• Journal of Korean Society of Forest Science
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• v.106 no.3
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• pp.362-369
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• 2017

This study was carried out to provide basic data for active control of the anticipated damage through investigation and analysis of geographical and spatial occurrence distribution of oak wilt disease area. The damage of oak wilt disease was analyzed by investigating all the damage trees caused by oak wilt disease from 2011 to 2015 in three areas of Gwangtan-myeon, Paju-si, Gyeonggi -do. As a result, the closer to the ridge the more damage of the oak wilt was generated. Therefore, it is necessary to select the central management area from 0 to 40 m based on the ridge line for more effective control, and to intensively control the area. Also, it is difficult to predict the occurrence of damage by the slope because the damage situation represent differently by the region. By the diameter class, it was analyzed that the number of damaged trees was the largest in the average diameter class with the most number of the trees in each region.

• Microbiology and Biotechnology Letters
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• v.36 no.2
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• pp.115-120
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• 2008

Bacterial populations from the rhizosphere were obtained and the efficacy of the bacterial wilt suppression, root colonizing ability and resistance to three kinds of chemical pesticides were assayed. According to these results, SKU48-2 was selected as a potential biological agent to control the bacterial wilt caused by Ralstonia solanacearum. SKU48-2 strain at $10^8CFU/ml$ inoculum was able to suppress the bacterial wilt up to 60% in greenhouse trials. Also, the resistance of SKU48-2 to chemical pesticides make possible to use in combination with chemical pesticides for the control of bacterial wilt. Three different powder formulations of SKU48-2 were developed. The shelf-life of powder formulations was effective up to 6 months of storage. Unformulated bacterial suspension could not be stored for 2 weeks, at which time cell viability was completely lost. According to 16S rDNA sequence data, the SKU48-2 stain was identified as Bacillus subtilis.

• The Plant Pathology Journal
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• v.19 no.3
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• pp.129-132
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• 2003

Fusarium wilt of cucumber caused by Fusarium oxy-sporum f. sp. cucumerinum is a serious vascular disease worldwide. Biological control of Fusarium wilt in several crops has been accomplished by introducing non-pathogenic Fusarium sup. and other biocontrol agents in soil or in infection courts. In this study, quantitative models were used to determine the biocontrol efficacy of inundatively applied antagonist formulations and the length of their effectiveness in controlling Fusarium wilt of cucumber. Quantitative model of the form [Y=L (1${-exp}^{-kx}$)] best described the relationship between disease incidence (Y, %) and inoculum density (X) of isolates F51 and F55. Isolate F51 was selected as a more virulent isolate based on the extent of its effectiveness in causing the wilt disease. The degree of disease control (Xi/X) obtained with the density of the biocontrol agent (Z), was described by the model [Xi/X=A (1${-exp}^{-cz}$)]. The zeolite-based antagonist formulation amended with chitosan (ZAC) was better at lower rates of application and peaked at around 5 g/ kg of the potting medium, whereas the peat-based antagonist formulation (PA) peaked at around 10 g/kg of the potting medium. ZAC formulation provided significantly better suppression of Fusarium wilt as described by the curvilinear relationship of the type Y= a+bX+c$X^2$, where Y represents percent disease incidence and X represents sustaining effect of the biocontrol agent.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.240-249
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• 2006

Recently, dispersion of damaged forest by pine wilt disease has been regarded as a serious social issue. Damages by pine wilt disease have been spreaded by natural area expansion of the vectors in the damaged area, while the national wide damage spread has induced by human-involved carrying infected trees out of damaged area. In this study, damaged trees were detected and located on the digital map by aerial photograph and terrestrial surveys. The spatial distribution pattern of damaged trees, and the relationship of spatial distribution of damaged trees and some geomorphological factors were geostatistically analysed. Finally, we maked natural spread pattern map of pine wilt disease using geostatistical CART(Classification and Regression Trees) model. This study verified that geostatistical analysis and CART model are useful tools for understanding spatial distribution and natural spread pattern of pine wilt diseases.

• Journal of Microbiology and Biotechnology
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• v.30 no.5
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• pp.708-716
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• 2020

The purpose of this study was to identify strawberry wilt pathogens and evaluate the efficacy of Chlorella fusca CHK0059 for improving plant growth and suppressing Fusarium wilt. We identified 10 isolates of wilt pathogens of non-pesticide Seolhyang strawberry plant, including Fusarium oxysporum f. sp. fragariae, using morphological and molecular analysis. On the 15^th day after 0.4% CHK0059 treatment, the plant height of the untreated control strawberry plants was significantly greater than that of the CHK0059-treated strawberry plants. After 85 days, both treatments showed a similar tendency regarding the height of the strawberry plants. However, the thickness of strawberry leaves treated with the CHK0059 was found to be 1 mm thicker than that of the untreated control. The flowering percentage of the CHK0059 plants was also 40.2% higher on average than that of the untreated control. The chlorophyll content of strawberry leaves treated with the CHK0059 was also, on average, 6.63% higher than that of the untreated control. After 90 days of the CHK0059 treatment, the incidence of Fusarium wilt in the CHK0059-treated plants had reduced by 9.8% on average compared to the untreated control. The population density of F. oxysporum f. sp. fragariae was also reduced by approximately 86.8% in the CHK0059-treated plants by comparison to the untreated control at 70 days after treatment. The results indicate that the microalga C. fusca CHK0059 is an efficient biological agent for improving strawberry plant growth and suppressing Fusarium wilt disease in organic strawberries.

• Journal of Forest and Environmental Science
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• v.33 no.4
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• pp.342-347
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• 2017

Since the first report of the oak wilt disease at 2004 in Korea, the disease distributed over Korean peninsula and are still giving severe damages. The management of oak wilt disease in Korea has mainly focused on the control of insect vector, Platypus koryoensis. Neverthless the effective method for evaluating the pathogenicity of the pathogen, Raffaelea quercus-mongolicae (Rqm), and for screening chemical or biological agents with strong inhibitory activity against the pathogen, is absolutely necessary, an reliable method is not available so far. This study was conducted to develop the effective method for evaluating the pathogenicity of Rqm in oak trees. The culture suspensions of Rqm were artificially injected to the saplings of Quercus acutissima by using ChemJet tree injector. Three months after treatments, the treated saplings were cut and dipped into 1% fuchsin acid solution. There were significant differences in non-conductive area (%), discoloration area (%) and vertical discoloration length between the pathogen-injected and distilled water-injected control treatments. These results indicated that the pathogen is the causal agent for the dysfunction of water conductive tissue, which will finally result in wilt symptom. Re-isolation of the pathogen and PCR detection using specific primers for the pathogen also confirmed the presence of Rqm in the sapwood chips of the pathogen-injected saplings. These observations would be greatly applied to other related researches for evaluating the pathogenicity of tree wilt pathogens and biocontrol efficacy of the selected antagonistic microorganisms, in case that the wilt symptom is not easily shown by artificial inoculation of the causal agent.

• The Plant Pathology Journal
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• v.23 no.1
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• pp.22-25
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• 2007

Biocontrol activity of five strains of selected rhizo-bacteria were tested in tomato against bacterial wilt caused by Ralstonia solanacearum. After root bacterization the plants were grown in a perlite-hydroponic system. Upon challenge inoculation with the pathogen, all of the rhizobacterial strains efficiently suppressed the bacterial wilt in tomato in various rates, at maximum by the strain, Bacillus vallismortis strain EXTN-1. While the percent of infected plants in the non-bacterized control plants were 95%, it was only 65% in plants pre-treated with EXTN-1. It was also demonstrated that the movement of R. solanacearum within the stem was significantly hampered when the plants were root bacterized. As EXTN-1 has no antagonistic properties against R. solanacearum, the bacterial wilt was probably suppressed by a mechanism other than antibiosis. Previously, the strain had been proven to produce an efficient elicitor for inducing systemic resistance in many crops. As the present study confirmed that EXTN-1 has the ability for reducing the pathogen spread in tomato, the strain could be effectively used as a potential biocontrol agent against bacterial wilt.

• Korean Journal of Remote Sensing
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• v.35 no.3
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• pp.359-373
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• 2019

Bursaphelenchus xylophilus(Pine wilt disease) is a serious threat to the pine forest in Korea. However, dead wood observation by Pine wilt disease is based on field survey. Therefore, it is difficult to observe large-scale forests due to physical and economic problems. In this paper, high resolution images were obtained using the unmanned aerial vehicle (UAV) in the area where the pine wilt disease recurred. The damaged tree due to pine wilt disease was detected using Artificial Neural Network (ANN), Support Vector Machine (SVM) supervision classification technique. Also, the accuracy of supervised classification results was calculated. After conducting supervised classification on accessible forests, the reliability of the accuracy was verified by comparing the results of field surveys.

• Research in Plant Disease
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• v.28 no.1
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• pp.54-56
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• 2022

A peanut plant showing wilt and browned symptom was found in the field of Gochang, Korea, in July 2021. The symptomatic peanut plant was collected from the field and isolation of the pathogen caused the wilt symptom was performed using the collected sample on TZC media. The dominated colony on media was isolated colony on media was isolated and subcultured of purification. The pure cultured bacteria was identified as Ralstonia solanacearum by sequencing of 16S rRNA gene. Multiplex polymerase chain reaction using phylotype-specific primer set identified isolate as phylotype I (R. pseudosolanacearum). Phylogenetic tree was constructed based on 16S rRNA sequence and it was closed with R. pseudosolanacearum. Pathogenicity of the isolates was assessed by soil drenching inoculation on 4-week-old peanut plant. The wilt symptom was successfully reproduced by inoculation of the isolates after 14 days. This is first report of bacterial wilt caused by R. pseudosolanacearum on peanut in Korea.

• Journal of Forest and Environmental Science
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• v.34 no.5
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• pp.376-381
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• 2018

For the control of oak wilt caused by Raffaelea quercus-mongolicae, an antifungal microorganism, Streptomyces blastmyceticus, was used as a potential agent. Culture suspension of S. blastmyceticus was injected into Quercus mongolicae in the research forest of Kangwon National University by $ChemJet^{(R)}$ trunk injection and Macro-infusion at root flare injection. $Alamo^{(R)}$ (a.i., propiconazole 14.5%), a fungicide currently used for the control of oak wilt in USA, was also treated by both methods to compare the efficacy. For preventive efficacy, culture suspension of the pathogen was inoculated at 1 month after injection of either agent. Tested trees were cut at 3 months after treatment, stained with 1% Fuchsin acid, and then non-conductive area (NCA) and re-isolation frequency (RIF) of oak wilt fungus were compared among treatments. While NCA was the highest as 47.3% in pathogen only treatment, it was the lowest as 16.0% in sterilized water treatment by Macro-infusion. NCAs of Alamo treatment by Macro-infusion and ChemJet injection were 25.3% and 32.1%, respectively. NCA of S.blastmyceticus treatment by ChemJet injection was 32.3%, similar with Alamo treatment's by ChemJet injection. All treatments by either injection method showed significantly lower NCA compared to the pathogen only treatment. These results indicate that S. blastmyceticus injection shows the preventive efficacy against oak wilt disease by suppressing the growth of pathogen injected. NCA of Macro-infusion injection of sterilized water was lower as 16.0%, compared to 21.3% of ChemJet injection. It means that Macro-infusion is more effective in translocation of sterilized water than ChemJet injection by even distribution. RIF from wood discs of treated trees showed high in pathogen only treatment, but relatively low in S. blastmyceticus treatment. RIF results were correlated with NCA results. From the above results, it was confirmed that S. blastmyceticus showed preventive efficacy against oak wilt disease by ChemJet trunk or Macro-infusion at root flare injection.