• Mycobiology
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• v.28 no.1
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• pp.54-56
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• 2000

A black scab disease occurred on sword bean (Canavalia gladiata) in plastic film houses around Chinju area during the spring season of 1999. The disease started from flower bud, then moved to flower stalk, pod, petiole, cirrus, stem and leaves. The lesions started with small dark brown spots then were gradually expanded. Severely infected plants reached 37.4% of whole plant covered with scab. Numerous conidia were produced on the diseased flower disk, pod, floral axis, stem and leaves. Most of the conidia were appeared to be readily dispersed in the air, but the mycelia were not suggested causing of sooty mold by ectoparasitism. A fungus was isolated from the diseased stem, and inoculated to healthy plants to satisfy the Koch's postulates and proved the fungus was the causal agent of the disease. The isolated fungus grew on potato dextrose agar, forming greenish black to pale brown colonies. Conidia were ellipsoidal, fusiform or subspherical, mostly one-celled but occasionally septated. The conidia were $3.9{\sim}34.1{\times}2.7{\sim}5.1\;{\mu}m$ in size and formed in long branched chains on the erected conidiophores which were pale olivaceous brown and variable in length between $7.2{\sim}210.7\;{\mu}m$ in size. Ramoconidia were $7.6{\sim}29.2{\times}3.2{\sim}14.4\;{\mu}m$ in size. The fungus was identified as Cladosporium cucumerinum based on the above morphological characteristics. The optimum temperature for mycelial growth and conidial formation was about 15 to $25^{\circ}C$. Cladosporium scab of sword bean caused by the fungi has not been reported in Korea previously.

• Research in Plant Disease
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• v.10 no.2
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• pp.135-137
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• 2004

It was conducted to select the resistant potato cultivars to common scab, to replace the existing susceptible cv Dejima in Jeju island conditions both 1997 and 2001. Among cultivars, cvs Jemchip, Alpa, Atlantic and Jopung were more resistant than others in the field with both low and high incidence of the disease. Also among the existing cultivars grown in Korea, cvs Superior, Jopung and Chubaek were resistant, expecially in terms of production of marketable potatoes.

• The Plant Pathology Journal
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• v.39 no.2
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• pp.228-233
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• 2023

Two pear cultivars with different degrees of resistance to Venturia nashicola were evaluated on the basis of a disease severity rating for pear scab resistance under controlled environmental condition. Two inoculation techniques were tested: the procedure for inoculation by dropping conidia suspension of V. nashicola; the procedure by deposition of agar plug on the abaxial surface of pear leaves. All tested cultivars resulted in blight symptoms on the inoculated leaves and became spread to uninoculated region or other leaves. Although both methods provide satisfactory infection of V. nashicola on pear leaves, the mycelial plug method of inoculation was more reliable than the spray inoculation method for the evaluation of pear scab disease resistance. The incubation period of V. nashicola in the resistant pear cultivar, Greensis was longer than that in the susceptible cultivar, Hwasan.

• The Korean Journal of Mycology
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• v.13 no.4
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• pp.263-265
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• 1985

To identify a causal organism of pear scab in Korea, pathogens were isolated from pears of different varieties. Venturia nashicola was found to be the pathogen of the scab disease in Korea.

• The Korean Journal of Pesticide Science
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• v.18 no.4
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• pp.434-438
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• 2014

The mixture of fluxapyroxad plus pyraclostrobin or the 9 time-spray schedule with various fungicides was evaluated for their efficacy in controlling pear scab in field trials. It showed sufficient condition to evaluate the efficacy of fungicides for the control of pear scab since disease incidence of the untreated control plot was 58.4% or 100% on leaves or fruits, respectively. Pear scab on leaves was occurred by 6.3% at treated plot with the mixture of fluxapyroxad plus pyraclostrobin, resulting in the 89.2% of control value. Incidence of the fruit disease was 16.7% at treated plot with the mixture of fluxapyroxad plus pyraclostrobin, showing 83.3% of control value. When the 9 time-spray schedule was tested, pear scab was occurred by 5% or 13.3% on leaves or fruits, respectively. Their control values were the 91.4% on leaves or 86.7% on fruits. Although the 9 time-spray schedule showed slightly lower disease incidence than the mixture of fluxapyroxad plus pyraclostrobin, but there is no statistically significant difference. These results suggest that the mixture of fluxapyroxad plus pyraclostrobin can control effectively the pear scab.

• Journal of Environmental Science International
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• v.32 no.11
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• pp.777-788
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• 2023

Potato common scab disease is caused by pathogens belonging to Streptomyces spp. and results in a serious yield loss worldwide. Despite decades of research aimed at disease management, a definitive control method remains undiscovered. This study aims to explore the correlation between the C/N ratio and urea application with potato common scab pathogen dynamics and disease severity. We applied sawdust with a high C/N ratio and urea into the soil prior to potato cropping, both in pot and field experiments. Disease severity assessments and quantification of the TxtB gene were conducted at the harvest stage. Furthermore, culture experiments were performed to assess the direct impact of urea on the pathogen. Our findings revealed that higher disease severity was correlated with a high C/N ratio application and pathogenic gene quantity. Urea exhibited a direct influence on S. scabiei activity, reducing the disease severity in pot experiments. However, the effects of urea application on disease suppression in the conductive field were inconclusive. Although the results of urea application experiments displayed inconsistencies between pot and field trials, urea worked as the control to suppress S. scabiei activity. Further investigations are needed under various field conditions to confirm these findings.

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.162-165
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• 2005

Potato scab, an important disease that affects developing tubers, causes a major problem in potato cultivation. The major potato cultivation areas in Korea are located in two Northern provinces, Gangwon and Gyeonggi, and two Southern provinces, Jeju island, and South Jeolla. In these areas, potato scab is widely distributed and has caused severe problem in potato cultivation. Therefore, potato-growing areas were surveyed for identification and distribution of potato scab pathogens from 1996 to 1999. Pathogenic Streptomyces strains were isolated from potato scab lesions and six representative Streptomyces species were characterized based on their phenotypic and molecular characteristics including, pathogenicity, physiological and morphological properties, analyses of 16SrRNA genes and 16S-23S ITS region, DNA relatedness, production of thaxtomin A, and the presence of nec1 and ORFtnp gene homologs. Three species were identified as previously described Streptomyces scabies, S. turgidiscabies, and S. acidiscabies, while other three species having distinct phenotypics properties were identified as novel S. luridiscabiei, S. puniciscabiei, and S. niveiscabiei.

• The Plant Pathology Journal
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• v.33 no.5
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• pp.450-457
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• 2017

Scabs caused by Venturia carpophila greatly reduce the quality of the fruits of the Japanese apricot (Prunus mume) when the disease is not properly managed. The disease produces a superficial blemish that is unlikely to affect the overall yield of processed fruit, but reduce the value of fruit intended for the fresh market. Incidence rates of scab at sprayed and unsprayed orchards range from 0% to 21.5% and from 30.2% to 100%, respectively, in the major cultivation regions of Jeonnam Province during the growing season of 2009. The trends in disease progress were quite similar, regardless of regions, and cultivar Namgo was relatively less damaged by scab compared to cultivar Cheonmae among the tested Japanese apricot cultivars. The fruits on branches 1.5 m above the infected Japanese apricot trees and the stem-end parts of the infected fruits were more severely damaged by scabs, possibly because of rain and run-off facilitate dissemination of conidia of V. carpophila and subsequent infection of the fruits or branches. The conidia of V. carpophila were dispersed from March 24 to April 26 in 2010, and more conidia were dispersed from 2-year-old branches than 1-year-old branches. Since the control efficacies were higher than 90% after more than two applications of Trifloxystrobin WG at 10-day-intervals from mid April, it is that effective fungicides be applied at least two times at 10-day-intervals from the middle of April to manage scabs of Japanese apricot in orchards.

• Research in Plant Disease
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• v.29 no.2
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• pp.101-107
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• 2023

Pear scab, caused by Venturia nashicola, is one of the most devastating diseases of Asian pears in Korea, Japan, China, and Taiwan. To manage this disease, growers mainly relied on chemical control. However, continuous use of chemical causes not only environmental contaminant but also the emergence of resistance to pathogens, so a more sustainable management plan is needed. Therefore, it is necessary to understand the life cycle and infection characteristics of V. nashicola and to set an active control strategy according to meteorological conditions rather than, as in the past, calendar-based control or continuous use of a specific fungicide system. Various results of the related research results were reviewed to summarize the race, infection characteristics, and control system of V. nashicola, a pear scab, and to discuss plans for a more effective control system.

• Korean Journal of Plant Resources
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• v.32 no.4
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• pp.296-302
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• 2019

This study was accomplished to select breeding materials among the pear germplasm 6 species 43 accessions and check out the expression of scab incidence of inter specific hybrids of 5 crosses 609 seedlings for scab resistance breeding. Fruitlets scab incidence of P. pyrifolia, P. bretschneideri and P. ussuriensis were 59.5, 73.4 and 63.0% respectively, and also fruitlets scab incidence of interspecific hybrid cultivars between P. pyrifolia and P. bretschneideri were 77.7%. However, fruitlets scab incidence of P. communis and interspecific hybrid accessions between P. pyrifolia and P. communis were significantly less than 15%. As a result of the Duncan test, scab resistance of pear accessions were classified into two groups: P. communis and their hybrid were resistance and P. bretschneideri, P. pyrifolia, P. ussuriensis, and among their hybrid were susceptible. Also, it showed the same trend in the seedlings. Scab incidence of 'Seolwon' ${\times}$ 'Chuwhangbae' and 'Supergold' ${\times}$ 'Mantienhong' in P. pyrifolia seedlings showed more than 80%, while that of interspecific hybrid between P. pyrifolia and P. communis showed about 2%. It showed scab resistance of P. communis transferred to hybrid seedlings and expressed to be dominant in their seedlings. Namely, P. communis was good breeding materials for scab resistance.