• Korean Journal of Weed Science
• /
• v.31 no.3
• /
• pp.289-293
• /
• 2011

Field experiments were conducted to predict rice yield losses caused by Echinochloa crus-galli (L.)P. Beauv., Bidens frondosa L. and Aeschynomeme indica L. at a range of plant densities under machine transplanted rice cultivation in different regions of Korea in 2006, and to determine their economic threshold levels (ET). All data were fitted to Cousens' rectangular hyperbola to estimate parameters for predicting rice yield loss. The rice yield loss models of Bidens frondosa L. was predicted as y=5.43/(1+0.0113x), $R^2$=0.963, A. indica was y=5.47/(1+0.0332x), $R^2$=0.976 and E. crus-galli y=5.43/(1+0.01552x), $R^2$=0.950. The mean competitivities represented by the parameter, whose reciprocal ($1/{\beta}$) is a weed density reducing crop yield by 50%. Those of E. crus-galli, B. frondosa and A. indica were 0.01552, 0.01113 and 0.0332 in normal-season machine transplanting of Korea, respectively. Single year mean economic thresholds (ET) of A. indica were 0.5, 0.6 and 0.7 plant $m^{-2}$ with the application of flucetosulfuron, flucetosulfuron+imazosulfuron GR and flucetosulfuron+imazosulfuron+carfentrazone GR herbicides, respectively. Meanwhile ET values of 1.6, 1.9 and 1.9 plants $m^{-2}$ for B. frondosa, 1.2, 1.4, and 1.4 plants $m^{-2}$ for E. crus-galli.

• Korean Journal of Weed Science
• /
• v.30 no.3
• /
• pp.183-190
• /
• 2010

The objective of this study was to isolate a herbicidally active compound from curly dock (Rumex crispus), a native weed in Korea and to identify its' chemistry. The $GR_{50}$ value of methanol extracts which is determined by a seed bioassay using rapeseed (Brassica napus) seedlings was $935\;{\mu}g\;g^{-1}$. Activity-directed isolation of ethylacetate extract led to the isolation of ECDA fraction with $GR_{50}$ value $53\;{\mu}g\;g^{-1}$. Based on data of GC-MS, $^1H$-NMR and $^{13}C$-NMR, the chemical structure of ECDA was determined as 2H-furo[2,3-H]-[1]-benzopyran-2-one which is known as angelicin. The $GR_{50}$ values of angelicin to barnyardgrass (Echinochloa crus-galli), southern crabgrass (Digitaria ciliaris), and indian jointvetch (Aeschynomene indica) were 426, 66 and $216\;{\mu}g\;g^{-1}$, respectively. Our results suggest that angelicin could be used as a lead compound for the development of new herbicides.

• Weed & Turfgrass Science
• /
• v.2 no.3
• /
• pp.283-291
• /
• 2013

This experiment was carried out for the selection of suitable cultivars on the green and fairway at the mountain area. The climate data showed that differences of altitude influenced greater than latitude on temperature and rainfall when compared with 3 areas of the central of Gyeong-gi and Yeong-seo, and the mountain area at Yeong-seo. The plot was prepared with the USGA profiles for green and modified California style for fairway at the mountain golf course in Wonju, Korea. The growth characteristics were compared on two different profiles for 3 years of growing seasons after seeding with 5 creeping bentgrass cultivars. 'T-1' and 'CY-2' showed a rapid greenup compare with other cultivars in spring of 2010 with the both green and fairway mowing height. However, 'Penncross' resulted the slowest among cultivars. 'T-1' showed the most prominent visual quality of overall rate and the deepest root length after one year of seeding, while 'Penncross' showed an excellent result of root length and weight during summer season. However, 'Penn A-1' had an imperial result in that season. Comparison of the growth characteristics under green and fairway conditions, 'T-1' and 'CY-2' showed exellent overall results at the mountain area at Yeong-seo area in Korea.

• Korean Journal of Weed Science
• /
• v.15 no.4
• /
• pp.298-304
• /
• 1995

This study was carried out to make the most of them as the fundamental data for reasonable weed control when population of weeds was observed in the alternated fields of lowland and upland. The annual and the perennial paddy weeds in the continuous paddy rice field remarkably decreased when compared to that in the alternated field of paddy rice and soybean. The longer was the duration of upland field condition, the less was the population of lowland weeds and the more was the population of upland weeds. Biennial weeds in the contiuous paddy rice field were less than that in the rotated field of paddy rice and soybean, and this tendency was clear in Alopecurus aequalis Sobol. In the continuous cropping of paddy rice, population of biennial weeds in the culverted field was higher than that in the unculverted one, but in the continuous cropping of soybean this tendency was vice versa.

• Korean Journal of Weed Science
• /
• v.15 no.1
• /
• pp.73-84
• /
• 1995

Four malformin A's produced by Aspergillus niger van Tiegh. were separated by HPLC equipped with $C_{18}$ reversed-phase column and subjected to structural determination. Amino acid analyses and mass spectra data of the compounds indicate that they structurally resemble the cyclic pentapeptide malformin $A_1$. Their structures were deduced by two dimensional NMR and MS/MS experiments as cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Ile for $A_1$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Val for $A_2$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Leu for $A_3$, and cyclo-D-Cys-D-Cys-L-Val-D-Ile-L-Val for $A_4$. Among the mal-formin A's, the structure of $A_3$ was identical to that of malformin C, which was produced by A. niger strain AN-1. All the malformin A's caused severe curvatures of corn(Zea mays L.) roots and the activities of the malformin A's with molecular weight 529 were greater than those with molecular weight 515. Malformin $A_1$ caused the corn root curvature by 83% at a concentration of $0.25{\mu}M$. In the mung bean(Phaseolus aureus Roxb.) hypercotyl segment test, however, the molecular weight of malformin A's was not a factor influencing the physiological activities. Malformin $A_1$ stimulated the growth of mung bean hypercotyles by 165% at a $0.1{\mu}M$ concentration.

• Weed & Turfgrass Science
• /
• v.4 no.3
• /
• pp.188-198
• /
• 2015

This study was conducted in order to investigate the distribution pattern of weeds and ecological characteristics on the dry field in the Eastern region of Korea. The weed species data were obtained from 12 regions in Gangwon-do and Gyeongsang-do. 150 taxa were recorded from three main distinguished habitats; inside of dry field (IDF), embankment around the end of dry field (EDF), levee slope of dry field (LS). The weed species of three different habitats were IDF 83 taxa, EDF 133 taxa and LS 105 taxa. The species showing higher rNCD value was Portulaca oleracea in IDF, Digitaria sanguinalis in EDF and Humulus japonicus in LS. Compositae was dominant family followed by Gramineae, Polygonaceae and Leguminosae. Life form was distinguished as Th-R5-D4-e and three different habitats showed the same results. Disturbance index was analysed as IDF 83.1%, EDF 68.4%, and LS 62.9%. Naturalized rate was analysed as IDF 28.9%, EDF 22.6%, and LS 20.0%. These results indicate that the weeding management, land use intensity, and human interference effect on the distribution index and naturalized rate of weed.

• Weed & Turfgrass Science
• /
• v.4 no.3
• /
• pp.176-187
• /
• 2015

The weed flora in the Codonopsis lanceolata upland fields were surveyed in Hoengseong and Jeju in May, August, and October of 2014. The objectives of this study were to use the survey data for establishing weed control methods and to bring awareness of possible problematic weeds occurred in C. lanceolata upland fields in Korea. Altogether 207 weed species of 47 families were identified, of which 87 were annual, 47 species were biennial and 73 were perennial. Based on the morphological characteristic of the leaves, 182 species were broad leaves, 18 species were grasses, and 7 species were sedges. The dominance was highest in the Artemisia princeps followed by Digitaria ciliaris, Commelina communis, Persicaria longiseta and Echinochloa crus-galli etc. Fifty-nine species were exotic weeds with 29% of a total presence, of which Erigeron annuus was highest, followed by Crassocephalum crepidioides, Bidens frondosa, Hypochaeris radicata etc. In the PCA plot, weeds presented in the C. lanceolata upland fields of Hoengseong were divided into three groups, E. annuus, Sigesbeckia pubescence and C. communis communities and those of Jeju were divided into four groups, C. crepidioides-Cyperus iria, Spergula arvensis, Poa annua and Youngia japonica communities.

• Weed & Turfgrass Science
• /
• v.4 no.1
• /
• pp.26-34
• /
• 2015

Korean Poaceae includes approximately 80 species of the agricultural weeds. Precise species identification is the first step for more effective weed management in the agricultural fields. However, the identification of species in Poaceae is not easy without the assistance of taxonomists or identification experts although they are relatively easy to distinguish from the plants of the other family by the unique characteristics of caryopsis. Thus, DNA barcode was suggested as an alternative powerful technique for species identification by using short sections of DNA from a specific region of the genome. Two standard barcode markers of vascular plants, chloroplast rbcL and matK, and a supplementary nuclear ribosomal Internal Transcribed Spacer (ITS) region were used for barcode of major Korean Poaceae weeds, 403 individuals of 84 taxa. All the barcode markers revealed a good level of sequencing success with the lowest 73.7% for matK and the highest 88.8% for rbcL. The barcode sequences were deposited to the National Center for Biotechnology Information (NCBI) database for public use. Combined matK and ITS showed very high resolving power with 92.9%. Besides the identification of weeds for weed managment, the generated DNA barcode data could be used for many other applications such as rapid biodiversity assessment and conservation prioritization.

• Weed & Turfgrass Science
• /
• v.4 no.1
• /
• pp.44-48
• /
• 2015

This study was conducted to evaluate the efficacy of weed control and phytotoxicity of oxyfluorfen using a transgenic rice line (CPPO06 event) resistant to protoporphyrinogen oxidase (Protox) inhibiting herbicides in the direct-seeding flooded rice. Five annual weeds including Echinochloa oryzoides and two perennial weeds were occurred in the test field. Oxyfluorfen at 120 g a.i. $ha^{-1}$ in the application timing of two days before sowing and 0 and five days after sowing showed more than 90% weed control value except for Juglans mandshurica. Total weed control value was more than 95% in any application timing indicating a highly effective herbicide in the direct-seeding flooded rice. When compared with untreated control, no visual injuries were detected at single and double dosage of oxyfluorfen. The agronomic characteristics and yield components of CPPO06 event was reasonable in any time of application in this study. Based on these data, oxyfluorfen application before and after sowing can be applied to provide effective weed management in the direct-seeding flooded field.

• Weed & Turfgrass Science
• /
• v.4 no.1
• /
• pp.10-17
• /
• 2015

This study was conducted to investigate the occurrence of weed flora in pastures in Jeju island of Korea and to establish the basic data for controlling them occurred in the pastures. Weed flora was investigated twice, May and July on 2003. There were a total of 207 weed species including 49 families. Among them 67 species were annual, 39 species were biennial and 101 species were perennial. The compositions of major plant families, Asteraceae, Poaceae, Polygonaceae, Rosaceae, Fabaceae were 17, 15, 8, 7, 6%, respectively. Sixty-eight species of exotics were occurred, as well. Rumex obtusifolius was the highest in importance analysis and the followings were in order of Trifolium repens, Artemisia princeps, Plantago asiatica, Potentilla anemonefolia and Rumex acetosella etc. Among the exotic weeds, R. obtusifolius, T. repens, R. acetosella and C. holosteoides var. hallaisanense might be most problematic weeds species in pastures in Jeju island in the future. And at the boundary of some pastures and mountains Smilax china, Duchesnea indica, Rosa maximowicziana, etc. 17 shrub species were also occurred.