• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.210-216
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• 1995

Alternaria spp.were predominantly isolated from the abnormal leaf spot lesions of pear cultivars Niitaka and Nijiiseiki. Alternaria isolates from the cultivar Niitaka were not pathogenic to both cultivars, but the isolates from the cultivar Nijiiseiki developed typical lesions of black leaf spots and were identified as A. kikuchiana. However, no typical abnormal leaf spot lesions were produced by the Alternaria isolates. Foliar spray of twelve different agrochemicals including lime sulfur, either alone or in combinations, with 7 times applications from April to July failed to reduced the disease development. Application of 17 different pesticides including fungicides, insecticides and herbicides currently used in pear orchards did not cause leaf injury similar to the abnormal leaf spot. Simulated acid rain of as low as pH 3.0 did not incite any leaf lesions alike the abnormal spot lesions. Mineral contents in the leaves of both cultivars did not differ significantly between the healthy leaves and those with abnormal leaf spots. When cuttings of pear tree were obtained in February from newly emerged twigs of the healthy or the diseased trees of Niitaka and planted in sand in the greenhouse, only those from the diseased trees developed typical leaf lesions of the abnormal spot. These results indicate that abnormal leaf spots are caused by unknown systemic agents in pear trees, rather than by Alternaria spp., chemical injury or acid rain.

• Korean Journal Plant Pathology
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• v.10 no.3
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• pp.169-174
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• 1994

A new unidentified pear leaf spot disease presumed to first occur in the late 1970's has recently become prevalent over the pear growing areas, and caused the greatest problem for pear production in Korea. The disease began to develop on pear leaves at mid- to late May, peaked at mid- to late une, but stopped further development until September in cool climate. Leaf lesions are 0.9∼2.5 mm in diam., oval or irregular to rectangular in shape, first appeared reddish purple, later changed to dark brown, and to whitish grey in the late season. Lesions were limited to appear only on the mature, hardened leaves, initially from leaf margin or near the leaf veins, and later scattered over the leaf surface. Individual lesions usually did not enlarge, but often coalesced each other, commonly causing shot holes and eventual early falling. The disease was most severe on the major pear cultivars Niitaka and Okusankichi ranged with 4 to 100% infections in trees, depending on the orchards, but not on the cultivar Chojuro. Damages from the disease included lower fruit weight, and higher acid and less sugar content in fruits, resulting in lowering the overall fruit quality. Etiology of the disease including identification of the causal organism is in a separate paper.

• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.217-223
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• 1995

Nature of graft transmissibility of pear abnormal leaf spot disease was examined by various grafting methods in the greenhouse and field. When the diseased and symptomless twigs were collected in winter and grafted in the next spring to the seed-originated healthy root stock, the abnormal leaf spot was developed only in the case of the diseased twigs. Double grafting on a seed-originated healthy root stock, where the diseased and the symptomless twigs were used as 1st and 2nd scions, respectively, developed abnormal leaf spot lesions without exception on the 2nd scions. Tongue-graft with the diseased and the symptomless trees also incited abnormal leaf spots on the both trees. Abnormal leaf spots of were also developed on HN-39, an indicator pear tree, used as a 2nd scion in a double graft test, where the diseased twig and a seed-originated healthy tree were used as the 1st scion and the root stock, respectively. When the diseased twig was top-grafted to the healthy root stock, lesion development of abnormal spot was limited to the grafted twig itself in the 1st year, but expanded to the main branches in the 2nd year, and spread over the whole tree in the 3rd year. This result indicates that the causal agent of abnormal leaf spot disease is transmitted by graft.

• Research in Plant Disease
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• v.8 no.4
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• pp.254-257
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• 2002

It was conducted to investigate an effective control measure of the black necrotic leaf spot disease on pear, The disease commonly occurred in major cultivation areas of Korea revealed 5.6 ％ infection rate on the widely growing cultivar Niikata. The disease substantially reduced yield and quality of pear fruits, however, it has never been controlled by chemicals. Renewal of the pear trees to resistant cultivar was found to be the most effective to control the disease. As a result, the disease did not developed for 2 years on the diseased Niikata that was top-grafted with resistant cultivars Soowhang and Whasan. lop-grafting with resistant cultivars was recommended far the pear trees showing over 80％ infection rate and lower than 70% fruit yield compare to standard production.

• The Plant Pathology Journal
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• v.21 no.2
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• pp.164-166
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• 2005

Corynespora leaf spot occurred severely on balsam pear (Momordica charantia) at Changwon, Gyeongnam province in Korea in November and December 2003. The causal fungus isolated from infected leaves of the plants grew well on potato dextrose agar showing gray to brown color. Solitary or catenary conidia of the fungus were obclavate to cylindrical in shape, and pale olivaceous brown or brown in color. The number of isthmus pseudosepta ranged from 4 to 20 and measured 36~186${\times}$8~19 ${\mu}m$ in size. Conidiophores were pale to light brown in color and measured 94~648${\times}$3~8 ${\mu}m$ in size. Optimal temperature for mycelial growth was $30{\circ}C$. On the basis of mycological characteristics and pathogenicity, the fungus was identified as Corynespora cassiicola (Berk. & Curt.) Wei. This is the first report on the corynespora leaf spot of M. charantia caused by C. cassiicola in Korea.

• Korean Journal Plant Pathology
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• v.12 no.3
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• pp.363-367
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• 1996

배나무잎 이상반점증상의 이병여부를 조기에 판별할 수 있는 가장 간편한 검정방법을 개발코자 시험하였다. 접목시기는 늦어질수록 병징발현율이 감소하였다. 접목방법은 2중절접, 2중삭아절접 순으로 양호하였으나 숙련된 기술이 필요한 이중절접방법보다 간편한 2중삭아절접 방법이 대량검정에 적합하였다. 이상반점증상의 전염에 필요한 최소 접촉시간은 1일 이상이었고 칼루스가 형성되어 접목부위가 활착된 21일 이후에서 발병이 가장 높았다.

• Horticultural Science & Technology
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• v.19 no.1
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• pp.43-47
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• 2001

This study was conducted to investigate the integrated control strategy against pear black leaf spot disease. Using indicator plant PS-95 we selected six virus-free trees (cv. Niitaka) from commercial orchards in the major pear production area. Disease symptom by pear black leaf spot in the shoot of pear (Niitaka) has been successfully inhibited by heat treatments for 3 weeks at temperature of $40^{\circ}C$ (day) and $32^{\circ}C$ (night) or 4 weeks at $37^{\circ}C$ and $30^{\circ}C$, respectively. However, survival rate of the shoot tips on stocks was low. Seven cultivars Niitaka, Imamura- aki, Waseaka, Nijisseiki, Wasenijisseiki, Shinsetsu and Whangkeumbae produced visible symptoms in the first year after inoculation with the virus. Other 11 selections remained symptomless. Two resistant cultivars Suwhangbae and Gamcheonbae were selected, which showed high fruit quality. It is recommended that these cultivars could be top-grafted onto the infected Niitaka trees to overcome the damage caused by the disease in the orchard.

• Korean journal of applied entomology
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• v.7
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• pp.61-64
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• 1969

By way of paper chromatography, free sugars in pycnial drops of Gymnosporangium haraeanum Sydow were investigated in regard of their biochemical interrelation with free sugars of Chinese juniper and pear leaf. The free sugar in pycnial drops of Gynnosporangium haraeanum Sydow were identified to only Fructose spot. Free sugars in Chinese juniper leaf were identified to Glucose. Galactose and two unknown spots. Free sugars of another sample in pear leaf were identified to spots of Glucose, Furctose and Galactose. The Arbutin from pear leaf was crystalized and its structure was identified to Glucose and Hydroquinone. The acetone powder of Emulsin was incubated for 1 hour at $40^{\circ}C$ with 0.05 M Arbutin substrate in test tube and purified by general method with the purpose of analysis of its. metabolic products. And the paper chromatographic analysis showed it to be Glucose spot. From the above results, this Fructose in pycinal drops of Gymnosporangium haraeanum Sydow is presumed to be the exchangeable from free sugars in pear leaf or to be the hydrolyzed of $\beta-glycoside$ (Arbutin)-the metabolic isomerization of Glucose into Fructose by pycnia isomerase.

• Korean Journal Plant Pathology
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• v.12 no.2
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• pp.214-218
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• 1996

배나무잎 이상반점증상의 보독여부를 신속정확하게 검정할 수 있는 목본 지표식물을 선발하기 위해 시험을 수행하였다. 신고x조생적 등 5개 교배조합 102개체를 공시해서 1차로 10개체를 선발하였다. 1차로 선발된 개체중에서 전형적인 이상반점증상이 조기에 잘 나타나고 이상반점증상과 유사한 검은무늬병에 저항성인 신고$\times$조생적 86-2-2 계통을 최종선발하였다. 선발된 지표식물을 사용하여 농가포장에서 이상반점 증상의 보독여부를 실증시험한 결과 보독유무의 조기판별이 가능하였다. 이상의 결과에서 최종 선발된 신고$\times$조생적 86-2-2계통을 PS-95로 명명하고자 한다.

• Korean Journal Plant Pathology
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• v.12 no.2
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• pp.209-213
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• 1996

배나무잎 이상반점증상의 발병환경 조건을 조사하고자 실험한 결과 주간 23$^{\circ}C$, 야간 18$^{\circ}C$ 온도조건에서 병징발현이 가장 심하였고 이보다 높은 온도인 28/23$^{\circ}C$와 낮은 온도인 18/13$^{\circ}C$에서는 발병이 아주 적었다. 배나무잎에 봉지를 피복하면 발병이 전혀 없거나 극히 저조하였다. 이것은 봉지내의 온도가 최고 46.8$^{\circ}C$까지 올라가 고온에 의하여 발병이 억제된 것으로 생각된다. 이병주 토양과 건전주 토양의 화학성을 조사한 결과 이병주 토양에서는 건전주 토양보다 유효인산량이 많게 나타났다. 토양수분이 많거나 적었을 때는 병징발현이 다소 늦어지기는 하나 최종 조사시 발병정도는 큰 차이를 나타내지 않았다.