• Korean Journal Plant Pathology
• /
• v.10 no.2
• /
• pp.78-82
• /
• 1994

Unusually severe rice blast epidemic sweeped over the rice growing area in Gyeongnam Province and elsewhere in 1993. Leaf blast infection was reached to 33,133 ha, which is about 24.5% of total paddy area and neck blast infection was apparent throughout 4,421 ha. Major factors affecting such an unusual epidemic appeared to be as follow: Firstly, low temperature, frequent rainfall and coincidentally insufficient duration of sunshine through July and August; Secondly, most cultivars possessing low levels of field resistance were cultivated in wide areas: Thirdly, blast fungus population was enough for successive infection under optimum weather condition and most races distributed in field were able to infect most cultivars.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.24 no.1
• /
• pp.1-10
• /
• 1979

In order to investigate the causes of epidemic out break of rice blast disease in 1978, investigations were undertaken in respect of climatic conditions, variety, cultural practice and plant pathology. During 1978, especially in August at heading time, it was higher temperature and humidity, higher frequency and amount of rainfall, lower amount of sunshine and solar radiation than less blast infested years. Nitrogen content in rice plant was higher than previous years. Acreage increase of semi-dwarf varieties brought about a result of proportional increase of new blast races which are able to infect the semi-dwarf varieties. It was concluded that those conditions mentioned above might have caused the result of severe neck blast disease in rice varieties in Korea, 1978.

• Journal of Climate Change Research
• /
• v.9 no.2
• /
• pp.133-142
• /
• 2018

Climate change will affect not only the crop productivity but also the pattern of rice disease epidemics in Korea. Impact assessments for the climate change are conducted using various climate change scenarios from many global climate models (GCM), such as a scenario from a best GCM or scenarios from multiple GCMs, or a combination of both. Here, we evaluated the feasibility of using a climate change scenario from the best GCM for the impact assessment on the potential epidemics of a rice leaf blast disease in Korea, in comparison to a multi?model ensemble (MME) scenario from multiple GCMs. For this, this study involves analyses of disease simulation using an epidemiological model, EPIRICE?LB, which was validated for Korean rice paddy fields. We then assessed likely changes in disease epidemics using the best GCM selected for individual agro?climatic zones and MME scenarios constructed by running 11 GCMs. As a result, the simulated incidence of leaf blast epidemics gradually decreased over the future periods both from the best GCM and MME. The results from this study emphasized that the best GCM selection approach resulted in comparable performance to the MME approach for the climate change impact assessment on rice leaf blast epidemic in Korea.

• Korean journal of applied entomology
• /
• v.11 no.1
• /
• pp.41-43
• /
• 1972

1. In order to investigate the epidemic outbreak of rice blast disease on the resistant variety Kwankon in 1969, this investigation was undertaken as a basis for breeding resistant varieties. 2. The 16 isolates collected from Kyunggi area were inoculated at the 3-4 leaf stage on 12 Japanese differential varieties used for identifying races under greenhouse conditions. Out of 16 isolates 15 were identified as C race group and one as N race group. Of the 15 rates, nine were C-8, two were C-7 and two were C-1. Of the remaining two isolates, one was similar to C-1, and the other was similar to C-5. 3. It is concluded that the epidemic in the resistant variety 'Kwanok' was due to the occurrence of the C race group, which can infect the Chinese type varieties.

• Research in Plant Disease
• /
• v.7 no.2
• /
• pp.86-92
• /
• 2001

This experiment was carried out to analyze the recent epidemic of rice blast in southern provinces of Korea in 1999 and 2000. Incidences of leaf blast and panicle blast in these years were 1.5 and 2.9 times greater than those in 1998, respectively. Cultivation areas of rice cultivars, Daesan, Ilmi and Dongan bred from Milyang 95 as a recurrent parent increased over the country from 11% in 1998 to 38.4% in 2000, which were grown in more than 85% of total paddy fields in Jeonnam province. Predominant race populations of Pyricularia grisea in the farmers' fields had been changed from KJ-301 to KI-1117 in 1999 and KI-1113 and KJ-105 in 2000. Distribution ratio of the KI-1117 race in 1998 in the southern provinces was 1.7%, but increased to 30% in 1999. Although the cultivars Daesan, Ilmi and Dongan have shown wide spectrum of resistance to many races including KJ-301, they were susceptible to such races as KI-1117, KI-1113 and, KJ-105. These three races could be further classified into two sub-races, KI-1117 and KI-1117a, KI-1113 and Kl-1113a, and KJ-105 and KJ-105a based on virulence to Daesan. The newly classfied races, Kl-1113a, Kl-1117a, and KJ-l05a were also pathogenic to Ilmi and Dongan. This indicates that rice blast epidemic in southern provinces in 1999 and 2000 resulted from the breakdown of the resistance of Daesan, Ilmi and Dongan by the rapid increase of virulent races KI-1117, KI-1113, KJ-105 and their new sub-races.

• Korean Journal of Agricultural Science
• /
• v.6 no.2
• /
• pp.97-104
• /
• 1979

The present study was attempted to find out the effects of different fertilizer levels on the process and pattern of blast epidemic of Milyang 23 which is a variety belong to Tongil-line of rice and very susceptible to new races of the blast fungus. The results obtained from the study are as follows. In general, the plant become more susceptible to blast with increase of fertilizers applied and there is a close relationship between the incidence of blast and levels of fertilizer. Such a relationship appears more clearly in case of the incidence of leaf blast while it is not so clear in case of the incidence of node blast and neck blast. In spite of low level of fertilizer, both of node and neck blast occur considerably and the difference compared with that of high level of fertilizer is not so great. Therefore, the disease escaping in the node or the neck of panicle by regulation of fertilizer level may be impossible. And also forecasting of the neck blast by estimate of the incidence of leaf blast is very difficult because of discontinuity of the incidence of blast on the leaf and the node.

• Korean Journal of Agricultural Science
• /
• v.12 no.2
• /
• pp.356-369
• /
• 1985

In Korea, inevitable researches for the blast control exactly started from 1927 by the organization of Office of Rural Development with the local extensive outbreak of panicle blast at Jeonlla Buk-Do Province in 1926. At present, the rice blast is still one of the most destructive and widespread diseases in spite of considerable contributions by rice scientists, particularly plant pathologists during last 55 years in Korea. Rice blast control and management are very difficult because of the marked variability in pathogenicity of the blast fungus. From the results obtained through the disease surveys during last 70 years, different 3 prevalence type of blast such as bimodal leaf-blast type, bimodal panicle-blast type and bimodal continual blast type were recognized. In generally speaking, pattern of blast outbreak is said to be characterized by severe outbreak of panicle blast after slight outbreak of leaf blast with discontinuity between leaf and panicle blast. So we have to pay much attention for successful management of panicle blast giving direct influence to rice yield. Main factors induce blast epidemic were pointed out to be breakdown of the disease resistance, nutritional unbalance such as excess application of nitrogen, delay of transplantation and longspell of rain fall by extensive surveys and researches on blast during last 70 years in Korea. The fact some of Japonica varieties such as Kokuryomiyako, Tamanishiki, Ginbozu and Pungok belong to varietal group A had been cultivated with extensive acrage over 30 years in this country should be mentioned by Korean rice scientists. Differences in field resistance between varieties in the same group are detectable and apparently small but sometimes epidemiologically significant differential effects may be found out in case of blast. Much more attention should be payed to accumulate the knowledges on field resistance for successful management of blast. Excess application of nitrogen is more effective to outbreak of panicle blast than that of leaf blast of IR varieties. In comparatively low level application of nitrogen infection rate of panicle blast of IR varieties is considerably high. Low temperature effects on outbreak of blast is very great. It results in remarkable increase of the inoculum potential on the leaf lesions and infection of panicle blast in leaf sheathes of IR varieties during the booting stage. In economic point of view, it is concluded that 5 times sprays of effective fungicides including 3 times before and 2 times after heading is good enough to control blast. We have experienced no one of control measures for blast is superior to all others. The integrated control measures was established as guideline of blast control around 1950 in Korea. This guideline must be helpful for rice growers as long as rice growing continue.

• Research in Plant Disease
• /
• v.8 no.4
• /
• pp.199-206
• /
• 2002

It was investigated on the relationship of the rice blast epidemics and the real-time meteorological factors, at the experimental paddy field in 1997. Weather factors(temperature, relative humidity, irradiation, precipitation, the direction of wind, wind speed, soil temperature and leaf-wetness, etc) were measured by using the automated weather station. The most influenced weather factor to blast epidemics, was the average max-temp($R^2$= 0.95) during 10 days before leaf blast epidemics, while the least thing was wind speed($R^2$= 0.24). The most potential weather factors correlated with the blast epidemics were T-ave(average temperature), T-max(maximum temperature), RH(Relative Humidity) and RD(Relative Humidity > 90% hrs). A statistics model(the regression equation) of the blast epidemics with the potential weather factors, was established as tallows ; Y = -3410.91 - 23.91 $\times$ T-ave ＋ 28.56 $\times$ T-max ＋ 41.0 $\times$ RH - 3.75 $\times$ RD, ($R^2$= 0.99). (T-ave >= 19$^{\circ}C$, T-max - T-ave >= 5.2$^{\circ}C$ and RH% >= 90.4%). According to the fitness test($\chi$$^2$) of the model, the observed blast disease severity was quite close to those expected.

• Research in Plant Disease
• /
• v.10 no.1
• /
• pp.1-7
• /
• 2004

The year of 2003 was characterized as a cool humid year. Low temperature and frequent rains were continued during March to July, resulting in 1.6 times higher rainfalls and 32％ less sunshine period compared to the average yean Due to 2003's climatic condition, rice blast, and bacterial leaf blight occurred severely. Higher rainfalls caused severe epidemic of phytophthora disease and, in case of red-pepper, 55％ of cultivation acreage was devastated by the disease over the country. Besides, crop diseases which become severe under cool-humid conditions, such as gray mold, sclerotinia rot, downy mildew, increased significantly compared to the previous year. In fruit trees, brown spot of apple, and pear scab occurred severely causing much yield loss.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.27 no.3
• /
• pp.183-192
• /
• 1982

The variability of rice productivity during last 2 decades (1961-1980) of ten years before and after the introduction of"Tongil" was reviewed from the epochal, regional and varietal points of view. During that period the cultivated area of paddy rice have remained almost unchanged, while the total rice production have got elevated from 3, 463 million metric tons in 1961 to 6.006 million metric tons in 1977, recording 73.4% increase. This remarkable increase in rice production is considered to be attributable much to the development and release of new high yielding variety, "Tongil", coupled with the amelioration of cultural techniques. However, in 1978 Tongil type varieties experienced the epidemic outbreak of blast disease due to the shifted race population of blast fungus and in 1980 recorded poor rice production as low as in 1960's due to the unfavorable weather stress throughout the rice growing season, giving rise to many problems awaiting solutions for securing the stabilized high production of rice. The rice yield has continued the gradual increase during last two decades but its difference between farmer and research organization have got wider from 79kg/10a during 1960 to 1971 to 101kg/l0a during 1972 to 1980, and also the inter-regional differences have been increased from 50-60kg/10a to 80kg/10a during those periods. Therefore, this proves that we have raised the upper boundary of rice yield by increasing the yield potential of rice variety but have not changed those absolute deviations. Estimates indicate that the increased rice production during that period was indebted 40 percent to the varietal improvement and 13 percent to the ameliorated agro-technologies, and the rest, 47 percent, could be ascribed to the other factors besides varieties and cultural technologies such as the improved agricultural environments, etc. Of course, even though it cannot be expected to unify the cultural environments and the cultural technologies, provided that much efforts are to be endeavored to minimize the yield difference of 20 percent between farmer and research organizations and the inter-regional yield difference of 20 percent, much increased rice production can be expected to be achieved with the current level of cultural technology and the yielding potential of the present rice varieties. In order to expedite the above effects on rice production the followings are to be put into practices consitently and steadfastly. 1. Reinforcement of breeding for varieties with high yielding potential and less susceptible to climatic-stress and pests, and of basic physicoecological studies of rice plant for improving the cultural technologies. 2. Continuous endeavor to secure the stabilized cultural environments by improving the soil fertility and increasing the drainage and irrigation facilities. 3. Political back-up to encourage the farmers' incentives for production 4. Precise surveys for agricultural statistics to facilitate the long-term planninge long-term planning.