• Korean Journal of Weed Science
• /
• v.16 no.3
• /
• pp.187-193
• /
• 1996

To supply seeds with a good quality as plant materials for herbicide screening and to know whether the germination characteristics could be associated with a differential response to herbicides, germination characteristics and differential responses to herbicides were investigated with 3 species of a genus Setaria ; Yellow foxtail(Setaria glauca P. Beauv, SETGL), Giant foxtail(Setaria faberi Hetrm, SETFA), and Green foxtail(Setaria viridis P. Beauv, SETVI). Degree of dormancy was high in the order of SETGL, SETVI and SETFA. The dormancy of SETGL seed was relatively well removed by room temperature and drying storage, but SETFA and SETVI by low temperature and wetting storage(stratification). For breaking dormancy of SETGL, SETVI and SETFA, it was necessary for being kept under the above storage conditions for at least 2, 4 and 4-5 months, respectively. When the dormancy-breaked seeds were transfered to low temperature($4^{\circ}C$) and drying condition, SETGL showed germination rate of 96% even after 2 month storage. However, SETVI and SETFA showed a decreased germination of 54% and 69%, respectively, with a decreased velocity of germination, indicating that secondary dormancy might be induced. On the other hand, a significant change in germination rate was not observed as the seeds were transfered to room temperature($25^{\circ}C$) and drying condition. The germinability of SETGL seed began to decline from 6th year after storage in room temperature and drying condition. All of 3 species showed relatively high germination rate at alternating temperature of $30^{\circ}C$/$20^{\circ}C$(14hr/10hr) and their germination were not increased by light. All of 3 species exhibited similar responses to cycloxydim, sethoxydim and primisulfuron in greenhouse experiment. In contrast, SETVI and SETFA were relatively susceptible to fenoxapropethyl, SETFA to fluazifop-butyl, SETGL and SETFA to clorimuron-ethyl, and SETGL to EK-2612. The difference in herbicidal response among 3 species was the highest in the treatment of EK-2612. These results suggest that there is no a consistent tendency in responses of 3 species to herbicides which have the same target site. And the relationship between germination characteristics and differential responses to herbicides was not found.

• 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.18 no.2
• /
• pp.146-153
• /
• 1998

This experiment was conducted to clarify the characteristics of germination and emergence of Panicum dichotomiflorum which is a noxious weed species in direct-seeded rice field. P. dichotomiflorum was planted with several treatments such as different depths of irrigation to verifiy the ecological habits of seedling emergence and growth. In order to know the germination characteristics, Panicum dichotomiflorum seeds, pretreated with low-temperature($4^{\circ}C$) stratification for breaking the dormancy, were germinated under different temperature regimes and water potentials. Germination rates of P. dichotomiflorum was increased from 0% of dormant seed to 1%, 35% and 44% by stratification for 21, 28 and 42 days, respectively. Two dominant weed species in directseeded rice fields, Echinochloa crus-galli and Panicum dichotomitlorum, showed different germination habit under different temperature regimes. Echinochloa crus-galli showed more higher germination rate than Panicum dichotomiflorum at relatively low temperature regime(20/$10^{\circ}C$). Both species germinated faster at 30/$20^{\circ}C$ than at 20/$10^{\circ}C$. When the water potential was lowered, germination of Panicum dichotomiflorum was reduced more drastically than Echinochloa crus-galli. The critical water potential for germination of P. dichotomiflorum was -0.7MPa but Echinochloa crus-galli was affected slightly by the same water potential. The results showed that Echinochloa crus-galli can germinate under more wide range of soil water potential than Panicum dichotomiflorum. Emergence of P. dichotomiflorum was highly affected by irrigation depth and the level of water table. When the depth of irrigation water was increased, emergence of P. dichotomiflorum was dragged and emergence rate showed significant difference under the irrigation depth deeper than 6cm. The maximum depth of irrigation water for survival of Panicum dichotomiflorum seedling was 9cm.

• Weed & Turfgrass Science
• /
• v.2 no.1
• /
• pp.55-61
• /
• 2013

This study was carried out to investigate the morphological and soil characteristics of Zoysia spp. native to South Korea. Samples [41 ecotypes of Zoysia japonica, 28 ecotypes of natural hybride between Z. japonica and Z. sinica (Junggi), 22 ecotypes of Z. sinica, and 8 ecotypes of Z. matrella] were collected in seashores, levee and summit of the rock in southern Korea. Variations in leaf width, plant height, leaf angle, length of leaf sheath, leaf trichome, stolon length, and seed shape were measured at collection sites and experimental plots. Among the entries, most of the measurements did not show any significant differences between natural and experimental plot except for leaf angle of Z. sinica and the number of seeds per spike of Z. matrella, which might be caused by different environmental conditions. Soil pH was 6.0 at the most of the collection sites. $Mg^+$ was 0.06-0.02 $cmol{_c}^+kg^{-1}$, $Mg^{2+}$ was 0.09-0.03 $cmol{_c}^+kg^{-1}$, and $K^+$ was 0.02-0.007 $cmol{_c}^+kg^{-1}$ at most zoysiagrasses growing soils.

• Korean Journal of Weed Science
• /
• v.8 no.2
• /
• pp.169-175
• /
• 1988

This experiment was conducted to determine the presence of allelopathic substance in Portulaca oleracea L. Water and methanol extract from P. oleracea markedly inhibited the germination of lettuce, rice, raddish etc., indicating the presence of biological substances. The biochemical substances such as ferulic, p-coumaric, salicylic, vanillic, p-hydroxybenzoic acid etc., belonging to phenolic compounds were detected in a large amount, which may be responsible for exhibiting inhibitory effects. Various phenolic compounds were detected from different samples such as freshly, dried plants, seeds and callus. The highest amount of tannic and gallic acids were detected in dried samples of P. oleracea, the highest grantity of salicylic and vanillic acids in fresh samples, the largest amount of ferulic acid in seed sample, the highest amount of p-hydroxybenzoic and p-chlorobenzoic acids in callus. Linolenic acid was presented in amount of 9.203 mg/g in dried plant of P. oleracea as one of the major fatty acids and oxalic acid presented 27.941 mg/g as one of the major organic acids. These compounds seemed to be related to inhibitory effect of P. oleracea which needs further study.

• Korean Journal of Weed Science
• /
• v.6 no.1
• /
• pp.13-17
• /
• 1986

This experiment was carried out to study the germination behavior and the density effect of Capsella bursa-pastoris Medicus on barley yields. Seed dormancy of C. bursa-pastoris was broken on middle of July. No light was required for germination of C. bursa-pastoris seeds. Higher germination showed at $15^{\circ}C$ than at $0^{\circ}C$ or $6^{\circ}C$. Effective temperature for dormancy breakdown of seed was at $5^{\circ}C$ for 30 days rather than at $40^{\circ}C$. Reduction in barley yield showed with increasing the plant density of C. bursa-pastoris.

• Korean Journal of Weed Science
• /
• v.14 no.4
• /
• pp.252-257
• /
• 1994

The sprouting characteristics of Scirpus planiculmis and storage methods of corm for the herbicide screening were investigated under both laboratory and greenhouse conditions. Sprouting and elongation of S. planiculmis corms were continued during storage at low temperature ($5^{\circ}C$) and wet condition. However, sprouting of corm was failed when the surface water was removed from the corm, and elongation was reduced by the treatment of 0.5-1.0% sodium chloride(NaCl) solution. Alternate temperature was more effective on the sprouting of S. planiculmis corm than constant temperature. Optimum temperature for the sprouting of S. planiculmis corm was alternation between $25^{\circ}C$ to $35^{\circ}C$. Storage at $-20^{\circ}C$ for 10 min. or 14.7% dehydration made the corm of S. planiculmis to fail for sprouting. S. planiculmis corm was more tolerant to sodium chloride than Echinochloa crus-galli or Oryza sativa(Donginbyeo) seeds. Sprouting rate was decreased by cutting of the corm. Sprouting percent by vertical cuttings, horizontal cuttings, and vertical plus horizontal cuttings were 72, 56, and 28%, respectively.

• Korean Journal of Weed Science
• /
• v.17 no.1
• /
• pp.59-65
• /
• 1997

Bentazon 6-hydroxylase (B6H) and cinnamic acid 4-hydroxylase (CA4H) activities were determined in rice (Oryza sativa L.) microsomes to study methods of enhancing cytochrome P-450 mediated aryl hydroxylation of bentazon by hydoxylase inducing compounds. Pretreating rice seeds with 1,8-naphthalic anhydride at 0.5-2% and fenclorim at 5 and 10 ${\mu}M$ increased B6H and CA4H activities. Treatments of rice seedling with ethanol 2.5% enhanced B6H and CA4H activities, and with phenobarbital at 12 mM enhanced B6H activity, and CA4H activity was enhanced at 2 mM. B6H activity was synergistically enhanced by combined treatments of ethanol 2.5 or 5% and phenobarbital 8 or 12mM and also that of 1,8-naphthalic anhydride 0.5 or 1% and phenobarbital 8 or 12 mM, but CA4H activity was decreased by combined treatment. Five-day-old rice seedlings showed higher B6H and CA4H activities which decreased with seedling age.

• Weed & Turfgrass Science
• /
• v.2 no.4
• /
• pp.362-367
• /
• 2013

This study was conducted to develop an efficient control method for water foxtail in the field sowing barley and wheat seeds before rice harvesting. When thifensulfuron-methyl (75%) was applied 0, 5 and 10 days after rice harvesting, little phytotoxicity was observed on both barley and wheat. Percent of water foxtail control with thifensulfuron-methyl (75%) was more than 88% at three different application timing. When butachlor (5%) was applied 5 days before barley and wheat sowing, phytotoxicity on barley and wheat was severe. However, no phytotoxicity was observed on barley and wheat 5 and 10 days after rice harvesting. Percent of water foxtail control with butachlor 0 and 5 days after rice harvesting was 85-89%. However, it dropped to 74-80% when applied 10 days after rice harvesting. In the thifensulfuron-methyl treatment, the dry matter of barley and wheat was 96-108% and 100-108%, respectively when compared with untreated control. While, in the butachlor treatment, the dry matter of barley and wheat was 53-73% and 106%, respectively when compared with untreated control. Therefore, we recommend thifensulfuron-methyl (75%) 0-10 days after rice harvesting or butachlor (5%) 5 days after rice harvesting to provide efficient water foxtail control and safe barley and wheat production.

• Weed & Turfgrass Science
• /
• v.7 no.2
• /
• pp.166-169
• /
• 2018

Repeated use of ACCase inhibiting herbicides for a long time has resulted in increases of resistant Echinochloa oryzicola populations in paddy fields in middle west area of Korea. This study aims to investigate current status of herbicide resistant E. oryzicola in Gyeongsangnam-do, in which there is less information about herbicide resistance. For resistance frequency and dose-response study, seeds from 100 individual plants of E. oryzicola in Gyeongsangnam-do were collected and tested with cyhalofop-butyl. Seven percent of plants from Gyeongsangnam-do was resistant at a recommended rate of cyhalofop-butyl. $GR_{50}$ values (herbicide rates required to reduce plant growth 50%) for one representative resistant populations and five susceptible populations were $738g\;a.i.\;ha^{-1}$ and 66-234 (average 147)$g\;a.i.\;ha^{-1}$, respectively, indicating average 5 times difference in resistance. Although lower rate of frequency of herbicide resistance in Gyeongsangnam-do than in Jeollabuk-do, increases of herbicide resistance are expected in this area because of increases of direct seeded rice fields and increases of dependence on a specific herbicide. Therefore, it is necessary to monitor herbicide resistance regularly and conduct integrated herbicide resistance management in this area.