• Korean Journal of Agricultural Science
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• v.42 no.2
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• pp.87-92
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• 2015

This study was conducted to evaluate the herbicidal efficacy of carfentrazone-ethyl mixtures in direct-seeding flooded rice. The efficacy of three different carfentrazone-ethly mixtures was greater than pyrazosulfuron-ethyl pyriminobac-methyl GR (PP GR). Weeding efficacy of three different carfentrazone-ethly mixtures was more than 96.9%. No phytotoxic effect was observed in the rice based on the plant height and the number of tillers. Yield of rice un three different carfentrazone-ethly mixtures application was more than both in the PP GR and in the hand weeding. Based on these data, three different carfentrazone-ethly mixtures can be applied to provide an effective weed management in direct-seeding flooded rice.

• Korean Journal of Agricultural Science
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• v.41 no.2
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• pp.85-99
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• 2014

Sulfonylurea (SU)-resistant weeds of eight annual weeds, Monochoria vaginalis, Scirpus juncoides and Cyperus difformis, etc., and four perennial weeds, Scirpus planiculmis, Sagittaria pigmaea, Eleocharis acicularis and Sagittaria trifolia as of 2013 since identification Monochoria korsakowii in the reclaimed rice field in 1998. And the resistant Echinochloa oryzoides to ACCase and ALS inhibitors has been confirmed in rice fields of the southern province, Korea in 2009. In the beginning, the M. vaginalis, S. juncoides and C. difformis of these SU-resistant weeds were rapidly and individually spreaded in different fields, however, these resistant weeds have been occurring simultaneously in the same filed recently. The resistant biotype by weed species demonstrated about 10-to 1,000-fold resistance, based on $GR_{50}$ 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. The products and applied area of SU-included herbicides have been increased rapidly, and have accounted for about 69% and 96% in Korea, respectively. In Korea, the main cause of SU-resistant weed is extensive use of these herbicides. 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 rice led up to the resistance of E. oryzoides. Also, SU-herbicides like pyrazosulfuron-ethyl and imazosulfuron which 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. Acetolactate synthase (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 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 fieled. 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 2nd leaf stage.

• Korean Journal of Environmental Agriculture
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• v.13 no.3
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• pp.279-287
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• 1994

To develop mixed pesticides of herbicide and topdressing fertilizer for paddy rice, twelve mixtures were formulated with combination of urea coated with different level of acrylic acid wax(AAW) and four herbicides, which were thiobencarb, pretilachlor, mefenacet + bensulfuron-methyl and mefenacet + bensulfuron-methyl + dymron, and effects of the mixtures for weed control, phytotoxicity and rice tillering were investigated in the laboratory and the field experiments. Release rates of active ingredient of herbicides in the distilled water were over 90% during 24 hours same as that of the reference herbicides. The release rates of nitrogen showed different patterns according to coated level of granular urea with acrylic acid wax. Optimum release rate of nitrogen as $NH_4-N$ was obtained by 5.5% AAW coating on urea for thiobencarb or pretilachlor mixture, and by 4.0% AAW coating on urea for mefenacet + bensulfuron-methyl or mefenacet + bensulfuron-methyl + dymron mixture. The pesticide active ingredients of the mixtures were stable, which showed $3.7{\sim}8.0%$ of degradation rate after 90 days of storage under $50^{\circ}C$. Effects on weed control of mixtures were acceptable for both annual and perennial weeds, while ACRI-M9213 mixture showed considerable phytotoxicity at double dose of standard. When treated the mixed pesticides to paddy rice, rice growth status including culm length, ear length, panicle number and polished rice yield exhibited no significant differences compared with the conventional treatment.

• Environmental Mutagens and Carcinogens
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• v.24 no.1
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• pp.33-39
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• 2004

To validate and to estimate the chemical hazard playa very important role to environment and human health. The detection of many synthetic chemicals including agrochemicals that may pose a genetic hazard in our environment is of great concern at present. Since these substances are not limited to the original products, and enter the environment, they have become widespread environmental pollutants, thus leading to a variety of chemicals that possibly threaten the public health. Pyrazosulfuron-ethyl [Ethyl-5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate, $C_{14}H_{18}N{6}O_{7}S,$ M.W. =414.39, CAS No. 93697-74-6], is one of well known rice herbicide belong in the sulfonyl urea group. To clarify the genotoxicity of this agrochemical, Ames bacterial reversion assay, in vitro chromosomal aberration assay with Chinese hamster lung (CHL) fibroblast and bone marrow micronucleus assay in mice were subjected. In Ames assay, although pyrazosulfuron-ethyl revealed cytotoxic at 5,000-140 $\mug/plate$ in Salmonella typhimurium TA100, no dose-dependent mutagenic potential in 4.4～70 $\mug/plate$ of S. typhimurium TA 98, TA 100, TA1535 and TA 1537 both in the absence and presence of S-9 metabolic activation system was observed. Using CHL fibroblasts, the 50% cell growth inhibition concentration $(IC_{50})$ of pyrazosulfuron-ethyl was determined as 1,243 $\mug/mL,$ and no chromosomal aberration was observed both in the absence and presence of S-9 mixture in the concentration range of 311-1,243 $\mug/mL.$ And also, in vivo micronucleus assay using mouse bone marrow, pyrazosulfuron-ethyl revealed no remarkable induction of MNPCE (micronucleated polychromatic erythrocytes/1000 polychromatic erythrocytes) in the dose range of 625-2,500 mg/kg body weight when administered orally. Consequently, Ames bacterial gene mutation with Salmonella typhimurium, in vitro chromosome aberration with mammalian cells and in vivo bone marrow micronucleus assay revealed no clastogenic potential of pyrazosulfuron-ethyl in this study.

• The Korean Journal of Pesticide Science
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• v.8 no.1
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• pp.22-29
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• 2004

To evaluate mutagenicity of Phosphinotricin Acetyltransferase(PAT) which is expressed by the glufosinate-resistance gene pat, in vitro reverse mutation test using Salmonella typhimurium, chromosome aberration test using chinese hamster lung(CHL) cells and in vivo micronucleus test of mice were performed. In the reverse mutation, the PAT did not induce mutagenicity in Salmonella typhimurium TA 98, TA 100, TA 1535, TA 1537 with and without metabolic activation at $5000{\mu}g/plate$. In the chromosome aberration test, the results showed no incidence of increased structural and numerical chromosome aberrations at any doses tested(100, 10, $1{\mu}g/mL$). In micronucleus test, the ratio of micronuclei was measured in polychromatic erythrocytes of bone marrow of male ICR mice intraperitoneally administrated with PAT(1250, 625, and 313 mg/kg), the results showed no incidence of increased micronucleated polychromatic erythrocytes (MNPCE). These results indicate that PAT might not have mutagenic potential in vitro and vivo systems.

• Korean Journal of Weed Science
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• v.5 no.2
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• pp.155-163
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• 1985

Three pyrazole-herbicides, pyrazolate, pyrazoxyfene and benzophenap, were evaluated for their interaction in controlling barnyardgrass (Echinochloa crusgalli) with two chloroacetamide-herbicides, butachlor and pretilachlor. Percent inhibition of barnyardgrass growth by pyrazolate, pyrazoxyfene, and benzophenap was 44%, 64%, and 0%, respectively, when each was applied at the 1.5 leaf-stage of barnyardgrass at a rate of 3㎏ ai per ㏊ as single treatment, and the benzophenap showed 60% inhibition when it was applied at the coleoptile stage. While the lowest rate controlling the 1.5 leaf-stage barnyardgrasses by 98 to 100% of the butachlor and pretilachlor was 1.5㎏ and 200g per ㏊, respectively. All of the combinations of pyrazolate with butachlor, pyrazoxyfene with pretilachlor, and benzophenap with butachlor have shown synergistic interaction in controlling barnyardgrass on the Chisaka's isobole of 90% growth inhibition as well as on the Colby`s interaction efficacy data; synergism indices were 2.44, 1.62 and 1.52 in order. The dose combinations shown the maximal synergism were 1870g of pyrazolate with 140g of butachlor (1:0.075), 33008 of pyrazoxyfene with 338 of pretilachlor (1:0.01), and 3350g of benzophenap with 520g of butachlor (1:0.15) on the ai/㏊ basis.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.236-241
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• 2013

Introduction of rye living mulch in soybean production is important for labor-saving and reduction of herbicide usage for weeding by weed suppression and for soil conservation by mulching of rye. Soybean and rye were row-planted and broadcasted simultaneously at different planting times (May 15, May 25, June 5) and row widths (35 and 70 cm) in 2010, different soybean cultivars (Daepoong, Singi) and planting times (May 15 and June 1) in 2011, respectively, and investigated weed occurrence, early growth and yield of soybean. Acalypha australis, which is known to herbicide-resistant weed, could be controlled ecologically by rye living mulch. Occurrence of Acalypha australis was controlled effectively also by mixture of alachlor and linulon at no mulch in 2011. Early growth amount of soybean plant per area was increased by narrow row width (35 cm) at rye living mulch, which was helpful in the control of weeds, but grain yield of soybean with narrow row was decreased compared to conventional row width (70 cm) at the planting in early June. It is concluded that soybean planting as row width 70 cm in early June is proper at simultaneous planting with rye.

• Molecular & Cellular Toxicology
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• v.2 no.3
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• pp.176-184
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• 2006

The controversy on genotoxicity of molinate, an herbicide, has been reported in bacterial system, and in vitro and in vivo mammalian systems. To clarify the genotoxicity of molinate, we performed bacterial gene mutation test, in vitro chromosome aberration and mouse lymphoma $tk^{+/-}$ gene assay, and in vivo micronucleus assay using bone marrow cells and peripheral reticulocytes of mice. In bacterial gene mutation assay, no mutagenicity of molinate ($12-185{\mu}g/plate$) was observed in Salmonella typhimurium TA 98, 100, 1535 and 1537 both in the absence and in the presence of S-9 metabolic activation system. The clastogenicity of molinate was observed in the presence ($102.1-408.2\;{\mu}g/mL$) of metabolic activation system in mammalian cell system using Chinese hamster lung fibroblast. However, no clastogenicity was observed in the absence ($13.6-54.3\;{\mu}g/mL$) of metabolic activation system. It is suggested that the genotoxicity of molinate was derived some metabolites by metabolic activation. Molinate was also subjected to mouse lymphoma L5178Y $tk^{+/-}$ cells using microtiter cloning technique. In the absence of S-9 mixture, mutation frequencies (MFs) were revealed $1.4-1.9{\times}10^{-4}$ with no statistical significance. However, MFs in the presence of metabolic activation system revealed $3.2-3.4{\times}10^{-4}$ with statistical significance (p<0.05). In vivo micronucleus (MN) assay using mouse bone marrow cells, molinate revealed genotoxic potential in the dose ranges of 100-398 mg/kg of molinate when administered orally. Molinate also subjected to acridine orange MN assay with mouse peripheral reticulocytes. The frequency of micronucleated reticulocytes (MNRETs) induced 48 hr after i.p. injection at a single dose of 91, 182 and 363 mg/kg of molinate was dose-dependently increased as $10.2{\pm}4.7,\;14.6{\pm}3.9\;and\;28.6{\pm}6.3\;(mean{\pm}SD\;of\;MNRETs/2,000\;reticulocytes)$ with statistical significance (p<0.05), respectively. Consequently, genotoxic potential of molinate was observed in in vitro mammalian mutagenicity systems only in the presence of metabolic activation system and in vivo MN assay using both bone marrow cells and peripheral reticulocytes in the dose ranges used in this experiment. These results suggest that metabolic activation plays a critical role to express the genotoxicity of molinate in in vitro and in vivo mammalian system.

• Korean Journal of Weed Science
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• v.31 no.4
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• pp.384-393
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• 2011

Sulfonylurea herbicide-resistant weeds are spreading widely and distributed about 106,951 hectare in paddy rice fields in Korea. Morever all biotype of Scirpus juncoides which were collected at 69 spots all over paddy rice fields in 2008 were identified biotype of sulfonylurea herbicide-resistant. Benzobicyclon is a p-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor, which is absorbed through root and basal stem of weeds so cause bleaching of newly developing leaves. Benzobicyclon was very effective to control Scirpus juncoides, Monochoria vaginalis, sedges and broadleaves weeds, so it have been developed various formulation like a suspension concentrate (SC), a water dispersible granule (WG), a granule (GR) and a DT (tablet for Direct application). During recently 6 years, benzobicyclon-mixtures herbicides have been registered over than 54 products in paddy fields. Herbicidal efficacy by formulations of benzobicyclon and its mixture herbicides were highest in DT, followed by SC and GR. Herbicidal efficacy of the kaolin and $CaCO_3$ carrier of GR was better and stable than that of talc and bentonite carrier. Growth and yield of rice were not affected much by formulations, application rates and rice cultivation methods.

• 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.