• Mycobiology
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• v.42 no.4
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• pp.376-384
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• 2014

Roselle (Hibiscus sabdariffa L.) is one of the most important medicinal crops in many parts of the world. In this study, the effects of microelements, antioxidants, and bioagents on Fusarium oxysporum, F. solani, and Macrophomina phaseolina, the causal pathogens of root rot and wilt diseases in roselle, were examined under field conditions. Preliminary studies were carried out in vitro in order to select the most effective members to be used in field control trials. Our results showed that microelements (copper and manganese), antioxidants (salicylic acid, ascorbic acid, and EDTA), a fungicide (Dithane M45) and biological control agents (Trichoderma harzianum and Bacillus subtilis) were significantly reduced the linear growth of the causal pathogens. Additionally, application of the previous microelements, antioxidants, a fungicide and biological control agents significantly reduced disease incidence of root rot and wilt diseases under field conditions. Copper, salicylic acid, and T. harzianum showed the best results in this respect. In conclusion, microelements, antioxidants, and biocontrol agents could be used as alternative strategies to fungicides for controlling root rot and wilt diseases in roselle.

• The Plant Pathology Journal
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• v.38 no.6
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• pp.616-628
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• 2022

Resistance to pyraclostrobin due to a single nucleotide polymorphism at 143rd amino acid position on the cytochrome b gene has been a major source of concern in red pepper field infected by anthracnose in Korea. Therefore, this study investigated the response of 24 isolates of C. acutatum and C. gloeosporioides isolated from anthracnose infected red pepper fruits using agar dilution method and other molecular techniques such as cytochrome b gene sequencing, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and allele-specific polymerase chain reaction (PCR). The result showed that four isolates were resistant to pyraclostrobin on agar dilution method and possessed GCT (alanine) codon at 143rd amino acid position, whereas the sensitive isolates possessed GGT (glycine). Furthermore, this study illustrated the difference in the cytochrome b gene structure of C. acutatum and C. gloeosporioides. The use of cDNA in this study suggested that the primer Cacytb-P2 can amplify the cytochrome b gene of both C. acutatum and C. gloeosporioides despite the presence of various introns in the cytochrome b gene structure of C. gloeosporioides. The use of allele-specific PCR and PCR-RFLP provided clear difference between the resistant and sensitive isolates. The application of molecular technique in the evaluation of the resistance status of anthracnose pathogen in red pepper provided rapid, reliable, and accurate results that can be helpful in the early adoption of fungicide-resistant management strategies for the strobilurins in the field.

• The Plant Pathology Journal
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• v.39 no.6
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• pp.614-624
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• 2023

Botrytis cinerea is a major fungal plant pathogen that causes gray mold disease in strawberries, leading to a decrease in strawberry yield. While benzimidazole is widely used as a fungicide for controlling this disease, the increasing prevalence of resistant populations to this fungicide undermines its effectiveness. To investigate benzimidazole resistant B. cinerea in South Korea, 78 strains were isolated from strawberries grown in 78 different farms in 2022, and their EC₅₀ values for benzimidazole were examined. As a result, 64 strains exhibited resistance to benzimidazole, and experimental tests using detached strawberry leaves and the plants in a greenhouse confirmed the reduced efficacy of benzimidazole to control these strains. The benzimidazole resistant strains identified in this study possessed two types of mutations, E198A or E198V, in the TUB2 gene. To detect these mutations, TaqMan probes were designed, enabling rapid identification of benzimidazole resistant B. cinerea in strawberry and tomato farms. This study utilizes TaqMan real-time polymerase chain reaction analysis to swiftly identify benzimidazole resistant B. cinerea, thereby offering the possibility of effective disease management by identifying optimum locations and time of application.

• Korean Journal of Medicinal Crop Science
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• v.21 no.5
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• pp.388-393
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• 2013

This study was conducted to select environmental friendly organic materials for controlling the ginseng alternaria blight and to evaluate their effects from 2011 to 2012. Alternaria blight is caused by Alternaria panax and is the most common ginseng disease in Korea. Environmental friendly organic materials were used to reduce amount of chemical fungicides and the number of spray for control of Ginseng Alternaria leaf blight. In 4 years of ginseng, control value of Alternaria leaf blight by single application of Defenoconazole WP was 82.3% and those of single application was 62.0~75.9%. Consequently, mixed or alternated application of eco-material products could be recommended as a control method to reduce the amount of fungicides.

• Journal of Ginseng Research
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• v.26 no.1
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• pp.10-16
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• 2002

In replicated field trials, the efficacy of pentachloronitrobenzene (PCNB; quintozene) for control of damping-off of ginseng seedlings was found to be affected by timing of application and formulation. Application at the time of seeding and prior to placement of straw mulch was found to provide the moat consistent level of disease control. However, decline in plant stand during the four-year production cycle resulted in most treatments providing similar levels of plant populations at harvest. Soil residues of pentachloronitrobenzene were generally highest (1 $\mu\textrm{g}$ PCNB/g soil) in those treatments that exhibited the highest levels of disease control in the seedling year. Straw contained high levels of quintozene after application. Beet seed assays with artificially-infested soils indicated that current use rates provide an amount of product suitable for high levels of disease control.

• Research in Plant Disease
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• v.20 no.1
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• pp.31-36
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• 2014

Alternative spraying was developed using fungicides and potassium phosphonate to control watermelon powdery mildew (WPM) caused by Sphaerotheca fusca under greenhouse condition. In 2010 trial, a total of 9 combinations of 6 fungicides which are legally registered in Korea and currently used on watermelon farms were tested for the control efficacy against WPM. Though the combination of chlorothalonil (Chl)-myclobutanil (My)-fenarimol (Fen)-hexaconazole (Hex) was the most effective (82.6%) in the first-year trial, it had the problem that My, Fen and Hex have the same mode of action. Therefore, in the second-year trial to improve the fungicide combination and to reduce fungicide application, fungicides and potassium phosphonate (P) combinations were tested for WPM control using 500 ppm aqueous potassium phosphonate solution which is both eco-friendly and showing different mode of action from the fungicides tested. The P-My-Fen-Hex applied at 10-day intervals provided relatively high control (75.6%), whereas Chl-My-Fen-P provided 31.8% control. To improve the control, fungicides and P were applied at 7-day intervals in the third-year trial. Though Chl-My-Fen-Hex provided the highest control (89.6%), P-My-Fen-Hex also provided relatively high control (83.5%) compared to 65.9 % control with Chl-My-Fen-P, which suggests that Chl-My-Fen-Hex could be replaced with P-My-Fen-Hex for WPM control.

• 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.

• Research in Plant Disease
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• v.9 no.4
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• pp.205-208
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• 2003

Fungicides of tebuconazole wp, iprodione wp and flusilazole wp were applied for the control of postharvest fruit rots of kiwifruit (Actinidia deliciosa) in the field in 2000 and 2001. More than 3 consecutive applications of these fungicides from the late June with 10-day-interval successfully controlled the diseases. It was found in the field trial in 2002 that 4 consecutive spays from mid of June with 10-day-interval was found to be the most effective application program for tebuconazole wp, iprodione wp and flusilazole wp, The results suggested that currently registered fungicides of benomyl wp and thiophanate-methyl wp can be substituted by tebuconazole wp, iprodione wp and flusilazole wp for the control of the diseases in Korea. Use of these fungicides can restrain emergence of fungicide resistant strains of postharvest fruit rot pathogens with benefit of reduced application of chemicals for food safety and environmental conservation.

• The Plant Pathology Journal
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• v.32 no.6
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• pp.528-536
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• 2016

Although many fungicides are registered for use to control powdery mildew on cucurbits, management of resistance to fungicides in pathogen populations still remains a major challenge. Two biopesticides Regalia SC and HMO 736 were evaluated in the greenhouse and field for their efficacy against powdery mildew in squash. In greenhouses, Regalia SC alone significantly (P < 0.05) reduced powdery mildew compared to the nontreated control, and was as effective as the chemical standard Procure 480SC (triflumizole). In alternation with Procure 480SC, Regalia SC demonstrated greater or equivalent effects on reducing the disease. HMO 736 alone showed varying levels of disease control, but alternating with Procure 480SC significantly improved control efficacy. In addition, application of Regalia SC or HMO 736 each in alternation with Procure 480SC significantly increased the chlorophyll content in leaves and the total fresh weight of squash plants, when compared with the water control, Regalia SC and HMO 736 alone. In field trials, application of Regalia SC and HMO 736 each alone significantly reduced disease severity in one of two field trials during the early stage of disease development, but not during later stages when disease pressure became high. Both Regalia SC and HMO 736 each applied in alternation with Procure 480SC significantly improved the control efficacy compared to Procure 480SC alone. Results from this study demonstrated that an integrated management program can be developed for powdery mildew in squash by integrating the biopesticides Regalia SC, HMO 736 with the chemical fungicide Procure 480SC.

• The Korean Journal of Pesticide Science
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• v.12 no.4
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• pp.375-381
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• 2008

A new disease causing skin sooty dapple symptoms on fruits, leaves, and young shoot of Asian pear occurred in Korea. However, no chemical control approaches has been developed to control this disease. To investigate ecological aspects of this disease, we conducted field surveys in the high or low disease occurred orchards. The years with heavy rainfall caused severe occurrence of the skin sooty dapple disease than the years with lower rainfall during all growth stages of pear fruit. Different fruit-wrapping bags did not prevent occurrence of skin sooty dapple disease, and lesion numbers were higher in lower parts of fruit equatorial line inside of fruit-wrapping bags. There is a direct correlation between occurrence of the skin sooty dapple disease and frequency of fungicide application in the orchards. Among the tested commercial fungicides, thiophanate-methyl WP and penconazole WP completely inhibited the growth of the Cladosporium sp. in in vitro studies but little protection was observed in the field following fungicide applications. However, application of lime sulfur combined with the use of fruit-wrapping bags most effectively reduced incidence of the disease in the field. Our results suggest that skin sooty dapple disease could be a serious problem in sustainable organic pear farms and effective control methods for this disease urgently required.