• Weed & Turfgrass Science
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• v.2 no.2
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• pp.131-137
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• 2013

The study was carried out to obtain the basic information on distribution and occurrence of weeds including resistant weeds to sulfonylurea herbicides in paddy fields of Gyeongbuk province. In weed distribution on life cycle, annual weed was occupied by 91.8% and perennials were 8.2%, respectively. In morphological distribution of weeds, broad leaf weeds were 85.7%, sedges was 9.1%, and grass weed was 3.8%, respectively. Sulfonylurea-resistant weeds in paddy fields of twelve regions were widely occurred except for Yecheon region. The six sulfonylurea resistant biotypes occurred in paddy fields of Gyeongbuk province were Lindernia dubia, Eleocharis kuroguwai, Monochoria vaginalis and Ludwigia prostrata. It revealed that occurrence rate and area of sulfonylurea-resistant weeds were about 15.9 % and 22,420 ha in Gyeongbuk province.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.4
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• pp.328-334
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• 2002

A Lindernia dubia (L.) Pennell var. dubia accession from Jeonnam province, Korea was tested for resistance to sulfonylurea (SU) herbicides, imazosulfuron and pyrazosulfuron-ethyl in whole-plant response bioassay. The accession was confirmed resistant to both herbicides. The $GR_{50}$ (herbicide concentration that reduced shoot dry weight by 50%) values of resistant accession were 264 and 19 times higher to imazosulfuron and pyrazosulfuronethyl, respectively, than that of the standard susceptible accession. The surviving resistant L. dubia after pyrazosulfuron-ethyl + molinate application can be controlled by sequential applications of soil-applied herbicides, butachlor, dithiopyr, pyrazolate, and thiobencarb and foliar herbicides, bentazon. Sulfonylurea-based mixtures such as mixtures of azimsulfuron + anilofos, bensulfuron-methyl + oxadiazon, pyrazosulfuron-ethyl + fentrazamide, and pyrazosulfuron-ethyl + anilofos + carfentrazon can also be used to control the surviving resistant L. dubia. However, use of these mixtures should be restricted to a special need basis. Thus, we suggest that sequential applications of non-SU-based mixtures such as butachlor + pyrazolate and MCPB + molinate + simetryne be used to control the surviving resistant L. dubia after SU herbicide applications. Rice yield was reduced 24 % by resistant L. dubia that survived after the pyrazosulfuron-ethyl + molinate application compared with pyrazolate + butachlor in transplanted rice culture. In vitro ALS activity of the resistant biotype was 40 and 30 times more resistant to imazosulfuron and pyrazosulfuron-ethyl, respectively, than the susceptible biotype. Result of in vitro ALS assay that the resistance mechanism of L. dubia to SU herbicides may be due, in part, to an alteration in the target enzyme, ALS.

• Korean Journal of Weed Science
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• v.18 no.3
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• pp.268-279
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• 1998

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.4
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• pp.286-291
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• 2003

Monochoria vaginalis is one of the most troublesome resistant weeds in Korean rice culture. Thus, the objectives of this study were to evaluate the response of M. vaginalis resistant to sulfonylurea(SU) herbicides and to determine alternative herbicides for the control of resistant M. vaginalis in direct seeded and transplanted rice culture in Korea. In greenhouse studies, the resistant biotype was 31-, 38-, 3172-, and 7-fold more resistant to ben-sulfuron-methyl, cyclosulfamuron, imazosulfuron, and pyrazosulfuron-ethyl, respectively, than the susceptible biotype, indicating cross-resistance to the SU herbicides used in this study. Non-SU herbicides, butachlor, carfentrazone-ethyl, mefenacet, pretilachlor, pyrazolate, and thiobencarb, several SU herbicide-based mixtures, ethoxysulfuron plus fentrazamide, pyrazosulfuron-ethyl plus pyrazolate plus simetryn, and non-SU herbicide-based mixtures, pyrazolate plus butachlor, pyrazolate plus pretilachlor, simetryn plus molinate, carfentrazone-ethyl plus butachlor, and carfentrazone-ethyl plus thiobencarb can be used to control both the resistant and susceptible biotypes of M. vaginalis when applied before the second leaf stage. In the field experiment, the resistant biotype of M. vaginalis that survived from the paddy fields treated with a SU herbicide-based mixture could effectively be controlled by using mixtures of bentazone plus MCPA, bentazone plus mecoprop-P, and bentazone plus 2,4-D when applied at 2 or 4 main leaves. Our results suggest that the SU-resistant M. vaginalis had not developed multiple resistances to herbicides with different modes of action. In particular, bentazone plus MCPA and bentazone plus mecoprop-P were effective control measures after failure to control resistant M. vaginalis in Korean rice culture.

• Korean Journal of Agricultural Science
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• v.41 no.1
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• pp.17-22
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• 2014

This study was conducted to evaluate the efficacy of formulations and application timings of imazosulfuron+fentrazamide in rice field. Weeding efficacy of imazosulfuron+fentrazamide SC (75+300 g a.i./ha) was more than 95% except Bidens tripartita. The efficacy of this formulation was not related to its formulations but was highly related to application timing. Herbicide application before 5 days after transplanting was best timing to get a maximum weed control. Systemic application before and after transplanting was much higher than single application for weed control. Second leaf stage of Echinochloa spp. and sulfonylurea resistant Monochoria vaginalis was controled over 90% in the imazosulfuron+fentrazamide SC (75+300 g a.i./ha). Based on these data, imazosulfuron+fentrazamide can be applied to provide effective weed control especially in the field infested with herbicide resistant M. vaginalis.

• 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.

• Korean Journal of Weed Science
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• v.32 no.2
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• pp.133-138
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• 2012

This study was conducted to investigate the herbicidal activity against resistant biotype on sulfonylurea (SU) herbicides such as Scirpus juncoides and Monochoria vaginalis at the glasshouse and paddy rice cultivation area. In order to investigate resistance breakability against SU-resistanted annual weeds, new rice herbicides containing tefuryltrione [p-hydrophenyl pyruvate dioxygenase (HPPD) inhibitor] were tested. In both lab test and field experiment, tefuryltrione mixture, 4-HPPD inhibitor had shown excellent efficacy with a bleaching on the leaves of resistant annual weeds at early time after treatment and showed excellent persistance. Especially, tefuryltrione mixture had shown excellent controlling effect on annual and perennial SU-resistant S. juncoides in the regional field experiment. In phytotoxicity test, this tefuryltrione mixture had shown good selectivity to common rice species.

• Korean Journal of Weed Science
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• v.32 no.1
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• pp.57-69
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• 2012

This study was conducted to find the effective management of main weeds including herbicide-resistant Echinochloa oryzicola, Scirpus juncoides and Monochoria vaginalis in direct seeded rice on puddled paddy surface. The dominant dominances in direct seeded rice on puddled paddy surface were increased for three years between 2009-2011. In weed distribution in 2011, the occurrence density of S. juncoides decreased greatly, but it of E. oryzicola increased especially as compared with it of 2009. Benzobicyclon, mesotrione and pyrimisulfan were effective to sulfonylurea(SU)-resistant S. juncoides and M. vaginalis at 5 and 12 days after seeding, however, the efficacy of bromobutide to sulfonylurea-resistant M. vaginalis was decreased slightly at 12 days after seeding. And carfentrazon and pyrazolate were ineffective to S. juncoides. In direct seeded rice on puddled paddy surface which ACCase and ALS inhibitor-resistant E. oryzicola was not occurred, benzobicyclon+penoxsulam+pyrazosulfuron-ethyl ET, bromobutide+imazosulfuron+metamifop GR, and flucetosulfuron+mesotrione+pretilachlor GR showed the control effect over 94% to main weeds included sulfonylurea-resistant S. juncoides and M. vaginalis. The E. oryzicola dominating in direct seeded rice on puddled paddy surface were not any affected to the survival by treatment with recommended doses of cyhalofop-butyl and penoxsulam tested. The ACCase and ALS inhibitor-resistant E. oryzicola was effectively controlled by mefenacet and fentrazamide up to the 2nd leaf stage. In direct seeded rice on puddled paddy surface domiating coincidentally by herbicide-resistant E. oryzicola, S. juncoides and M. vaginalis, "one-shot herbicide" included with mefenacet, fentrazamide, penoxsulam and metamifop could't be used because of low control effect or rice injury. The sequential treatment of benzobicyclon+thiobencarb SE and bensulfuron+mefenacet+thiobencarb GR controlled effectively the herbicide-resistant E. oryzicola, S. juncoides and M. vaginalis in direct seeded rice on puddled paddy surface. The days required by the 3rd leaf stage of herbicide-resistant E. oryzicola, S. juncoides and M. vaginalis in direct seeded rice on puddled paddy surface seeded in May 20 shortened by 4 days as compared with it of June 10.

• Korean Journal of Weed Science
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• v.32 no.1
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• pp.52-56
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• 2012

The occurrence of sulfonylurea-resistant weeds has recently increased in Korea. A survey was performed to investigate major paddy field weeds and frequently used herbicides in Gangwon province, Korea in order to establish a system to efficiently control herbicide-resistant weeds. The dominant paddy field weeds included Monochoria vaginalis (14%), Sagittaria trifolia (14%), Scirpus juncoides (13%), and Echinochloa spp. (13%), and the most widely used herbicides were oxadiazon 12% EC (27%), butachlor 5% GR (20%), oxadiargyl 1.7% EC (16%), and benzobicyclon+imazosulfuron+pyriminobac-methyl 6.1% SC (14%) in Gangwon province, Korea. Many paddy rice growers considered Scirpus juncoides, S. trifolia, Echinochloa spp. and M. vaginalis as herbicide-resistant weeds. An extensive research deserves to be conducted to monitor occurrence of herbicide-resistant paddy weeds in Gangwon province, Korea.

• The Korean Journal of Pesticide Science
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• v.7 no.4
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• pp.239-247
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• 2003

This experiment was carried out to study the resistant mechanism of sulfonylurea(SU) herbicides to Monochoria korsakowii occurring in the rice fields of Korea. The activity of acetolactate synthase(ALS), absorption and translocation of $[^{14C}]$bensulfuron-methyl, and DNA sequence of ALS genes were studied. The apparent SU resiatance to Monochoria korsakowii was confirmed in greenhouse testes. Fresh weight accumulation$(GR_{50})$ in the resistant biotype was about 5- to 64-fold higher in the presence of six SU herbicides compared to the susceptible biotype. The ALS activity isolated from the resistant biotype to herbicides tested was less sensitive than that of susceptible biotype. The concentration of herbicide required for 50% inhibition of ALS activity$(I_{50})$ was 14- to 76-fold higher as compared to the susceptible biotype. No differences were observed in the rates of $[^{14C}]$bensulfuron uptake and translocation. However, the DNA sequence from the resistant biotype differed from that of the susceptible biotype by single nucleotide substitution at three amino acid each in the middle region excluding the ends of ALS genes. We found three point mutations causing substitution of serine for threonine at amino acid 168, arginine for histidine at amino acid 189, and a aspartic acid for phenylalanine at amino acid 247, respectively, in the resistant biotype.