• Research in Plant Disease
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• v.8 no.4
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• pp.239-244
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• 2002

Among 34 isolates of Colletotrichum spp., 20 from red pepper and 14 from apple, only one isolate 2001-45 was identified as the isolate resistant to sterol biosynthesis inhibiting fungicides. EC$_{50}$ values of the isolate 2001-45 were 153.5, 42.7, 34.0, and 17.1 $\mu\textrm{g}$/ml for myclobutanil, tebuconazole, hexaconazole and nuarimol, respectively, The resistance factor of the isolate 2001-45 against the other isolate 2001-44 to 4 above fungicides was ranged from 17 to 57. However, EC$_{50}$ value of the 2001-45 for prochloraz was 0.07 $\mu\textrm{g}$/ml, which was lower than those of the 2001-44 and the isolate JC24. For the fitness test of the 2001-45, mycelial growth, sporulation on PDA and pathogenicity on fruits were investigated. No difference in mycelial growth was found between 2001-45 and 2001-44, but great difference in sporulation. No symptom was developed by 2001-45 even by wound inoculation of pepper fruit. Therefore, this study indicated that the isolate 2001-45 was inferior to the other isolates in the fitness, although the isolate 2001-45 was highly resistant to sterol biosynthesis inhibiting fungicides.

• The Plant Pathology Journal
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• v.20 no.4
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• pp.244-246
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• 2004

Sectors of rice blast fungus, Pyricularia grisea, frequently appeared on potato dextrose agar amended with edifenphos and iprobenfos. Thus, we assessed the sector-forming frequency of isolates of P. grisea and compared the fungicide sensitivity between wild types and sectors against the fungicides. The 905 isolates of the fungus were obtained from rice-growing locations in Korea from 1997-1998. When the isolates were grown on potato dextrose agar amended with minimal inhibitory concentrations of edifenphos (20 ${\mu}$g a.i./ml)and iprobenfos (55 ${\mu}$g a.i./ml), they produced sectors that overcame the effect of the fungicides. Among the 905 isolates tested, 9.0% produced sectors against edifenphos and 5.6%, against iprobenfos. Different sector-forming frequencies were also observed among the 11 locations of Korea. Sectors obtained from the fungicide-amended media generally grew more than their counterpart wild types grown on the media with either edifenphos or iprobenfos, regardless of their origins. In this study, greater relative growth of sectors over wild types of tested isolates can support the resistant characteristic of the fungus to survive against the fungicides. Therefore, the results indicate that the sectoring in rice blast fungus, P. grisea, may play a role in the occurrence of fungicide resistance.

• Research in Plant Disease
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• v.27 no.4
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• pp.164-171
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• 2021

In August 2020, 377 anthracnose strains were isolated from anthracnose-infected peppers collected from 25 farms in Sunchang-gun, Jeollabuk-do. Inhibition rate of mycelial growth of 11 pepper anthracnose fungicides registered in Korea was investigated for 62 strains selected by region and the degree of susceptibility to each fungicide was investigated. As a result of the fungicide susceptibility test of anthracnose to the fungicide, no resistant strains were observed in fluazinam, prochloraz manganese, and benomyl, but resistant strains appeared in at least three areas for other fungicides, and all strains in all regions were resistant to dithianon. Through this, it was confirmed that the fungicide resistance was expressed in the strain group due to the continuous treatment of the fungicide in some areas. By region, resistant strains to seven pesticides appeared in Sunchang-eup and Paldeok-myeon, and resistant strains to six pesticides appeared in Geumgwa-myeon, Bokheung-myeon, Ssangchi-myeon, Yudeung-myeon, and Pungsan-myeon. There was no significant correlation between fungicide registration time and emergence of resistant strains.

• Mycobiology
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• v.51 no.5
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• pp.333-342
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• 2023

Phytophthora species, classified under Oomycota, cause significant damage to various crops and trees. The present study introduced Phytophthora species, P. nagaii and P. tentaculata, new to Korea, which pose notable risks to their respective host plants. Our research provided a comprehensive description of these species taking into account their cultural features, morphological characteristics, and molecular phylogenetic analysis using the internal transcribed spacer rDNA region and cytochrome c oxidase subunit mtDNA genes (cox1 and cox2) sequences. In addition, this study first evaluated the sensitivity of P. nagaii and P. tentaculata to five anti-oomycete fungicides, finding both species most responsive to picarbutrazox and P. tentaculata resistant to fluazinam. The data can guide targeted treatment strategies and offer insights into effective control methods. The findings expand our understanding of the diversity, distribution, and management of Phytophthora species in Korea.

• The Korean Journal of Pesticide Science
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• v.9 no.4
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• pp.429-436
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• 2005

As Sclerotinia sclerotiorum causing cucumber sclerotinia rot was the fastest in the mycelial growth at $25^{\circ}C$, its pathogenicity was strong at the same temperature among several temperatures. All the isolates of Sclerotinia sclerotiorum showed a strong pathogenicity against cucumber fruits, which was confirmed by a disk assay and a wound assay. A wound assay was superior to a disk assay to develop the assay system for assessing the fungicidal activity of several fungicides against Sclerotinia sclerotiorum. In a disk assay, it was very difficult to assess the fungicidal activity, because the pathogenicity of isolates used in the experiment was very strong. At 500 and $3.0{\mu}g/mL$, the activity of dichloflouanid and the mixture of carbendazim and diethofencarb against cucumber sclerotinia rot was 14.3 and 42.3%, respectively, by using a disk assay. However, at same concentration two fungicides showed the high controlling activity as 100 and 92.5%, through a wound assay in a laboratory. Also, the activity of two fungicides was good against cucumber sclerotinia rot in the greenhouse where cucumber plants were cultivated in the field, showing the control value as 91.1 and 82.9% at 100 and $825{\mu}g/mL$, respectively. All the isolates of Sclerotinia sclerotiorum from cucumber fruits sampled in the polyvinyl house were subjected to monitoring for the resistance to 7 fungicides. The $EC_{50}$ value of 7 fungicides was as follows: fenhexamid; $0.13{\mu}g/mL$, procymidon and iprodione; 0.18 and $0.24{\mu}g/mL$, carbendazim and the mixture of carbendazim and diethofencarb; 0.13과 $0.05{\mu}g/mL$, iminoctadine and dichlofluanid; 1.94 and $8.95{\mu}g/mL$. Ultimately it was not found that resistant isolates of Sclerotinia sclerotiorum were appeared in the field.

• Journal of Mushroom
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• v.9 no.4
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• pp.198-201
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• 2011

Cobweb disease symptoms were observed in a mushroom farm in Buye, Korea during a disease survey in 2008-2011. Five isolates of Cladobotryum sp. were obtained from the infected caps and stipes. These isolates of Cladobotryum sp. were identified as C. mycophilum based on their morphological, cultural characteristics and analysis of the ITS sequences. Early symptoms were noticed as round, fleshy, yellowish brown lesions on mushroom caps. Late symptoms progressed when the parasitic fungus formed white cobweb circular colonies on dead or damaged pinheads, spread on the surface of the casing, and covered entirely fruiting bodies. Optimal temperature and pH for mycelial growth on MEA is $23^{\circ}C$ and 6.0. Microscopically the spores of the fungus are large and most 2~3 celled produced on vertically branched conidiophores. Mushroom caps turned dark brown and shrunk due to soft rot. Testing of sensitivity to selected fungicides showed that isolate was highly resistance to Mancozeb and Thiophanate-methyl, moderately sensitivity to Iprodione, and highly sensitivity to Benomyl, Prochloraz-Mn and Carbendazim.

• The Plant Pathology Journal
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• v.25 no.4
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• pp.317-321
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• 2009

Sensitivity to the new carboxylic acid amide fungicide, mandipropamid, of Phytophthora capsici causing pepper Phytophthora blight was determined on 187 isolates collected in Korea over 3 years, from 2005 to 2007. All isolates were sensitive to mandipropamid, with $EC_{30}$ values for growth of mycelia ranging from 0.001 to $0.037\;{\mu}g/ml$. Among the isolates, 147 (79.0%) isolates were sensitive to metalaxyl, whereas others were resistant to this fungicide. Mandipropamid had the same effect on mycelium growth of both metalaxyl-sensitive and metalaxyl-resistant isolates, indicating an absence of cross-resistance between these two fungicides. Comparison of the sensitivities of P. capsici isolates showed a positive correlation between sensitivity to mandipropamid and dimethomorph ($r^2$=0.8533). The results of this study indicate that there is no evidence for development of resistance to mandipropamid in this population of P. capsici isolates collected in Korea.

• The Korean Journal of Pesticide Science
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• v.4 no.2
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• pp.1-10
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• 2000

Fungicide resistance study in Korea is still in its infancy, and most of those resistance studies are largely limited to newness of the detected resistant strains. In future, detection of fungicide-resistant strains has to be based on sensitivity distribution of pathogen populations to certain fungicides, and standard levels of certain fungicides for resistance should be determined under the basis of this data. Most of the early research on fungicide resistance in Korea has overlooked this point, and resulted in inconsistency and confusion for monitoring sensitivity shift of pathogen population among individual researchers. Fungicide resistance detected in vitro tests has to be documented in field trials by examining control efficacy against resistant and wild-type pathogen populations. Resistance detection in wife has to be correlated with lower activity in practice. Using this process, fungicide resistance will have a practical meaning. Fitness evaluation of resistant strains for survival is, in particular, of importance to determine the future stability of the resistance in the pathogen population. In fields, sensitivity change of pathogen populations should be carefully monitored with and without fungicide selection pressures to establish long-term management strategies against fungicide resistance. It is becoming an urgent task to provide information through research for designing and implementing successful counter-measures against fungicide resistance problems in Korea.

• Research in Plant Disease
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• v.19 no.1
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• pp.7-11
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• 2013

Forty eight isolates of Botrytis elliptica and 23 isolates of B. cinerea from several locations in Korea were tested for resistance to fungicides used in the farmer's fields. Isolation frequency of B. elliptica having $EC_{50}$ (effective concentration of 50%) value $500-1000{\mu}g/ml$ to benomyl and mancozeb appeared highly, suggesting that the two fungicides are not effective in controlling leaf blight of lily in the field. The isolates were tested for resistance to fungicides procymidone and iprodione which were most commonly used in the farmer's fields. The rates of $EC_{50}$ value $5-50{\mu}g/ml$ to procymidome and iprodione were 93.7% and 100%, respectively, and those of $0-0.1{\mu}g/ml$ to diethofencarb+carbendazim and fludioxonil were 98.0% and 93.8%, respectively. In the rain-protected cultivation, control of leaf blight of lily was the most effective when iprodine, diethofencarb+carbendazim, and fludioxonil were sprayed alternately four times during the growing season.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.456-462
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• 2010

Baseline sensitivity to benthiavalicarb, iprovalicarb and dimethomorph included into carboxylic acid amide (CAA) group was evaluated in 180 isolates of Phytophthora capsici over 4 years from 2005 to 2008. $EC_{50}$ (effective concentration inhibiting mycelial growth by 50%) value of benthiavalicarb ranged from $0.015{\mu}g\;mL^{-1}$ to $0.049{\mu}g\;mL^{-1}$ with a mean of $0.033{\mu}g\;mL^{-1}$. The mean values of $EC_{50}$ of iprovalicarb and dimethomorph were 0.411 (0.197 - 0.556) ${\mu}g\;mL^{-1}$ and 0.271 (0.101 - 0.798) ${\mu}g\;mL^{-1}$, respectively. Although there was no increasing tendency in $EC_{50}$of benthiavalicarb and iprovalicarb during 4 years, $EC_{50}$ of dimethomorph was increased gradually by laps of time. There was no cross-resistance between each fungicide used in this study and metalaxyl. Among fungicides included into CAA group, there was a positive correlation between benthiavalicarb and iprovalicarb, and between dimethomorp and mandipropamid.