• Korean Journal of Weed Science
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• v.14 no.4
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• pp.258-264
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• 1994

The weed survey in lowland rice field in 1992 was conducted to identify weed population change as affected by different elevation, soil type and cultivation pattern at Gangweon province. There were more perennial weeds in plain and east coastal area while more annual weeds in mid alpine and alpine area. Meanwhile, perennial weed species was more dominant at ordinary and sandy soil but annual weed species was more dominant at poorly drained soil. In general, hand and machine(30 day old seedling) transplanting would result in higher dominant weed species of perennial while there was more annual weed species in machine (10 day old seedling) transplanting and dry seeding, respectively. Also, annual weed species was more predominant at spring plowing time compared to autumn plowing time. Particularly, there was change in dominant weed species with time. In 1971 annual weed species was more predominant but perennial weed species was highly dominant in 1981 and 1992.

• Weed & Turfgrass Science
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• v.3 no.2
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• pp.78-85
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• 2014

The survey of weed occurrence was conducted to identify dominant weed species in the paddy field. Total 346 sites of the 12 regions in Chungbuk Province in Korea were investigated in July, 2013. Weed flora was composed of 43 species belonged to 15 families. The compositions of major plant families, Cyperaces, Poaceae, Pontederiaceae and Asteraceae, were 21.5, 17.4, 15.5 and 12.7%, respectively. Based on life cycle, weed species was grouped into annuals of 71.3 and perennials of 28.1%. The most dominant weed species in paddy fields of Chungbuk Province were Monochoria vaginalis (14.5%), followed by Scirpus juncoides (10.5%), Echinochloa oryzoides (9.3%), Eleocharis kuroguwai (7.0%), Aeschynomene indica (6.2%) et al. The similarity of paddy weeds in 12 regions observed through TWINSPAN analysis was distinguished by Persicaria longiseta, Aneilema keisak, Persicaria thunbergii, Fimbristylis millacea, Blyxa japonica, Digitaria ciliaris, Potamogeton distinctus, Cyperus nipponicus. This information could be useful for estimation of future weed occurrence and establishment of weed control methods in chungbuk province in Korea.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.413-420
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• 2013

The climate change affects the growth and development of weeds as well as the outbreak of weeds. Especially, the occurrences of problematic paddy weeds due to climate change might cause the difficulties in weed control. This study therefore, investigated the current dominance and distribution of paddy weeds. As a result of the study on paddy weeds in northern Gyeonggi-do, there were total of 65 taxonomy groups including 23 family, 41 genus, 57 species, 7 subspecies and 1 variety. Among all the plants, 46 species were annual plants and 16 were perennial plants. Echinochloa crus-galli was the highest in importance analysis and the followings were in order of Ludwigia prostrate and Lemna paucicostata. The similarity of different paddy weeds in different regions observed through TWINSPAN analysis was distinguished by Fimbristylis miliacea, Rotala indica and Cyperus flaccidus. Regional differences shown in CCA analysis using weed species and soil environment revealed that Gimpo-si and Namyangju-si has difference soil and weeds, which are features that distinguished them from other regions. In northern Gyeonggi-do the result of paddy weed research showed the interregional difference not in dominant weeds but in distribution species.

• Korean Journal of Weed Science
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• v.18 no.4
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• pp.356-363
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• 1998

In general weed vegetation analysis has been applied to the study of weed population shift. However, it is a limited tool for understanding a problem region and a specific weed species in a certain area. Recently GIS may be used as an important tool to solve this target or to conduct specific field analysis which enables to introduce a reasonable management strategy. Thus, the GIS study was carried out to understand an integrated weed population changes between 1981 and 1992 in Korea. The nationwide weed survey was performed through the whole rice paddy fields in 1981 and 1992. Weed occurrence was totally different over whole country based on these data. In 1981 a region with high weed occurrence was at western and central areas of Korea in terms of weed population density but this was changed into western and southern area in 1992. In both years there were high weed population density at Taean, Seosan county of Chungnam province in Korea. Thus, this particular area may be needed to introduce a special strategy to reduce weed population density and/or to control problem weed species.

• Korean Journal of Weed Science
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• v.18 no.4
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• pp.364-370
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• 1998

A weed population has been mainly analyzed through vegetative analysis method in ecology. However, this method is difficult to understand a detailed feature of weed dominance in terms of region and a particular weed species. Since GIS(Geographic Information System) tool has been introduced, this constraint was able to be solved. GIS analysis for the nationwide weed survey data in 1981 revealed that most predominant weed was Monochoria vaginalis and this species predominated mostly in a western part of Chungnam, a part of Kyunggi, a northern and southern part of Kyungbuk province of Korea. Eleocharis kuroguwai which was the most predominant weed species in 1992 was occurred at southern part of Kyunggi, central and western parts of Chungnam, and southern western part of Chumnam at the GIS analysis. GIS analysis was proven to give much more detailed information than vegetative analysis of weed population and this means that a data analysis by GIS would be used for operating a high effective control strategy against target weed species and site.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.341-347
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• 2013

The survey of weed occurrence was conducted to identify problematic weed species on the paddy field. Total 524 sites of the 17 regions in Chungnam Province in Korea were investigated from June to August, 2013. In the whole region, 23 weed species were identified including 19 annuals and 4 perennials. The most dominant weed species in Chungnam paddy fields were Echinochloa crus-galli (25.3%), followed by Monochoria vaginalis (11.9%), Eleocharis kuroguwai (10.3%), Bidens tripartite (9.3%) and Aneilema japonicum (8.5%). The 95.2% of the investigation sites was determined under dominance value 1 (range of cover <10: numerous individuals) by Braun-Branquet indicating proper weed control in the paddy fields. This information could be useful for estimation of future weed occurrence, weed population dynamics and establishment of weed control methods in Chungnam Province in Korea.

• Agrochemical news magazine
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• v.25 no.3 s.196
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• pp.18-21
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• 2004

• The Korean Journal of Pesticide Science
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• v.12 no.1
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• pp.1-8
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• 2008

The widespread and diverse sulfonylurea (SU) resistance problem has found in Korea, where one-shot-treatment herbicides such as pylazosulfuron/molinate and bensulfuron/molinate have been used continuously since 1989. The SU-resistant weeds of 7 annual weeds and 3 perennial weeds as of 2008 have confirmed in paddy fields in Korea. An effective management to SU-resistant weeds requires an integrated approach toward the weed control system, in particular, as to the drastic changes of herbicides development. Recent trend of new paddy herbicides in Japan has been developing to maximize the management of SU-resistant weeds. In the future, it is expected that the development of paddy herbicides in Korea is likely to be shifted toward the new "one-shot-treatment" included with herbicides of over 3-ways to maximize the control of resistant weeds. Bromobutide and carfentrazone are effective against sedges and broad-leaved weeds, respectively, and benzobicyclone and pyrimisulfam are effective against sedges and broad-leaved weeds.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.312-317
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• 2014

This study was conducted to obtain basis information for effective weed control by the fact-finding survey of herbicides use at farmer's level and distribution of herbicide resistant weeds in paddy field of Jeonbuk province, Korea. The distributions of major paddy field weeds and frequently used herbicide according to the survey were as follows. The dominant weeds in rice paddy field were Echinochloa crus-galli, Eleocharis kuroguwai, Scirpus juncoides, Monochoria vaginalis, etc.. Preferred herbicides widely used by farmers were ranked in the following order, early and middle treatment (48.0%), treatment before transplanting (36.7%) and foliar treatment (15.3%). The occurrence of herbicide-resistant weeds according to collected paddy soils was as follows. The occurring area of herbicide-resistant weeds was 24,413 ha, approximately 18.4% of rice cultivation area. Herbicide-resistant weeds were occurred in four species. The order of occurrence were Scirpus juncoides (39.0%) > Monochoria vaginalis (27.8%) > Echinochloa crus-galli (16.6%) and Cyperus difformis (16.6%). This information could be useful for estimation of future herbicide-resistant weed and establishment of herbicide-resistant weed control methods in Jeonbuk province, Korea.

• Weed & Turfgrass Science
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• v.7 no.1
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• pp.46-53
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• 2018

This study was conducted to establish standard fresh weight data about the minimum amount of occurred weeds at untreated paddy fields, upland fields and orchard fields (including non-cultivated land) in 10 areas. The amount of occurred weeds in each area was compared fresh weight with dry weight. The average percentage for ratio of dry weight to fresh weight in paddy fields was concluded to be 14.8% of Echinochola crus-galli, 12.5% of annual weeds (including Echinochola crus-galli), and 13.9% of perennial weeds. The average percentage for ratio of dry weight to fresh weight in upland fields was concluded to be 20.1% of annual weeds and in orchard fields was concluded to be 18.4% of annual and perennial weeds. According to the research, standard fresh weight about the minimum amount of occurred weeds at untreated paddy fields was proposed to $210g\;m^{-2}$ of Echinochola crus-galli, $400g\;m^{-2}$ of annual weeds (including Echinochola crus-galli), and $220g\;m^{-2}$ of perennial weeds. Standard fresh weight about the minimum amount of occurred weeds at untreated upland fields was proposed to $250g\;m^{-2}$ of annual weeds and at untreated orchard fields was proposed to $550g\;m^{-2}$ of annual and perennial weeds.