• Korean Journal Plant Pathology
• /
• v.11 no.3
• /
• pp.282-284
• /
• 1995

Grey leaf spot on tomato plants was first observed in Sedo-myeon, Puyo-kun, Chungnam province of Korea in 1994. This disease which had not been reported before in Korea exhibited different symptoms from those of other leaf spot diseases on tomato plants. The symptoms were characterized by small irregular-shaped spots on leaves at the initial stage of the infection, subsequent spread and coalescence of the spots throughout the leaves with ultimate necrosis, and abscission from the plants. When healthy tomato plants were inoculated with a conidial suspension of the fungus isolated from the lesion of a diseased plant in a field, the same characteristic symptoms as those in the field were produced. Furthermore, the same pathogen could be reisolated from the lesions formed buy the inoculation. Conidial characteristics of the pathogen were as follows; oblong shape with constricted 3 transverse septa, round-shaped base, round- or point-shaped apex, size of 45~75$\times$12.5~17.5 ${\mu}{\textrm}{m}$, and 3.5 : 1 ratio of length to width. The pathogen was identified as Stemphylium lycopersici and thus this is the first report on the occurrence of grey leaf spot disease on tomato plants caused by s. lycopersici in Korea.

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

• International Journal of Industrial Entomology and Biomaterials
• /
• v.22 no.1
• /
• pp.11-15
• /
• 2011

Impact of pruning date, shoot age and weather parameters on the severity and development of grey leaf spot (Pseudocercospora mori) of mulberry was studied. The disease severity (%) increased with increase in shoot age irrespective of pruning date. Maximum disease severity was observed in plants pruned during second week of October and minimum in plants pruned during last week of December. Significant (P<0.05) influence of date of pruning, shoot age and their interaction was observed on the severity of the disease. Apparent infection rate (r) was significantly higher during plant growth period from day-48 to day-55. Average apparent rate was higher in plants pruned during first week of September and least in plants pruned during third and fourth week of December. Multiple regression analysis revealed contribution of various combinations of weather parameters on the disease severity. A linear prediction model [$Y=66.05+(-1.39)x_1+(-0.219)x_4$] with significant $R^2$ was developed for prediction of the disease under natural epiphytotic condition.