• Journal of Environmental Science International
• /
• v.14 no.4
• /
• pp.445-449
• /
• 2005

A simple and sensitive analytical method based on RP-HPLC with UV detector$(225{\cal}nm)$ and mobile phases using $0.1{\%}$ phosphoric acid and acetonitrile was developed for simultaneous determination of quinclorac, bentazone, 2,4-D, bensulfuron-methyl, dymuron, capropamide, pencycuron, ethofenprox. This method was resulted in recovery of $78{\~}96{\%}$ with RSD $3.3{\~}7.5{\%}$, LODs $0.12{\~}0.84$ and LOQs $0.34{\~}1.20{\cal}mg/L$. Calibration curves were linear with r of $0.9995{\~}0.9999$.

• Korean Journal of Weed Science
• /
• v.12 no.3
• /
• pp.271-291
• /
• 1992

This study was conducted to survey the situation of direct rice seeding in Honam province in Korea to investigate problems and seek countermeasure of weed control in direct rice seeding. The total area of direct rice seeding in the south-western part of Korea (Chonbuk, Chonnam, and Chungnam) was 1650.8ha (732.1ha for direct seeding in dry field and 918.7ha for direct seeding in flooding field) in 1992. The followings are summary of the study. 1. In case of direct rice seeding in dry field, butachlor EC and G at 3 to 5 DAS was mostly selected by farmers to control weeds in dry field. Benthiocarb or chlornitrofen was also used in few cases. At 10 to 14 DAS just before rice emergence, tank misture of butachlor EC and paraquat was treated by some farmers. At 35 to 40 days, after flooding mixture of sulfonylurea derivatives was sequentially applied. Surviving weeds including barnyardgrass were finally controlled by mixture of bentazon+quinclorac WP foliage application. 2. In case of direct rice seeding in flooding field, weed control were mostly unsuccessful partially due to wrong selection of herbicide and missing the optimum application time. Three relatively successful weed control in the survey were summarized as follows. 1) Oxadiazon EC, butachlor or benthiocarb were treated just after puddling(5 to 7 days before seeding). then mixture of bentazone+quinclorac WP or sulfonylurea derivatives was sequently applied to control remaining weeds at 20 days after seeding. 2) Mixtures of bensulfuronmethyl+dimepiperate G, pyrazosulfuronethyl+molinate G, or bensulfuronmethyl+mefenacet+dymron G were applied at 11 days after puddling when barnyardgrass were at 2.0 leaf stage. Phytotoxicity was not found in case of mixture of bensulfuronmethyl+dimepiperate G but found in the other two cases but disappeared later. 3) Mixtures of bensulfuronmethyl+quinclorac G., pyrazosulfuronethyl+quinclorac G or betazone and quinclorac G were treated after 18 to 20 days after puddling when barnyardgrass was within 3.0 leaf stage. It showed good weed control in both annuals and perrenials without phytotoxicity. On the contrary, other sulfonylurea derivatives such as middle periodic herbicide showed poor weed control against barnyardgrass, so that sequential treatment of bentazone+quinclorac WP mixture was required. 3. Herbicidal characteristics and optimum application time of 45 rigistered herbicides in Korea were analyzed to discover new substitute for quinclorac mixture, that showed excellent weed control against barnyardgrass at its 3 leaf stage or older. The analysis revealed that 70% of herbicides were for preemergence and the others were post periodic herbicide. Most farmers favor to apply herbicide when rice seedlings completely rooted, at this time barnyardgrass are at 2.5-3.0 leaf stage. Therefore herbicide of which optimum application time had long is required. In this study. 6 middle periodic herbicides among sulfonylurea derivatives and 2 quinclorac mixture were selected and evaluated their weeding spectrums at different leaf stage of barnyardgrass in both soil application in flooding condition and foliage application in dry paddy field. The order of weeding spectrum in magnitude was as follows : bentazone+quinclorac WP> bentazone + quinclorac G>bensulfuronmethyl + quinclorac G>pyrazosulfuronethyl + quinclorac G> pyrazosulfuronethyl + Molinate G>bensulfuronmethyl + mefenacet + dymron G>bensulfuronmethyl + mefenacet G>bensulfuron methyl+benthiocarb G. The above results coincided with that of the survey. In conclusion, there is no proper substitute for quinclorac mixrure, which can control barnyardgrass at 3.0 leaf stage or even older. Therefore quinclorac should be supplied continuously to farmers in order to anchor direct rice seeding in Korea. Author suggested the followings to eastablish direct rice seeding technology effectively and quickly : 1) A tentatively named "The research committee for direct rice seeding" which was composed of farmers. researchers and goberment. should be eastablished to cooperate effectively. 2) Development of a pricise direct rice seeding machine for both dry and flooding paddy field. which is workable regardless of condition and varieties of seeds. 3) Study on protecting rice seed and seedling from sparrows. 4) Systematic studies of weed control techniques in direct rice seeding to standardize herbicide application. 5) Studies on farm-land reformation. techniques of precise land preparation. and direct rice seeding using an airplane.

• Korean Journal of Weed Science
• /
• v.31 no.2
• /
• pp.183-191
• /
• 2011

Weeding effect was investigated based on the leaf stages to several different herbicide treatments for an integrated weed management of herbicide resistant Echinochloa oryzoides to ACCase and ALS inhibitors in a rice field. Efficacy of soil-applied herbicide treatments before resistant E. oryzoides occurred was very effective. Pentaxazon 5% SC showed over 98% of weeding effect although E. oryzoides were emerged 31 days after the treatment. Until the leaf stage of 2.5, five herbicides, azimsulfuron carfenstole 1.05% GR, bensulfuron-methyl benzobicyclone mefenacet 24.52% SC, bensulfuron-methyl fentrazamide 7% SC, bensulfuron-methyl mefenacet oxadiargyl 21.6% SC and mefenacet pyrazosulfuron-ethyl 3.57% GR showed perfect weeding effect. Benzobicyclone mefenacet penoxulam 21.5% SC and mefenacet pyrazosulfuron-ethyl 3.57% GR were effective at the leaf stage of 3.0. It is very important to select the right herbicides for timing and their systematic application for controlling of E. oryzoides resistant to ACCase- and ALS-inhibitors.

• Korean Journal of Weed Science
• /
• v.16 no.4
• /
• pp.309-316
• /
• 1996

In this study, germination characteristics and herbicidal response of green kyllinga(Kyllinga brevifolia var. leiolepsis H.) were investigated. The storage method desirable for a rapid dormancy release was to keep the seed under low temp. and wetting condition for one to two months, or high temp($40^{\circ}C$) and drying condition for three months. The dormancy of rhizome was hardly observed. The optimum temperature for germination of seed and rhizome was around $30^{\circ}C$ and 16-$20^{\circ}C$, repectively. The germination of dormancy-breaked seed was completely dependent on light. Shoot emergence ratio(%) was decreased with increase of planting depth ; for example, only 18% of rhizome segments planted in the depth of 4cm under soil surface emerged above soil surface. Flooding at earlier growth stage resulted in significant decrease in shoot emergence as well as in dry weight. The germinablity of rhizome was almost lost as a decreased in fresh weight reached to 50%. Usually, green kyllinga was sensitive to herbicides such as bentazone, bensulfuron and benfuresate etc. which were known to be effective in Cyperaceae weeds, indicating that green kyllinga can be used as a representative plant in the screening of herbicides for Cyperus weeds.

• Korean Journal of Weed Science
• /
• v.8 no.2
• /
• pp.124-132
• /
• 1988

Herbicides show many kinds of mode of action and are metabolized in many ways. These biochemical patterns are closely related to the efficacy or mammalian toxicity and also to the selectivity of environmental persistance of herbicides, respectively. In this short review, oxygenase will be discussed as to the metabolisms of monuron, EPTC and bensulfuron methyl, and active oxygens will be reviewed from the standpoint of the mode of action of paraquat and diphenylether herbicides.

• The Korean Journal of Pesticide Science
• /
• v.12 no.1
• /
• pp.1-8
• /
• 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
• /
• v.10 no.4
• /
• pp.255-260
• /
• 1990

Seventeen different herbicides were screened to select promising ones for the control of weeds, which may be used in paddy fields transplanted with 8 days old young rice seedlings. Four classes of herbicides were chosen and tested with seedlings grown under different cultivating conditions. Contact herbicides such as diphenyl-ether and oxadiazol showed severe growth retardation of rice seedlings. Carbamate class(dimepiperate), quinoline class (quinclorac), pyrazol class(pyrazolate), acid amide class(mefenacet and pretilachlor), addition of safener (pretilachlor+fenclorim and mefenacet+bensulfuron+dymuron) and unknown class (KC-7079) exhibited normal growth of seedlings. Sulfonyl urea herbicide class(cimosulfuron, bensulfuron, pyrazosulfuron), and oxarane class(tridiphane) showed the slight growth inhibition but recovered shortly.

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

• Korean Journal of Weed Science
• /
• v.11 no.3
• /
• pp.178-186
• /
• 1991

This study was conducted to evaluate the major weeds occurred in direct seeded rice and their compition with rice, and to establish the effective weed control method. The important weeds occurring in dry direct seeded rice were Echinochloa crusgalli, Cyperus amuricus, Rorippa islandica, etc. Among them, Echinochloa crusgalli was the most dominant weed species. In view of the Simpson's dominance index, the maximum number of the weeds was observed at 30 days after seeding, showing 0.26, but decreased as the time passed. In other hand, Simpson's dominance index of weed dry weight increased from 0.09 at 15DAS(days after seeding) to 0.28 at 60DAS indicating that particular weed such as barnyardgrass was dominating the fields. The plant height and the tiller number of rice in the dry direct seeded rice were not greatly affected by the time and duration of competition with weeds, but rice yield was greatly influenced by them. The yield reduction was observed when compition between rice and weeds were initiated at 20 to 40 DAS till the harvesting time. The highest weed control efficacy was observed at the treatment of systematic herbicide application such as soil applied Butachlor followed by Mefenacet/Bensulfuron-methyl/Dymron at 30 DAS after seeding, and soil applied Dimepiperate/Bensulfuron-methyl mixture as a preemergence type gave also an excellent control.

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