• Research in Plant Disease
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• v.10 no.2
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• pp.121-125
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• 2004

An epidemic of target leaf spot of cucumber (Cucumis sativus) occurred in commercial greenhouses in Korea in 2000/2001. The early symptoms on the leaves were small brown spots with yellow halos. These lesions became irregular enlarging in diameter and eventually defoliation resulted. The causal agent was a fungus with morphological characteristics matching Corynespora cassiicola. The sequence of the ITS region of C. cassiicola CM2000-1 was identical to that of an authentic strain of Corynespora cassiicola. Optimal germination of spores and mycelial growth on plate was at 3$0^{\circ}C$. A long dew period on the leaf surface and high temperatures were the main contributing factors for disease development and the greenhouse epidemic. Artificial inoculation of the Korean isolate of C. cassiicola revealed resistance in some Korean cucumber cultivars.

• Research in Plant Disease
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• v.24 no.3
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• pp.175-181
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• 2018

Incidence rates of bacterial canker, bacterial leaf spot and postharvest fruit rot on the Korean yellow-fleshed kiwifruit cv. Haegeum were compared with those on the most popular green-fleshed kiwifruit cv. Hayward grown in several naturally infected kiwifruit orchards in 2013 and 2014. The percentages of diseased leaves caused by bacterial canker were 18.5% and 17.3% on Hayward in 2013 and 2014, but those on Haegeum were 1.2% and 0%, respectively. The percentages of diseased leaves caused by bacterial leaf spot on Hayward were 63.5% and 16.2% in 2013 and 2014, respectively, but no bacterial leaf spots were observed on Haegeum in both years. The average percentages of diseased fruits caused by postharvest fruit rot were 24.2% and 20.5% on Hayward in 2013 and 2014, while 6.3% and 4.4% and Haegeum, respectively. Botryosphaeria dothidea was turned out to be the major pathogen of postharvest fruit rot on both cultivars.

• Research in Plant Disease
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• v.13 no.2
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• pp.122-125
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• 2007

Leaf spot disease of Kalanchoe (Kalanchoe blossfeldiana) occurred at the farmer's vinly house in Gangseo-gu, Busan Metropolitan City, Korea, 2006. The diseased plants with typical symptom were collected and the casual agent were isolated. Its mycological characteristics and pathogenicity were examined. The results were as follows. The typical symptoms of the disease appeared as small brownish or dark brown spot on both sides of the leaves. The spots tended to develop from lower leaves. The spots gradually enlarged into conspicuous necrotic lesions 1-5 mm in diameter. Colonies of the causal fungus formed on potato dextrose agar were velvety, gray or grayish brown in color, Conidia were cylindrical or obclavate to oblong in shape, brown in color, $24{\sim}65\;{\times}\;12{\sim}23\;{\mu}m$ in size and had 1-4 transverse septa, The optimum temperature for growth of the fungus was about $25-30^{\circ}C$. Conidiophores were brown in color, $32{\sim}135\;{\times}\;4{\sim}8\;{\mu}m$ in size and had 1-7 transverse septa. The fungus was identified as Stemphylium lycopersici (Enjoji) Yamamoto based on its symptom and mycological characteristics. This is the first report of leaf spot of Kalanchoe caused by S. lycopersici in Korea.

• Research in Plant Disease
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• v.22 no.1
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• pp.50-54
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• 2016

In early June 2014, leaf spot symptoms were observed on black chokeberry (Aronia melanocarpa) in Yesan-gun and Geumsan-gun, Chungcheongnam-do in Korea. The initial symptoms on leave surfaces were brown small-circular spots with a yellow halo lesion, and gradually the small spots were fused, all of infected leaves dropped eventually. A fungus were isolated from the initial lesion, and cultured on potato dextrose agar. Colony color on upper surface of plate varied from olive gray to charcoal gray. Size of conidia mostly extend to $19-50{\times}5-9{\mu}m$ in nature and $20-59{\times}8-13{\mu}m$ in culture, with 3-8 transverse septa and usually no longitudinal septum or only 1 longitudinal septum in 1-3 of the transverse compartments, and also have a short or long beak. Pathogenicity was investigated using wounded or unwounded black chokeberry and apple leaves. After 7 days of inoculation, leaf spots were similar to the symptoms naturally occurred in the field. On the basis of mycological characteristics, pathogenicity, and ITS rDNA sequence analysis, this fungus was identified as Alternaria mali. This is the first report of Alternaria leaf spot on black chokeberry caused by A. mali in Korea.

• The Korean Journal of Mycology
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• v.44 no.3
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• pp.201-205
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• 2016

In August 2015, leaf spot symptoms were observed on Korean gondre thistle (Cirsium setidens) in Youngwol, Korea. During the early stage, the symptoms appeared as one or more small gray-brown to brown spots on plant leaves. The spots showed extensive enlargement over time and eventually became large dark brown to black lesions on the whole leaf. Stemphylium species were consistently isolated from affected leaves. All isolates were identified as S. lycopersici, S. solani, or S. xanthosomatis based on morphological and cultural characteristics. The isolates were confirmed as S. lycopersici based on a multilocus sequence analysis using the ribosomal internal transcribed spacer (ITS) region, elongation factor 1, GAPDH (glyceraldehyde-3-phosphate dehydrogenase), and the noncoding region between the vacuolar membrane ATPase catalytic subunit A gene and a gene involved in vacuolar biogenesis. Pathogenicity was tested by spore suspension inoculation on wounded or unwounded gondre leaves. The lesions were observed on inoculated leaves within 3 days after inoculation, regardless of wound. To our knowledge, this is the first report of the leaf spot on gondre thistle caused by S. lycopersici in Korea or elsewhere.

• The Plant Pathology Journal
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• v.30 no.2
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• pp.125-135
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• 2014

A population model of bacterial spot caused by Xanthomonas campestris pv. vesicatoria on hot pepper was developed to predict the primary disease infection date. The model estimated the pathogen population on the surface and within the leaf of the host based on the wetness period and temperature. For successful infection, at least 5,000 cells/ml of the bacterial population were required. Also, wind and rain were necessary according to regression analyses of the monitored data. Bacterial spot on the model is initiated when the pathogen population exceeds $10^{15}cells/g$ within the leaf. The developed model was validated using 94 assessed samples from 2000 to 2007 obtained from monitored fields. Based on the validation study, the predicted initial infection dates varied based on the year rather than the location. Differences in initial infection dates between the model predictions and the monitored data in the field were minimal. For example, predicted infection dates for 7 locations were within the same month as the actual infection dates, 11 locations were within 1 month of the actual infection, and only 3 locations were more than 2 months apart from the actual infection. The predicted infection dates were mapped from 2009 to 2012; 2011 was the most severe year. Although the model was not sensitive enough to predict disease severity of less than 0.1% in the field, our model predicted bacterial spot severity of 1% or more. Therefore, this model can be applied in the field to determine when bacterial spot control is required.

• Korean journal of applied entomology
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• v.24 no.2 s.63
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• pp.103-106
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• 1985

The present study was carried out to determine appropriate growth stage for evaluating resistance to septoria brown spot in field and to search resistance sources from soybean germ plasm. Disease severity expressed by log $\frac{x}{1-x}$ was different with soybean genotypes and vertical progress of the disease was related to the diseased leaf area. Correlation between diseased leaf area and the area under septoria brown spot disease progress curve (AUBC) was highest at full blooming stage, indicating a reasonable stage for measuring the disease severity to evaluate resistance in field. There was no lines highly resistant to the disease among 1,428 native soybean lines tested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.748-753
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• 2000

Nowadays, many studies and researches in data storage have been carried out and storage capacity is increased. But the limitation of storage capacity is happened for several problems. One of them is spot & pit size in optical and magnetic data storage and another is the resolution of actuators. The problems in spot & pit size is covered by new data storage methods- for example, NFR{Near-Field Recoding) system. But the resolution limit of an actuator doesn't follow up the development of spot & pit size. Because of them, we should improve a resolution of an actuator. Especially, in this paper an actuator is studied and designed for NFR(in using SIL(Solid Immersion Lens) system. It is a dual stage actuator, which consists of a Fine actuator and a Coarse actuator, and should desire 100nm accuracy. But, our actuator system only includes tracking mechanism execpt focusing mechanism which is controlled by slider mechanism used in HDD. Its actuating force generation method is VCM(Voice Coil Motor). The Fine actuator is composed of 4-leaf springs and a bobbin wrapped by coil. The Coarse actuator has Coils and 3-Roller bearings.

• Korean Journal Plant Pathology
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• v.11 no.1
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• pp.90-93
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• 1995

Leaf blotch of Welsh onion was observed at a farmer's field at Kangnung in July 1990. Further collection o the diseased materials was made in 1993 and 1994. The symptom initially appeared as discolored spot and later yellowish blotch with the long axis parallel to the leaf veins, which turned to sooty colored concentric lesion due to heavy production of conidiophores and conidia. Cladosporium allii-cepae (Ranojevic) M. B. Ellis was repeatedly isolated from the leaf lesions. Healthy Welsh onion inoculated with conidial suspension of the fungus produced the typical symptom 10 days after inoculation. Koch's postulates were fulfilled by reisolation of the fungus. This is the first report of a Cladosporium leaf blotch of Welsh onion in Korea.

• International Journal of Industrial Entomology and Biomaterials
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• v.6 no.2
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• pp.139-143
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• 2003

Mathematical constants for multiplication with leaf length (I) or breadth (b) or l ${\times}$ b have been worked out for determining leaf area in promising mulberry genotypes viz., Chinese White, S-146, Chak Majra and Sujanpur Local of sub-tropical India. When pooled, the mathematical constants worked out were 8.1132, 10.1019 and 0.5992 for multiplication with leaf length, breadth and l ${\times}$ b, respectively, for genotypes bearing un-lobbed leaves and 6.9447, 8.2761 and 0.5009 for multiplication with leaf length, breadth and l ${\times}$ b, respectively for genotypes bearing lobbed leaves. Leaf area can be worked out by using any constant by multiplying either with leaf length or breadth or both (l ${\times}$ b). Estimated leaf areas worked out were found significantly and positively correlated with actual leaf area (r＝999$^{＊＊}$). The suggested present non-destructive method by using mathematical constants is very quick and alternative to electronic leaf area meter for spot leaf area determination in mulberry which is the only food source for mulberry silkworm in sericulture industry.