• The Plant Pathology Journal
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• v.36 no.6
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• pp.579-590
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• 2020

Botrytis cinerea, which causes gray mold disease in more than 200 plant species, is an economically important pathogen that is mainly controlled by synthetic fungicides. Synergistic fungicide mixtures can help reduce fungicide residues in the environment and mitigate the development of fungicide-resistant strains. In this study, we screened microbial culture extracts on Botrytis cinerea to identify an antifungal synergist for tebuconazole. Among the 4,006 microbial extracts screened in this study, the culture extract from Schizophyllum commune displayed the most enhanced activity with a sub-lethal dosage of tebuconazole, and the active ingredient was identified as schizostatin. In combination with 5 ㎍/ml tebuconazole, schizostatin (1 ㎍/ml) showed disease control efficacy against gray mold on tomato leaf similar to that achieved with 20 ㎍/ml tebuconazole treatment alone. Interestingly, schizostatin showed demethylation inhibitor (DMI)-specific synergistic interactions in the crossed-paper strip assay using commercial fungicides. In a checkerboard assay with schizostatin and DMIs, the fractional inhibitory concentration values were 0.0938-0.375. To assess the molecular mechanisms underlying this synergism, the transcription levels of the ergosterol biosynthetic genes were observed in response to DMIs, schizostatin, and their mixtures. Treatment with DMIs increased the erg11 (the target gene of DMI fungicides) expression level 15.4-56.6-fold. However, treatment with a mixture of schizostatin and DMIs evidently reverted erg11 transcription levels to the pre-DMI treatment levels. These results show the potential of schizostatin as a natural antifungal synergist that can reduce the dose of DMIs applied in the field without compromising the disease control efficacy of the fungicides.

• Applied Biological Chemistry
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• v.46 no.4
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• pp.280-284
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• 2003

To develope of diagnosis and estimation system for utility of fungicides and insecticides as crop protection agents, various 10 physicochemical parameters, hydrophobicity (LogP), dipole moment (DM), HOMO energy, LUMO energy, molar refractivity $(MR:\;cm^3/mol)$, polarizability $(Pol:\;A^3)$, van der Waals molecular surface area $(A^2)$, van der Waals molecular volume $(Vol:\;cm^3)$, molecular weight (amu), hydration energy (Kcal/mol) for the active ingredients of 133 fungicides and 152 insecticides were calculated. And then the distribution ranges for each of the physicochemical parameters in fungicides, sterol biosynthesis inhibitors (DMI: demethylation inhibitor), insecticides and acetylcholine esterase inhibitors (AChE) were confirmed. It is suggested that the various compounds based on the range of the physicochemical parametes could be predicted for possibilities as fungicides and insecticides.

• Korean Journal of Agricultural Science
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• v.44 no.3
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• pp.339-347
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• 2017

Sclerotium rolfsii causing southern blight on numerous vegetable and fruit crops was isolated from stems of chili peppers showing wilting symptoms. The pathogen was identified by morphological observation and DNA sequencing analysis of ITS region. To select an effective fungicide for control of southern blight, we investigated the inhibition efficacy of thirty fungicides included in nine groups of fungicides with different mechanisms of action. A fungal growth inhibition assay was conducted through an agar dilution method by using mycelial discs and sclerotia of the pathogen as inoculum, respectively. When mycelial discs were used as an inoculum, several fungicides showed good inhibitory activity against the mycelial growth of S. rolfsii 12-6. All DMI fungicides tested had a good inhibition except for prochloraz which had low inhibitory effect. All strobilurin fungicides tested except for kresoxim-methyl and all SDHI fungicides tested except for boscalid and fluopyram, had a good inhibition. Also, fludioxonil, a protective fungicide and fluazinam had a good inhibitory effect. Interestingly, when sclerotia were used as an inoculum, inhibition efficacy was increased for fluopyram, a SDHI fungicide, and for some protective fungicides such as propineb, chlorothalonil, dithianon, and folpet. All the fungicides selected in this study should be tested in the field for their control activities against stem rot for practical use in chili pepper cultivation.

• Korean Journal of Environmental Agriculture
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• v.25 no.1
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• pp.85-92
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• 2006

Fungicides including keroxym-methyl (strobilurin fungicide), fenarimol and trifulmizole (DMI, boscalid (anilide) and metrafenone (benzophenone) were evaluated for preventive and curative efficacies against powdery mildew on oriental melon. The fungicides were applied preventatively at 7 days, 3 days and 3 hours before inoculation. Curative applications were made by applying fungicides three times at the interval of one week when infected leaves by powdery mildew were about 16% or 30%. Then preventative and curative efficacies were evaluated one week after inoculation and final application, respectively. Boscalid and metrafenone showed preventive efficacies of 74.3 and 68.3% against powdery mildew development respectively, when treated at 7 days before inoculation. They showed 89.4 and 87.2% efficacies when treated at 3 days before iniculation and 98.5 and 93.2% at 3 hours before inoculation respectively. However, there were no preventive efficacies in kresoxym-methyl, triflumizole and femarimol (DMI fungicides) when trebled at both 7 and 3 days before inoculation. At the preventive treatment 3 hours before inoculation, they indicated 59.0, 42.5, and 37.2% efficacies, respectively. When leaves were infected about 30% by powdery mildew, curative application of boscalid and metrafenone showed 85.9 and 74.0% of efficacies, respectively. Curative efficacies of kresoxym-methyl, tiflumizole and fernarimol were 5.5, 23.0 and 46.7% respectively. When leaves were infected about 16%, curative application of boscalid and metrafenone showed 100 and 97.5% of efficacies, respectively. However, the triflumizole and fernarimol showed relatively low curative efficacies of 30.8 and 51.6%, respectively. Microscopic observation of mycelial growth and conidia formation after detection of powdery mildew disease indicated lysis of mycelium and these lysis suppression of conidia formation showed tendency in accordance with curative efficacies of fungicides.

• The Plant Pathology Journal
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• v.30 no.4
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• pp.397-406
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• 2014

Maize is a socioeconomically important crop in many countries. Recently, a high incidence of stalk rot disease has been reported in several maize fields in Gangwon province. In this report, we show that maize stalk rot is associated with the fungal pathogens Fusarium subglutinans and F. temperatum. Since no fungicides are available to control these pathogens on maize plants, we selected six fungicides (tebuconazole, difenoconazole, fluquinconazole, azoxystrobin, prochloraz and kresoxim-methyl) and examined their effectiveness against the two pathogens. The in vitro antifungal effects of the six fungicides on mycelial growth and colony formation were investigated. Based on the inhibition of mycelial growth, the most toxic fungicide was tebuconazole with 50% effective concentrations ($EC_{50}$) of < $0.1{\mu}g/ml$ and $EC_{90}$ values of $0.9{\mu}g/ml$ for both pathogens, while the least toxic fungicide was azoxystrobin with $EC_{50}$ values of 0.7 and $0.5{\mu}g/ml$ for F. subglutinans and F. temperatum, respectively, and $EC_{90}$ values of > $3,000{\mu}g/ml$ for both pathogens. Based on the inhibition of colony formation by the two pathogens, kresoxim-methyl was the most toxic fungicide with complete inhibition of colony formation at concentrations of 0.1 and $0.01{\mu}g/ml$ for F. subglutinans and F. temperatum, respectively, whereas azoxystrobin was the least toxic fungicide with complete inhibition of colony formation at concentrations > $3,000{\mu}g/ml$ for both pathogens.

• Research in Plant Disease
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• v.14 no.2
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• pp.95-101
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• 2008

Fungicide resistance of cucumber powdery mildew was screened among the pathogens isolated from diseased plants in main cucumber productuion areas in Gyeonggi Province. Each fungicide from different activity group for the control of powdery mildew were sprayed on cucumber leaves according to application concentration. Each conidia mixed with sterilized water isolated of pathogens were transferred on the cucumber leaf disks treated with each fungicide. At 7 to 9 days after inoculation of pathogen, disease severity was recorded under the microscope. Most of pathogen isolates showed moderate resistance to difenoconazole belonged to DMI group fungicide while some isolates from Osan were resistant even $300{\mu}g/ml$. Isolates from Pyeongtaek, Osan and Yongin area also showed moderate resistance to fenarimol while one isolate showed resistant to fenarimol even $300{\mu}g/ml$. Most of isolates from Pyeongtaek, Osan and Yongin showed highly resistant to azoxystrobin belonged to strobilurin group fungicide. Standard sensitive isolates the minimum inhibition concentration(MIC) value for azoxystrobin showed $200{\mu}g/ml$ while resistance isolates showed above $2000{\mu}g/ml$. Resistant isloates also showed cross resistance among strobilurin group fungicides and low control efficacy in the field test. These results suggest that treatment of strobilurin fungicides should be reduced for the control of powdery mildew.