaic virus, Cucurbit yellows stunting disorder virus, and Melon necrotic spot virus. Virus identification using RT-PCR showed Cucurbit aphid-borne yellows Virus (CABYV) was largely distributed in melon, oriental melon and cucumber. This result was verified by aphid (Aphis gossypii) transmission of CABYV. The complete coat protein (CP) gene amplified from melon was cloned and sequenced. The CP gene nucleotide and the deduced amino acid sequence comparisons as well as phylogenetic tree analysis of CABYV CPs showed that the CABYV isolates were undivided into subgroups. Although the low incidence of CABYV in infections to cucurbit crops in this survey, CABYV may become an important treat for cucurbit crops in many different regions in Korea, suggesting that CABYV should be taken into account in disease control of cucurbit crops in Korea.

• Korean Journal of Agricultural Science
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• v.49 no.1
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• pp.113-120
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• 2022

Leaf blight disease caused by Stemphylium species is an important disease in Allium crops, specifically onion, garlic and welsh onion. In 2018, leaf blight symptoms were severe and damaged onion and garlic in Jeonnam province in Korea. In addition, small purple spots on garlic burbs were observed in a post-harvest storage warehouse. Several Stemphylium isolates were isolated from diseased leaves from the field and from garlic bulb samples and were analyzed in terms of homology and the phylogenetic relationship based on the internal transcribed spacer region and calmodulin gene sequence. The results showed that among three Stemphylium species identified, S. vesicarium is most prevalent on onion and garlic. S. eturmiunum was for the first time identified as pathogenic to onion and garlic, whereas S. solani was found in welsh onion crops. Although these isolates grew well at the optimum temperature at 20 - 25℃, they could also grow at low temperatures of 10 - 15℃. A pathogenicity test was conducted using S. vesicarium and S. eturmiunum on onion and garlic respectively. These results showed that two Stemphylium species were highly virulent with cross pathogenicity in onion and garlic. The results of this study can support the biological characterization of Stemphylium species in Korea. Moreover, further research will need to develop fungicide application strategies for onion and garlic crops.

• Research in Plant Disease
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• v.14 no.1
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• pp.21-25
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• 2008

This study was conducted to decide disease incidence level of rice leaf blast required for reasonable fungicide application in paddy field. We induced the disease development by inoculating rice blast pathogens on rice seedlings (Jinmibyeo) in the greenhouse and transplanting the infected seedlings in the field two weeks after rice plants were transplanted. We scored the disease incidence, grouped and marked according to degree of percentage of diseased leaf area at maximum stage of disease development. The percent diseased leaf area (PDLA) had negative correlations with panicle number per hill, ripened grain (%), and total yield; their correlation coefficients (r), $-0.97^{**}$, $-1.00^{**}$ and $-0.96^{**}$, respectively. However, it had positive correlations with spikelets per panicle and thousand grain weight; their correlation coefficients (r), $0.98^{**}$ and $0.98^{**}$, respectively. Gain threshold (GT) calculated based on control cost and market price was estimated to be 8.35. Economic injury level (EIL) obtained based on GT and coefficient of damage of regression equation between disease incidence and the different yield components; panicle number per hill, spikelets per panical, ripened grain(%), thousand grain weight and yield were 41.8, 9.7, 19.1, 291.1 and 3.4%, respectively. Economic threshold (ET) for yield was 2.7% ($3.4%(EIL){\times}0.8$) on PDLA. These results suggest that application of fungicide is necessary when two under leaves are almost covered with lesions or contained more than twenty large lesions under leaves at maximum tillering stage.

• 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.

• Korean journal of applied entomology
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• v.21 no.2 s.51
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• pp.61-67
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• 1982

The strawberry cultivar Hokowase showing rapid wilting and death around harvest time was first found in the fold at Woongcheon, Chungnam province in 1974. The fungus, Fusarium oxysporum was isolated frequently from the crown, petiole and root of strawberry plants collected from Woongcheon and was pathogenic to Hokowase. The fungus abundantly produced micro-and macro-conidia and chiamydospore on PSA. The size of micro conidia, macro conidia and Chlamydospores was $5.0\~13.0\times2.5\~3.0,\;12.8\~62.5\times2.5\times50\mu\;and\;7.5\~13.8\times5.5\~12.5\mu$, respectively. Mycelial growth of the fungus was best between $25\~30^{\circ}C$ on PSA. The disease at Woongcheon occurred from the end of March and incidence of the disease increased from the beginning of May reaching $40.2\%$ of diseased Plants at the 1st part of June. In laboratory and field evaluation tests with twelve fungicides, Difolatan, Benlate T and Tospin M showed some control effects against the disease although they did not show ignificant differences in effects compared with that of the non-treatment. The cultivar Yachiyo, Daehak 1, Line 10-2, and Senga Sengana were highly resistant, and Harunoka and Empire were moderate resistant whereas Northwest and Hokowase were highly susceptible to the fungus under field condition.