• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.290-294
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• 2009

Larval development of Nannopaya pygmaea Rambur (Libellulidae), an endangered dragonfly in Korea, was studied using an introduced lariat population in an artificial wetland habitat. Artificial habitat was created in a green house which imitated a small wetland in Boryeong-si, Chungcheongnam-do, Korea, where N. pygmaea inhabited. A total of 300 N. pygmaea larvae were introduced to the artificial habitat in June 2007. Larvae were recaptured five times between June 2007 and November 2008 for measurement of body length. As a result, the initial and recaptured populations (Recaptured I, II, III, IV, and V populations, respectively) contained two body size groups [initial 6.20$\pm$0.34 mm and 7.94$\pm$0.46 mm (mean$\pm$SD); Recaptured I 2.84$\pm$0.43 mm and 5.16$\pm$0.83 mm; Recaptured II 5.96$\pm$0.66 mm and 8.02$\pm$0.35 mm; Recaptured III 5.97$\pm$0.73 mm and 7.82$\pm$0.37 mm; Recaptured IV 7.04$\pm$0.93 mm and 8.52$\pm$0.39 mm; Recaptured V 5.72$\pm$0.60 mm and 7.71$\pm$0.30 mm]. Our rearing experiment evidenced that the recaptured I-V populations are the offspring of the initial population and the offspring grew approximately 3 mm at 470 degree days. It was also estimated that N. pygmaea larvae need approximately 100 degree days to grow 0.7 mm in body length.

• Korean Journal of Weed Science
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• v.4 no.2
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• pp.130-134
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• 1984

This experiment was conducted to know critical sowing depth and emergence day under different sowing depth at Crop Experiment Station, Suweon, in 1982. Tested weed species were Sagittaria pygnaea, Eleocharis kuroguwai, Cyperus serotinus and Potamageton distinetus, sowing depth of weeds were 5cm, 10cm, 15cm, 20cm and 25cm Critical emergence sowing depth of S. pygnaea, E. kuroguwai was 15cmand C. serotinus was 20cm sowing depth while P. distintus was 25cm sowing depth. Average emergence days under 5cm sowing depth for E. kurogwai, S. pygmaea, P. distintus and C. serotinus was 27.8 days, 14.1 days, 13.6 days and 7.3 days. While, relationships between sowing depth and day to emergence was positively correlated. Gernination percent of weeds under Critical emergence sowing depth, S. pygmaea, E. kurogwai and, P. distinctus was 57%, 67%, 80%, but C. serotinu.s was all died.

• Korean journal of applied entomology
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• v.25 no.2 s.67
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• pp.121-128
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• 1986

Six species of Gracillariidae ; Gracillaria ussuriella (E.), Liocrobyla kumatai K., Phyllonorycter leucocorona (K.), P. orientalis (K.), P. pygmaea (K.), Leutospilatrix omissella (S.) and one species of Lyonetiidae: Proleucoptera celastrella K. are reported for the first time from Korea. Also a list of host plants of the total known species of the both families with newly surveyed hosts during the study and some known hosts in home or abroad, is prepared.

• Korean Journal of Weed Science
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• v.1 no.1
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• pp.69-77
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• 1981

Six herbicides were evaluated to investigate the phytotoxicity of rice plant and the weeding efficacy influenced by the time of application in mechically transplanted paddy field. The amount of each chemical applied was 3 kg, a. i, /ha. Chlormethoxynil : Rotala indica KOEHNE and Lindernia pyxuiaria PHILCOX were effectively controlled when applied on the 12th day after transplanting (12 DAT) and this herbicide was excellent for the control of Echinochloa crusgalli P. BEAUV, Monochoria vaginalis PRESL and Sagittaria pygmaea MIQ, when applied early (7 days after puddling) but its weeding effect for these weeds decreased greatly as the application time became later. It had a controlling effect for Potamogeton distinctus A. BENN, Cyperus serotinus ROTTB and Scirpus hotarui ROXB at the initial period at the earlier application time. Butachlor was effective in controlling E. crusgalli, R. indica and L. pyxidaria at 12 days after transplanting (DAT) but was not effective in controlling P. distinctus and S. pygmaea even at the early application time. M. vaginalis, C. serotinus and S. hotarui were effectively controlled by the butachlor treatment at 7 days after final puddling (2 DBT-SDAT) but this weeding effect decreased at the late application time. A combination of butachlor and naproanilide excellently controlled E. crusgalli, R. indica, L. pyxidaria and S. pygmaea regardless of the application time. For the control of M. vaginalis, C. serotinus and P. distinctus, the weeding effect of this mixtures was much greater than that of the single treatment of butachlor. Perfluidone was excellent for the control of E. crusgalli, R. indica, L. pyxidaria, M. vaginalis and S. pygmaea at either application time tested. P. distinctus, C. serorinus and S. hotarui could be controlled by this chemicals until the time of first observation (23 DAT) but the effect for these weeds somewhat decreased as time passed. The effect of pyrazolate on E. crusgalli, M. vaginalis, S. hotarui and P. distinctus was very excellent regardless of the application time but R. indica and L. pyxidaria could not be completely eliminated by this chemical. This chemical was effective in controlling C. serotinus when applied at 7-9 days after final puddling and showed a controlling effect for S. hotaruionly at the initial period. Piperophos + dimethametryn was very excellent for the control of all the annual weeds and P. distinctus. It showed a controlling effect on S. pygmaea, C. serotinus and S. hotarui only at the initial period. There was no difference in the effects on phytotoxicity and yield between chlormethoxynil and pyrazolate at either times of application tested. The later the application time was, the less the phytotoxicity of butachlor and piperophos+dimethametryne was. The phytotoxicity of butachlor + naproanilide and perfluidone decrease in the plots treated at the later application time. When the last two chemicals were treated at 2 days before transplanting (DBT) the yield decreased as compared with the hand weeded plot.

• Korean Journal of Weed Science
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• v.11 no.3
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• pp.187-194
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• 1991

Absorption and translocation, and metabolism studies using $^{14}C$-naproanilide were conducted to determine selective mode of action of naproanilide in rice and paddy weeds under different temperature conditions. Absorption amount of $^{14}C$-naproanilide was greater in Cyperus serotinus and Sagittaria pygmaea than rice and Echinochloa crusgalli. Especially, absorption of $^{14}C$-naproanilide in C. serotinus was increased twice at 32 $^{\circ}C$ and 48 hour exposure conditions. $^{14}C$-naproanilide in roots was translocated to shoots very little in rice and E. crusgalli, but S. pygmaea somewhat greater translocation than the other species. In C. serotinus and S. pygmaea, susceptible weeds, metabolic rates of naproanilide into phytotoxic NOP (2-(2-naphthoxy)-propionic acid) and NOPM (methyl 2-(2-naphthoxy) propionate) were significantly greater than in rice and E. crugalli, tolerant species. Consequently, differential uptake by roots and the difference in activation metabolism of naproanilide among species may explain the possible mechanism of selectivity.

• Korean Journal of Weed Science
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• v.15 no.4
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• pp.321-328
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• 1995

Absorption, translocation, and metabolism study of $^{14}C$-bensulfuron were conducted to determine selectivity and herbicidal action of bensulfuron in two rice cultivars and three paddy weeds at different temperatures. 1. Absorption of $^{14}C$-bensulfuron was greater at 30/$25^{\circ}C$ than at 25/$20^{\circ}C$ and also in cv. Sangpung than in cv. Samgang, and Cyperus serotinus and Sagittaria pygmaea showed greater amount of absorption than Echinochloa crus-galli. 2. Translocation rate of bensulfuron was higher at 30/$25^{\circ}C$ than at 25/$20^{\circ}C$ and also in cv. Sangpung than in cv. Samgang, and C. serotinus showed highest translocation rate followed by the S. pygmaea and E. crus-galli. 3. In metabolism study, concentration of parent compound in rice plants was greater in cv. Sangpung which was susceptible to bensulfuron than in cv. Samgang. More amount of parent compound was distributed in shoots and root of C. serotinus and S. pygmaea than E. crus-galli. 4. It may suggested that sensitivity to bensulfuron between rice cultivars may be due to different inactivation metabolic ability and phytotoxicity of rice increased at high temperature since higher amount of bensulfuron was absorbed. Higher herbicidal activity of bensulfuron may caused by higher absorption and translocation in three weed species at high temperature.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.3
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• pp.310-318
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• 1983

Four methods of vegetation analysis were compared to determine the most suitable method to use in transplanted rice. The highest number of weed species, 14 was obtained with the list quadrat method while the least number, 8 was obtained with the line intercept method. The clip quadrat method tended to overestimate weed species with a low moisture content such as Sagittaria trifolia L. and Ludwigia prostrata Roxb while for the list quadrat method, weed species with a high moisture content such as Sagittaria pygmaea Miq. and Monochoria vaginalis (Burm. f) Pres 1 were overestimated. With the line intercept method, weed species having conspicuous leaf blades such as S. trifolia and Potamogeton distinctus Benn. were dominant. Of the methods tested, the line intercept method was the least desirable because it accounted for the least number of weed species. Any of the others could be use for vegetation analysis without any significant problems arising. However, preference was given to the point quadrat method because of the ease of measurement. It was also less tedious and less time consuming than the other methods.

• Korean Journal of Weed Science
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• v.10 no.3
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• pp.197-201
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• 1990

Emergence and growth of Potamogeton distinctus, Eleocharis kuroguwai, and Sagittaria pygmaea were examined at soil temperatures of 12, 15, 18, 22, 26, and $30^{\circ}C$ and 3 planting depth conditions. Optimum soil temperatures for emergence were 15-$22^{\circ}C$ 22-$26^{\circ}C$, and 18-$26^{\circ}C$ for P. distinctus, E. kurogueai, and S. pygmaea, respectively. Emergence was delayed and growth became poor in three species as planting depths were increased and this trend was more significant in E. kuroguwai.

• Weed & Turfgrass Science
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• v.5 no.1
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• pp.1-4
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• 2016

The Rural Development Administration of Korea conducted a series of surveys of paddy weeds from 1971 to 2013 in approximately 10-year cycles and the results have been used for the efficient weed management of paddy fields. In 1971, annual weeds such as Rotala indica, Eleocharis acicularis f. longiseta, and Monochoria vaginalis were dominant. In 1981, the population of Echinochloa species decreased whereas broadleaf weeds such as M. vaginalis, Sagittaria pygmaea, and S. trifolia were dominant. In 1991, perennial weeds such as Eleocharis kuroguwai, S. pygmaea, and S. trifolia were dominant over annual weeds. In 2000, M. vaginalis was the most abundant species, followed by E. kuroguwai, Echinochloa species, and S. trifolia. In 2013, herbicide-resistant Echinochloa species and M. vaginalis were most dominant, followed by E. kuroguwai, Scirpus juncoides, and S. trifolia. It has been predicted that the prevalence of Echinochloa species will continue to increase and that perennial weeds will be more abundant than annual ones in the near future. The occurrence of herbicide-resistant weeds and exotic weeds will also increase due to global warming and changes in agricultural patterns.

• Korean Journal of Weed Science
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• v.32 no.2
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• pp.127-132
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• 2012

Field survey on the weed occurrence and the use of herbicides was carried out targeting 214 rice cultivating farmers at Gyeongsangbuk-do. 96.2% of farmers did machine planting in late May and this is 68.0% of total cultivating area. Spring plowing was first with 54.6%, followed by spring-fall and fall plowing with 24.8% and 15.0%, respectively. 75% of the farmers treated herbicide twice. 57.5% of them treated herbicide before transplanting and treated at post-emergence again. In case of only application, 84% of the farmers treated herbicide before transplanting. Twenty-three species were occurred at Gyeongsangbuk-do and Echinochloa spp. was the most dominant with 20.8%, Sagittaria trifolia was second with 10.4%, followed by Monochoria vaginalis and Sagittaria pygmaea with 9.9% and 9.7%, respectively. Sagittaria pygmaea was the most difficult to control followed by Echinochloa spp., M. vaginalis, and S. trifolia.