• Korean Journal of Weed Science
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• v.31 no.2
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• pp.192-198
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• 2011

This study was conducted to investigate the herbicidal activity against Scirpus planiculmis (SCPPL) which has been reported as resistant biotype on sulfonylurea (SU) herbicides at the west coast reclaimed area first and proliferated continuously at Hwasung and Pyeongtaek in Gyeonggi province, and some Chungnam province. In order to investigate resistance breakability against SCPPL, new rice herbicides containing tefuryltrione [p-hydrophenyl pyruvate dioxygenase (HPPD) inhibitor], pyrimisulfan and triafamone[actolactate synthethase (ALS) inhibitor] were tested. In both lab and field experiments, tefuryltrione GR, 4-HPPD inhibitor showed growth retardation with a bleaching on the young leaves of SCPPL at early time after treatment. However, it restored and regerminated with insufficient control effect. On the other hand, pyrimisulfan+mefenacet SC, triafamone+tefuryltrione GR, and ALS inhibitor showed excellent control effect on SU-resistant SCPPL with growth retardation and necrosis. In particular, pyrimisulfan+mefenacet SC showed excellent controlling effect on SU-resistant SCPPL in regional field experiments.

• 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.

• The Korean Journal of Pesticide Science
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• v.9 no.3
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• pp.250-261
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• 2005

This study was conducted to investigate the herbicidal response and effective control strategy of sulfonylurea(SU)-resistant Scirpus juncoides Roxb. occurred in the paddy fields of Korea. A biotype of Scirpus juncoides Roxb. resistant to SU was identified in the paddy fields treated with SU herbicide-based mixtures for seven consecutive years. The apparent SU resistance observed in Scirpus juncoides Roxb. was completely confirmed in greenhouse tests. The susceptible biotype was almost controlled at the recommended dose of all the tested, but the resistant biotype was survived 20 to 30% even at 10 times higher dose of each the recommended dose of SU herbicides. The $GR_{50}$ values of 4 SU herbicides for the resistant biotype were 53 to 88 times higher than those for the susceptible biotype. The acetolactate synthase(ALS) isolated from the resistant biotype against bensulfuron-methyl and pyrazosulfuron-ethyl was less sensitive than that of the susceptible biotype. The $I_{50}$ values of the resistant biotype against bensulfuron-methyl and pyrazosulfuron-ethyl were 498 and 126 times higher than those for the susceptible biotype. A rapid diagnosis for identifying resistance of Scirpus juncoides Roxb. was possible within at least 3 days after SU herbicides. Three herbicides having different mode of action from SU herbicide, carfentrazone-ethyl, pyrazolate and simetryne exhibited excellent controlling effects on the resistant biotype of Scirpus juncoides Roxb. till 3.5 leaf stage. Among the SU-based herbicides, pyriminobac-methyl+pyrazosulfuroil-ethyl+carfentrazone-ethyl GR and azimsulfuron+carfentrazone-ethyl+pyriminobac-methyl GR were very effective to control resistant biotype of Scirpus juncoides Roxb. without rice injury. The resistant biotype which were not controlled with SU herbicise-based herbicides survived from the fields were effectively controlled by bentazone SL.

• Korean Journal of Weed Science
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• v.31 no.2
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• pp.119-133
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• 2011

Sulfonylurea (SU)-resistant weeds include seven annual weeds such as Monochoria vaginalis, Scirpus juncoides and Cyperus difformis, etc., and three perennial weeds of Scirpus planiculmis, Sagittaria pigmaea and Eleocharis acicularis as of 2010 since identification Monochoria korsakowii in the reclaimed rice field in 1998. The Echinochloa oryzoides resistant to acetyl CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors has been confirmed in wet-direct seeding rice field of the southern province, Korea in 2009. In the beginning of occurrence of SU-resistant weeds the M. vaginalis, S. juncoides and C. difformis were rapidly and individually spreaded in different fields, however, theses resistant weeds have been occurring simultaneously in the same filed as time goes by. The resistant biotype by weed species demonstrated about 10- to 1,000-fold resistance, base on $GR_{50}$ (50% growth reduction) values of the SU herbicides tested. And the resistant biotype of E. oryzoides to cyhalofop-butyl, pyriminobac-methyl, and penoxsulam was about 14, 8, and 11 times more resistant than the susceptible biotype base on $GR_{50}$ values. In history of paddy herbicides in Korea, the introduction of SU herbicides including besulfuron-metyl and pyrazosulfuron-ethyl that control many troublesome weeds at low use rates and provide excellent crop safety gave farmers and many workers for herbicide business refreshing jolt. The products and applied area of SU-included herbicides have been rapidly increased, and have accounted for about 69% and 96%, respectively, in Korea. The top ten herbicides by applied area were composed of all SU-included herbicides by 2003. The concentrated and successive treatment of ACCase and ALS inhibitors for control of barnyardgrass in direct-seeded rice led up to the resistance of E. oryzoides. Also, SU-herbicides like pyrazosulfuron-ethyl and imazosulfuron which are effective to barnyardgrass can be bound up with the resistance of E. oryzoides. The ALS activity isolated from the resistant biotype of M. korsakowii to SU-herbicides tested was less sensitive than that of susceptible biotype. The concentration of herbicide required for 50% inhibition of ALS activity ($I_{50}$) of the SU-resistant M. korsakowii was 14- to 76-fold higher as compared to the susceptible biotype. No differences were observed in the rates of [$^{14}C$]bensulfuron uptake and translocation. ALS genes from M. vaginalis resistant and susceptible biotypes against SU-herbicides revealed a single amino acid substitution of proline (CCT), at 197th position based on the M. korsakowii ALS sequence numbering, to serin (TCT) in conserved domain A of the gene. Carfentrazone-ethyl and pyrazolate were used mainly to control SU-resistant M. vaginalis by 2006, the early period, in Korea. However, the alternative herbicides such as benzobicyclone, to be possible to control simultaneously the several resistant weeds, have been developing and using broadly because the several resistant weeds have been occurring simultaneously in the same filed. The top ten herbicides by applied area in Korea have been occupied by products of 3-way mixture type including herbicides with alternative mode of action for the herbicide resistant weeds. Mefenacet, fentrazamide and cafenstrole had excellent controlling effects on the ACCase and ALS inhibitors resistant when they were applied within 2 leaf stage.

• The Korean Journal of Pesticide Science
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• v.11 no.4
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• pp.269-275
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• 2007

Four sulfonylurea(SU)-resistant Monochoria vaginalis(M. vaginalis) accessions were tested for levels of resistance to four SU herbicides which have been widely using in paddy fields of Korea, based on whole plant response and sensitivity of the target enzyme, acetolactate synthase(ALS). The resistant Naju, Nonsan and Gimje accessions were not affected to the survival by treatment with recommended dose of all SU herbicides tested. The $GR_{50}$ values for the Naju, Nonsan and Gimje accessions were 8- to 33-fold, 8- to 30-fold and 7- to 32-fold higher to recommended doses of all SU herbicides tested than the susceptible Cheongdo accession, respectively. However, the $GR_{50}$ values for Kimhae accession displayed an intermediate response and was only 4-to 13-fold more resistant than the susceptible accession. The ALS $I_{50}$ values for the Naju, Nonsan and Gimje accessions were 25- to 66-fold, 9- to 26-fold and 10- to 24-fold higher to recommended doses of all SU herbicides tested than the susceptible Cheongdo accession, respectively. However, the $I_{50}$ value for Kimhae accession was 4- to 9-fold more resistant than the susceptible accession, as determined by $I_{50}$ values of ALS.

• 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.

• 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.

• The Korean Journal of Pesticide Science
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• v.8 no.1
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• pp.63-70
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• 2004

Sulfonylurea(SU)-resistant Monochoria korsakowii has resently been found in rice fields in Korea. A quick, practical and accurate test of confirming herbicide resistance is necessary to take timely management decision. This article describes a rapid reliable assay to detect SU-resistant biotype of Monochoria korsakowii. Up to now, the resistance to SU has been usually checked by application seedlings with herbicide. This application technique is time consuming and not practical. Therefore, we have developed efficient, rapid and practical diagnosis which allow easy detection of the SU-resistant Monochoria korsakowii by survival rate and regenerated plant length to herbicide application after cutting plants $0.5\sim1cm$ from the planted surface. This new rapid diagnosis can determine the SU resistance of the Monochoria korsakowii within 7 days at least. If the resistance of Monochoria korsakowii is identified by the rapid diagnosis, the selection of herbicide according to the stages of plants for the effective control is very important. The resistant biotype which treated with SU herbicide-based mixtures survived from the fields could effectively be controlled by soil application of butachlor+pyrazolate GR or by foliar application of the mixtures of bentazone SL and 2,4-D SL.

• Weed & Turfgrass Science
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• v.7 no.1
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• pp.15-21
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• 2018

Since sulfonylurea (SU) herbicide-resistant Monochoria korsakowii in Seosan reclaimed land in 1998 was reported first, herbicide-resistant weed species and their area of occurrence have been steadily increasing. In recent years, Sagittaria trifolia resistant to SU herbicides has been reported in Gimhae, Gyeongnam province. While collecting S. trifolia for constructing barcode database of major weeds we were suspicious by the continuous variation in the leave morphology of the species. In order to identify the S. trifolia from S. aginash we barcoded the species collected from domestic using ITS and compared the sequence variation with the ITS sequences of S. aginash downloaded from NCBI. As a result, it was found that the plants collected from the domestic did not have any variation among individuals although they showed wide morphological variation. On the other hand, interspecific variation between S. trifolia and S. aginash was 4.6%. Plants that are difficult to identify using morphological characters can be identified quickly and accurately using the barcode technique. Herbicide-resistant weeds may require different management practices depending on the species even in the same genus. Domestic herbicide-resistant weeds are steadily increasing. Therefore, accurate identification of these species must be preceded for effective weed control.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.248-253
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• 2013

This study was conducted to select alternative herbicides to control herbicide-resistant and - troublesome weeds in rice fields, Korea. The resistant Echinochloa oryzicola to ACCase inhibitor was tested by herbicides registered to control Echinochloa oryzicola. And the resistant and troublesome weeds to sulfonylurea (SU) herbicides, ALS inhibitors, were tested by widely using herbicides to control the resistant weeds in Korea. The oxadiazon, pyrazolate, pretilachlor and benzobicyclone+thiobencarb effectively controlled resistant Echinochloa oryzicola to ACCase and ALS inhibitors at 0.5 leaf stage of the, Herbicides containing mefenacet or fentrazamide controlled effectively by the 2 leaf stage. In controlling other SU resistant weeds including Sagittaria trifolia and Ludwigia prostrate, benzobicyclon and mesotrione performed well all tested weeds, and carfentrazone and pytazolate were effective to broadleaf weeds. Sagittaria trifolia and Ludwigia prostrate, which were suspected to be resistance to SU herbicides, were well controlled by carfentrazone and pytazolate.