Apple blotch caused by Marssonina coronaria is a severe disease occurring worldwide as well as in Korea. Occurrence and ecological characteristic of apple blotch were investigated from 2011 to 2013 in five different orchards located in Gyeongbuk province. Two apple cultivar ''fuji'' and ''Gamhong'' were found infected by M. coronaria in later July due to suitable environment and high rainfall. The isolation and growth of M. coronaria on potato dextrose agar (PDA) was not easy, therefore pippet and spread method was developed for conidia collection and suitable nutrient media for fungal growth were improved by using nutrients like mannose and bactopeptone amendid media. To identifiy genetic charateritics, 27 isolates of Marssonina coronaria were colleted from Yeongju, Cheongsong, Daegu, Yeongcheon, Mungyeong and Gunwi regions in Gyeongbuk province. On the basis of ITS spacer regions, 28S rDNA gene and β-tubulin gene sequence analysis, all the isolates were found over 99.0% similar and phylogenetic analysis showed that these isolates were very closely related to each other. The mitochondrial (mt) genomes of M. coronaria have been sequenced for first time and found is a circular 77,932 bp with GC content of 29.8% having genes for encoding ATP synthase subunits, cytochrome oxidase subunits and NADH dehydrogenase subunits. Morphological and histological structures of apple blotch diseases leaves and apple blotch like symptoms were observed for first time by using stereo and light microscope. Black acervuli and mycelia were found on apple blotch diseased leaves. However, such characteristics were absent in the apple blotch like symptoms leaves. Rapid sensitive detection method was used for the first time using two different genes genes internal transcribed spacer (ITS) region and putative metallopeptidase gene. PCR primer sets were designed as Mar-F/Mar-R and Mar-M-F/Mar-M-R, amplified 200 bp and 250 bp DNA fragments that confirmed DNA fragments were amplified from Apple blotch diseased leaves while apple blotch like symptoms leaves showed no amplification. Overwinter survival in field such as as young leaves, stems, bark, soils and weeds were also observed in April and only leaves were found infected. For early diagnosis of apple blotch disease two different diagnostic method optical coherence tomography (OCT) and loop-mediated isothermal amplification (LAMP) were introduced for the first time. LAMP primer sets were designed by using Primer Explorer V4 software. The optimal reaction condition was found 60℃ for 50 min. Application of LAMP assay was performed on 10 different areas cultivated apples in Gyeongbuk and Gyeongnam Provinces from June to July. As a results M. coronaria pathogen was detected in all infected leaves collected from different areas while no LAMP products were detected in healthy leaves The LAMP was applied in field and over 600 samples of apple leaves were diagnosed from 2013 to 2014 in Korea. As a result, Over 30% of these samples were found infected by M. coronaria. These results suggested that the LAMP assay is an innovative, rapid and sensitive technique use for detection of M. coronaria in infected as well as in latent period in apple leaves. LAMP assay is rapid and sensitive technique to detect M. coronaria in both infected and latent period in apple leaves.This technique can be widely used to find the primary infection as well as pathogen in overwinter place and estimate infection period.