Cyperus Difformis Research Articles

Diversities of soil weed seed bank and rice yield performance in response to tillage method and weeding regime

Rice field was infested with eight weed species. Among the species found in conventionally tilled plots, the five dominant species ranked in order of importance value were Cynodon dactylon (L.), Paspalum distichum (L.), Cyperus rotundus (L.), Azolla pinnata (L.) and Cyanotis axillaris (L.) while in stale seedbed the rank was Paspalum distichum (L.), Cynodon dactylon (L.), Cyanotis axillaris (L.), Leersia hexandra (L.) and Cyperus rotundus (L.). There were 15 weed species found in the soil weed seed bank studied at the net house. Among them five species were common of rice field. Ten new species were found in the seed bank. Azolla pinnata (L.), Cyperus difformis (L.) and Paspalum commersonii (L.) of field rice were not found in net house seed bank. In the field, Cynodon dactylon (L.) was the dominant over Paspalum distichum (L.) but at the net house Paspalum distichum (L.) was dominant over Cynodon dactylon (L.). In seed bank under conventional tillage, 11 species were found consisting of 3559 heads count and in stale seedbed 12 species consisting 3826 heads were counted. Among the identified species, nine were common in both tillage practice. Parapholis strigose (Dumort.) and Phyllanthus niruri (L.) were present in the soil of conventional tillage but not in stale bed while Echinochloa colonum (L.), Fimbristylis miliaceae (L.) and Eragrotis gangetica (Roxb.) were found in stale bed but not in conventional tillage. At the rice field grass weeds were dominant over sedges and broad leaf under the both types of tillage. At the seed bank of net house, grass weeds were dominant over sedges and broadleaf under conventional tillage while under stale seedbed, sedges were dominant over broad leaf and grass. Around 7% higher grain was recorded from stale seedbed compared to conventional tillage which attributed from higher number of effective tillers hill-1, higher number of fertile grains panicle-1, and lower number of sterile grains panicle-1. Weed free condition yield the highest grains followed by the combination of pre and post-emergence herbicides and unweeded control yielded the lowest. Stale seedbed kept weed free yielded the highest followed by stale seedbed sprayed the two herbicides. Conventional tillage remained unweeded yielded the lowest grain.Progressive Agriculture 27 (1): 39-47, 2016

A psbA mutation (Val219 to Ile) causes resistance to propanil and increased susceptibility to bentazon in Cyperus difformis.

Propanil-resistant (R) Cyperus difformis populations were recently confirmed in California rice fields. To date, propanil resistance in other weed species has been associated with enhanced aryl acylamidase (AAA)-mediated propanil conversion into 3,4-dichloroaniline. Our objectives were to determine the level of propanil resistance and cross-resistance to other PSII inhibitors in C. difformis lines, and to elucidate the mechanism of propanil resistance. The propanil-R line had a 14-fold propanil resistance and increased resistance to bromoxynil, diuron and metribuzin, but not to atrazine. The R line, however, displayed a fourfold increased susceptibility to bentazon. Interestingly, susceptible (S) plants accumulated more 3,4-dichloroaniline and were more injured by propanil and carbaryl (AAA-inhibitor) applications than R plants, suggesting that propanil metabolism is not the resistance mechanism. psbA gene sequence analysis indicated a valine-219-isoleucine (Val219 Ile) amino acid exchange in the propanil-R chloroplast D1 protein. The D1 Val219 Ile modification in C. difformis causes resistance to propanil, diuron, metribuzin and bromoxynil but increased susceptibility to bentazon, suggesting that the Val219 residue participates in binding of these herbicides. This is the first report of a higher plant exhibiting target-site propanil resistance. Tank mixing of bentazon and propanil, where permitted, can control both propanil-R and propanil-S C. difformis and prevent the spread of the resistant phenotype. © 2016 Society of Chemical Industry.

Weed management in rice under SRI method of crop establishment

A field experiment was conducted during dry seasons of 2011 and 2012 at the ICAR-National Rice Research Institute, Cuttack to study the weed spectrum and efficacy of different weed management practices under system of rice intensification (SRI). Cyperus difformis (23.1%) was the predominant weed flora followed by Echinochloa colona (14.7%) at 45 days after transplanting (DAT) in weedy plots. Management of weeds by operating cono weeder at 15 and 30 DAT was found most effective practice (weed control efficiency 90.8% at 45 DAT) for controlling broad spectrum of weeds and realizing higher grain yield (5.79 t/ha). However, chemical weed control by applying azimsulfuron at 35 g a. i./ha applied 15 DAT was the most economic weed management option for getting higher net returns (Rs. 34, 400/ha) and benefit: cost ratio (2.82). Application of azimsulfuron also showed least energy input (8.6 x 103 MJ/ha) compared with all other weed management treatments.

Herbicides combination for control of complex weed flora in transplanted rice (Oryza sativa L.)

A field experiment was carried out at Norman E. Borlaug Crop Research Centre of G. B. P. U. A. & T., Pantnagar, U. S. Nagar, Uttarakhand during kharif seasons of 2014 and 2015 to evaluate the efficacy of different herbicides and their combinations to control the different weed flora in transplanted rice. The experimental site was silty clay loam in texture, medium in organic carbon (0.66%), available phosphorus (27.5 kg/ha) and potassium (243.5 kg/ha) with pH of 7.3. The experiment was laid out in randomized block design with 12 treatments replicated thrice. In the present study, Echinochloa colona, Echinochloa crus galli, Leptochloa chinensis, Ammania baccifera, Caesulia axillaris, Cyperus iria and Cyperus difformis were found as major weeds in experimental field during both the years. The results revealed that among the herbicidal treatments penoxsulam+cyahalofop-butyl @ 135 g/ha recorded lowest total weed density which was statistically similiar to pretilachlor @ 750 g/ha fb ethoxysulfuron @ 18.75 g/ha, bispyribac-sodium+ethoxysulfuron @ 25+18.75 g/ha, pretilachlor @ 750 g/ha fb readymix of chlorimuron-ethyl +metsulfuron-methyl @ 4 g/ha and pendimethalin @ 1000 g/ha fb bispyribac-sodium @ 25 g/ha. The total weed dry weight was significantly reduced with penoxsulam+cyahalofop-butyl @ 135 g/ha, pendimethalin @ 1000 g/ha fb bispyribac-sodium @ 25 g/ha and pretilachlor @ 750 g/ha fb ethoxysulfuron @ 18.75 g/ha over rest of the herbicidal treatments. The highest weed control efficiency (98.2%) was also recorded with readymix of penoxsulam+cyahalofop-butyl @ 135 g/ha followed by pendimethalin @1000 g/ha fb bispyribac-sodium 25 g/ha, pretilachlor 750 g/ha fb ethoxysulfuron 18.75 g/ha, bispyribac-sodium+ethoxysulfuron @ 25+18.75 g/ha. The maximum grain yield (6.8 t/ha) was recorded with penoxsulam+cyahalofop-butyl @ 135 g/ha which was statistically at par with pendimethalin @ 1000 g/ha fb bispyribacsodium @ 25 g/ha, twice hand weeding at 25 and 45 DAT, bispyribac-sodium+ethoxysulfuron @ 25+18.75 g/ha, pretilachlor @ 750 g/ha fb ethoxysulfuron @ 18.75 g/ha and readymix of triafamone+ethoxysulfuron @ 60 g/ha.

Prevalence of weed flora of transplanted rice in different regions of Haryana

Floristic composition of weeds in transplanted rice was studied by surveys of 199 fields in eight rice growing districts of Haryana state during July-August, 2011 and importance value index (IVI) of individual weeds was calculated by pooling average values of observations of relative density and relative frequency. In all, 28 weed species (7 grassy, 7 sedges and 14 broadleaf) were found to infest rice fields in Haryana. Grassy weeds Echinochloa colona and Echinochloa glabrescence were major weeds found to infest rice fields in all the districts. Similarly, Ammania baccifera with IVI values of 1.6–36.8 among broadleaf weeds and Cyperus rotundus, Cyperus difformis among sedges were also present in all the districts. Broadleaf weed Caesulia axillaris, although with low density, was present in all the north-eastern districts except Karnal whereas presence of this weed was not noticed in any district of south-western Haryana. Sedge Scirpus supinus with IVI of 6.0–36.0 was present in all north-eastern districts except Panchkula and Jind, whereas in south-western districts, it was present only in Jakhal area of Fatehbad and Beri block of Jhajjar district in rice grown under semi-aquatic situations. Leptochloa chinensis, a new emerging grassy weed with IVI values of 11.7–22.6, was rated as one of the important grassy weeds that was found to cause yield losses in light textured soils in all parts of state except Ambala, Hisar, Jind, Rohtak and Jhajjar districts.

A new herbicide mixture: bispyribac sodium+metamifop 14% SE for weed control in wet seeded rice

In direct seeded rice (DSR), weeds are the major biotic constraint in improving the productivity of rice. Acute labour shortage and hike in wage rate force the farmers to rely more on herbicides for weed management in DSR. But the continuous use of same herbicide or herbicides with similar mode of action leads to shift in weed flora and resistance development in weeds. One of the ways to overcome these problems is the use of herbicide mixtures. Hence, field experiments were conducted for two seasons kharif 2014 and rabi 2014–15 to assess the bio-efficacy of bispyribac sodium+metamifop, a post-emergence herbicide mixture for broad spectrum weed control in DSR. The experiment was laid out in randomized block design with seven treatments and three replications. The treatments comprised four doses of bispyribac sodium+metamifop viz., 60, 70, 80 and 90 g/ha, bispyribac sodium @ 25 g/ha, hand weeding twice and weedy check.Schoenoplectus juncoides, Cyperus iria, Cyperus difformis, Fimbristylis miliacea, Isachne miliacea, Ludwigia perennis, Limnocharis flava, Sphenoclea zeylanica, Marsilea quadrifolia, Bergia capensis, Commelina diffussa and Monochoria vaginalis were the major weeds in the experimental field. Among the three morphological groups of weeds, sedges was the most predominant one in the experimental site. Results revealed that compared to bispyribac sodium @ 25 g/ha, bispyribac sodium+metamifop @ 70, 80 and 90 g/ha was found more effective in reducing the density and dry weight of weeds. Application of bispyribac sodium+metamifop @ 90 g/ha registered the highest weed control efficiency of 96.62%. Grain yield was also significantly influenced by the weed control treatments. The highest grain yield (8051 kg/ha) and net returns (Rs. 86238/ha) were recorded in bispyribac sodium+metamifop @ 90 g/ha and it was statistically comparable with the lower doses of 80 and 70 g/ha. Bispyribac sodium+metamifop @ 90, 80 and 70 g/ha was significantly superior to hand weeding twice and bispyribac sodium applied @ 25 g/ha in terms of net returns and B: C ratio.

Occurrence Cause, Mechanism and Control of Herbicide-Resistant Weeds in Rice Field of Korea

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 GR50 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 GR50 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 (I50) 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.

Molecular basis of Cyperus difformis cross-resistance to ALS-inhibiting herbicides

Applications of 64 times higher rates of azimsulfuron and halosulfuron-methyl failed to reduce by 50% growth of 10 putative resistant (R) Cyperus difformis (smallflower umbrella-sedge) populations collected from rice fields located in Northern Greece. However, the growth rate of the susceptible (S) population was reduced by 50% by 1/4 of the recommended rate of both herbicides. The als gene sequencing identified point mutations at Pro-197 position, leading to amino acid substitution by Ala or Ser of the ALS enzyme. The in vitro activity of the ALS enzyme indicated that the I50 values (herbicide concentration required for 50% reduction of the ALS activity) ranged from 10.7 to 55.5μM azimsulfuron and from 6.7 to 50.6μM halosulfuron-methyl, whereas the respective values for the S population were 0.09 and 0.11μM. These results strongly support that cross-resistance of 10 C. difformis populations was due to point mutations of the als gene, which resulted in a less-sensitive ALS enzyme. This study reports the presence of a 1240bp intron in the C. difformis als gene with the Pro-197 point mutations near the splice junction.

ALS-Resistant Smallflower Umbrella Sedge (Cyperus difformis) in Arkansas Rice: Physiological and Molecular Basis of Resistance

Smallflower umbrella sedge is a problematic weed in direct-seeded rice in the midsouthern United States. It recently has evolved resistance to the acetolactate synthase (ALS) –inhibiting herbicide halosulfuron in Arkansas rice. Studies were conducted (1) to determine if the resistant biotype is cross resistant to other ALS-inhibiting herbicides, (2) to evaluate alternative herbicide control options, and (3) to determine the mechanism of resistance. Whole-plant bioassay revealed that halosulfuron-resistant plants were not controlled by bispyribac–sodium, imazamox, and penoxsulam at the labeled field rate of each herbicide. The level of resistance to these herbicides, based on the lethal dose needed to kill 50% of plants (LD50) was ≥ 15-fold compared to a susceptible biotype. Both biotypes were controlled >96% with bentazon and propanil and ≤ 23% with quinclorac, thiobencarb, and 2,4-D. Hence, effective control measures exist; albeit, the number of herbicide options appear limited. Based on in vitro ALS enzyme assays, altered target site is the mechanism of resistance to halosulfuron and imazamox. Massively parallel sequencing with the use of the Illumina HiSeq detected an amino acid substitution of Pro197-to-His in the resistant biotype that is consistent with ALS-inhibiting herbicide resistance in other weed species.

Bio-efficacy of penoxsulam+cyhalofop butyl 6% OD, a new pre-mix herbicide mixture for weed control in direct seeded puddled irrigated rice (Oryza sativaL.)

The field experiments were conducted during kharif and rabi 2014 to study the efficacy of pre-mix herbicide mixture penoxsulam+cyhalofop butyl for weed control in direct seeded puddled rice. The experiment was laid out in randomized block design with eight treatments and three replications. The treatments comprised four different doses of penoxsulam+cyhalofop butyl 6% OD viz., 120, 125, 130 and 135 g a. i./ha, bispyribac sodium 10% SE 25 g a. i./ha, penoxsulam 24 SC 22.5 g a. i./ha, hand weeding twice and weedy check. On 30 days after sowing (DAS) weed flora comprised sedges (53.91%), broad leaf weeds (37.88%) and grasses (8. 2%) and on 60 DAS weed flora constituted sedges (53.15%), broad leaf weeds (BLW) (34.66%) and grasses (12.19%). The dominant weed species present in the experimental field were Schoenoplectus juncoides (Roxb.) Palla, Cyperus iria L. and Cyperus difformis L. among sedges; Isachne miliaceae Roth among grasses and Ludwigia perennis, Limnocharis flava (L.) Buch., Marsilea quadrifoliata L. and Bergia carpensis L. among broad leaf weeds. Pre-mix herbicide mixture, penoxsulam+cyhalofop butyl was found to be effective in reducing the density and dry weight of weeds at 30, 45 and 60 DAS. Among the doses, higher doses of penoxsulam+cyhalofop butyl (130 and 135 g a. i./ha) were found to be more effective in reducing the dry weight with a weed control efficiency of 97.34 and 98.31%, respectively. Higher growth and better expression of yield attributes were registered for these treatments. Adoption of weed control measures enhanced the grain yield from 4.26 to 8.46 t/ha. All the tested doses of penoxsulam+cyhalofop butyl recorded higher grain yield compared to hand weeding, penoxsulam and bispyribac sodium applied alone. Application of penoxsulam +cyhalofop butyl at its higher dose (135 g a. i./ha) recorded the highest grain yield which was on a par with its lower dose 130 g a. i./ha. The highest gross returns and B: C ratio were also recorded by these treatments. Bispyribac sodium was found to be less effective in reducing the density and dry weight of sedges resulting in lesser yield and B: C ratio compared to penoxsulam in the present study. Hand weeding recorded the lowest gross returns and B: C ratio among the weed control treatments. The study concludes that better broad spectrum control of weeds can be achieved by the post-emergence application of herbicide mixture penoxsulam+cyhalofop butyl on 15 DAS. The selection of herbicide and dose should depend on the target weed species in an area.

The Pathogenicity of Sclerotium rolfsii on Cyperus difformis and its Potential Host Specificity among the Genus Cyperus

Sclerotium rolfsii Sacc. infects more than 500 species of monocotyledonous and dicotyledonous plants except Cyperaceae family. The pathogenicity of a S. rolfsii isolate was evaluated by seven Cyperus species in order to explicate host specificity to Cyperaceae family. The results showed that only C. dofformis L. was infected with typical water-soaked lesions of the basal stem, which progressed to rotting, wilting, blighting, and eventually death. The performance of hyphae on the surface of Cyperus plants was compared and found that only stomata of C. difformis were adhered by hyphae of S. rolfsii. The infection process of S. rolfsii on leaf sheath of stem base in C. difformis showed that dense mycelial networks and ramifying hyphae were usually formed on the inoculated tissues, then growing hyphal tips were observed to spread wavelike on the stem surface, reaching the stomata between the leaf veins accurately and directly enter the host through stomata. Differences of the main micro-morphology characters of leaf sheath abaxial epidermis among the seven species were compared. The stomata of C. difformis were always presented between the leaf veins (3 or 4 rows of cells from the leaf veins), while the stomata of tolerant Cyperus species were close to the leaf veins. Underneath the stromata of C. difformis were air chambers, however vascular bundles were always present underneath the stomata of the tolerant Cyperus. Our study indicates that different anatomical structures in genus Cyperus may be associated with resistance to S. rolfsii infection.

Integrated Weed Management in Transplanted Rice (Oryza sativa)

A field experiment was conducted during the kharif season of 2010 and 2011 at the Regional Research Station, Kalimpong (1250 m a.s.l), to find out eff ective and suitable method of weed control in transplanted rice under mid hill conditions. The major weed found in control plot were Echinochloa crus-galli, Echinochloa colonum, Cynodon dactylon Cyperus rotundus, Cyperusiria, Cyperus difformis, Fimbristylis miliaceae, Ammania baccifera, Ludwigia parviflora. Pre-emergence application of metsulfuron methyl + chlorimuron ethyl supplemented with one hand weeding at 40 DAT, provided a broad - spectrum weed control and was significantly superior to rest all other integrated approach of weed control. The highest weedcontrol efficiency (91.4%) was also recorded under this treatment. The grain yield was highest with hand weeding thrice (6.61 t/ha) which was comparable with treatment of metsulfuron methyl + chlorimuron ethyl (0.005 kg/ha) supplemented with one hand weeding (6.47 t/ha). The highest benefit: cost ratio was with metsulfuron methyl + chlorimuron ethyl (0.005 kg/ha) supplemented with one hand weeding at 40 DAT (2.18) and was followed by pretilachlor (0.5 kg/ha) followed by one hand weeding (2.14). Metsulfuron methyl + chlorimuron ethyl (0.005 kg/ha) followed by one hand weeding at 40 DAT controlled weed population and gave yield a ributing traits and yield comparable to those of hand weeding thrice and proved more remunerative than other weed management practices.

전북지역 제초제 저항성 논 잡초 발생분포 및 제초제 사용실태

This study was conducted to obtain basis information for effective weed control by the fact-finding survey of herbicides use at farmer’s level and distribution of herbicide resistant weeds in paddy field of Jeonbuk province, Korea. The distributions of major paddy field weeds and frequently used herbicide according to the survey were as follows. The dominant weeds in rice paddy field were Echinochloa crus-galli, Eleocharis kuroguwai, Scirpus juncoides, Monochoria vaginalis, etc.. Preferred herbicides widely used by farmers were ranked in the following order, early and middle treatment (48.0%), treatment before transplanting (36.7%) and foliar treatment (15.3%). The occurrence of herbicide-resistant weeds according to collected paddy soils was as follows. The occurring area of herbicide-resistant weeds was 24,413 ha, approximately 18.4% of rice cultivation area. Herbicideresistant weeds were occurred in four species. The order of occurrence were Scirpus juncoides (39.0%) ＞ Monochoria vaginalis (27.8%) ＞ Echinochloa crus-galli (16.6%) and Cyperus difformis (16.6%). This information could be useful for estimation of future herbicide-resistant weed and establishment of herbicide-resistant weed control methods in Jeonbuk province, Korea.

Host suitability of weeds and forage species to root-knot nematode meloidogyne graminicola as a funcion of irrigation management

The irrigated rice production can be limited by various phytopathogenic agents, including root-knot nematodes (Meloidogyne spp.). Thus, the aim of this research was to check the host suitability of plant species most often found off-season and during rice cultivation, to root-knot nematode Meloidogyne graminicola, under two irrigation managements. Two experiments were conducted in a completely randomized design. In the first experiment seven plant species that occur in an area of rice cultivation, in fallow, off-season were evaluated. For the second experiment nine weed species infesting the irrigated rice culture were tested in rainfed and flooding conditions. The sixteen species, kept individually in pots with sterilized substrate, were inoculated with 5,000 eggs and second stage juveniles (J2) of nematode. BRS 410 IRGA rice plants inoculated with M.graminicola were used as control. Two months after inoculation, the root system of each plant was evaluated for number of galls and nematode reproduction factor. It was verified that the species of off-season of rice cultivation Sida rhombifolia, Raphanus raphanistrum, Spergula arvensis, Lotus corniculatus and Trifolium repens, and, during the cycle of rice cultivation, Aeschynomene denticulata, Leersia hexandra, are immune to nematode. The plant species off-season, Avena strigosa and Lolium multiflorum and of cultivation, Alternanthera philoxeroides, red rice, Echinochloa crusgalli, Cyperus difformis, Cyperus esculentus, Cyperus iria and Fimbristylis miliacea would behave as hosts of M.graminicola, mostly under rainfed conditions.

Weed community composition after 43 years of long-term fertilization in tropical rice–rice system

Biodiversity is central to the study of biology and research on the effects of human activities on biodiversity is becoming increasingly important as extinction levels increase. Many factors are increasing extinction levels, and continuous nitrogen application may be one of the reason driving terrestrial extinctions. Understanding the response of arable weed community assembly to fertilization is important for designing better weed management strategies in tropical rice–rice systems and also for changes in weed biodiversity. The cumulative effects of various fertilization treatments on weed species composition and diversity along with rice growth and yield were investigated in a long-term fertilizer experiment established 43 years ago in CRRI, Cuttack, India. A total of 20 weed species were observed in the study, out of which 6 species (i.e., Cyperus difformis, Cyperus tenuspica, Fimbristylis miliacea, Echinochloa colona, Oldenlandia corymbosa, Lindernia anagallis) occurred in all treatments and remaining species occurred only in some of the treatments. Sedges were dominant in all the treatments followed by broad-leaves and grasses, high relative density of weeds was observed in control and FYM treated plots, whereas, low weed density was observed in N, NPK and NPK+FYM treatments. The indices of species diversity (species richness, Shannon–Wiener, Pielou and Simpson indices) showed linear relationships with rice yield. The balanced fertilization was more efficient at inhibiting the potential growth of weeds because of the increased growth of rice leading to competition for nutrients. Principal component analysis showed that changes in the weed community composition were due to application of P and FYM. Balance fertilization showed a positive effect on rice yield and negatively affect weeds density, although the effect is negative but balance fertilization is not resulted in species elimination or hampered biodiversity.

한국 논에서 제초제 저항성잡초의 발생 현황, 메카니즘 및 방제

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 <TEX>$GR_{50}$</TEX> 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 <TEX>$GR_{50}$</TEX> 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 (<TEX>$I_{50}$</TEX>) 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 [<TEX>$^{14}C$</TEX>]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.

Cyperus difformis evolves resistance to propanil

Cyperus difformis L. is one of the worst weeds of rice world-wide and has evolved resistance to acetolactate synthase (ALS)-inhibiting herbicides in rice fields of California. Propanil use was intensified to control the widespread resistant biotypes. Rice growers have recently experienced poor control, suggesting resistance to this photosystem II-inhibiting herbicide may have evolved in C. difformis populations. The objectives of this study were to detect the presence of propanil resistance, to establish resistance levels, and to investigate involvement of enhanced herbicide detoxification as mechanism of resistance through the use of metabolic inhibitors. Four C. difformis populations collected in rice fields from the Sacramento Valley of California were confirmed resistant to propanil. This is the first case of such resistance outside the Poaceae and the first time C. difformis exhibits resistance to an herbicide mechanism of action other than ALS inhibition. Carbaryl and malathion applied individually in mixture with propanil had minor effects on herbicide toxicity suggesting metabolic detoxification was not a resistance mechanism. A resistant biotype produced more than 80% biomass after a propanil (6.7 kg a.i. ha−1) and carbaryl (1.9 kg a.i. ha−1) or propanil and malathion (1.0 kg a.i. ha−1) treatment compared to <20% by a susceptible biotype, suggesting substantial resistance still persisted in spite of insecticide addition. Propanil-resistant plants were cross-resistant to bensulfuron-methyl, imazosulfuron, halosulfuron-methyl and penoxsulam, but susceptible to carfentrazone. The loss of propanil to control this important weed of rice underscores the fragility of herbicide-based weed control in monoculture rice. Integrated weed management approaches to decrease herbicide selection pressure are needed to mitigate the evolution of multiple-herbicide resistance in C. difformis of California rice.

Herbicidal Activity of Penoxsulam And Bispyribac-Sodium and its Combination With Mineral Oil And Spreading Material on Weed Rice Plant

Two field experiments were carried out at the Experimental Farm of Rice Research and Training Center(RRTC), Sakha, Kafr El-sheikh, Egypt, during 2009 and 2010 rice growing seasons. to study the effect of certain postemergenceherbicides (Penoxsulam and Bispyribac-sodium and their mixtures with mineral oil KZ and spreadingmaterial (Top film) on weeds control rice plant compared with non-chemical control Weedy check, The results Theresult showed that the number of tiller to Echinochloa crus-galli , Echinochloa colonum , Cyperus difformis. In alltested treatment from the results the most lesser above of weeds and highest percent reduction of weeds was found inpenoxsulam and bispyribac-sodium at the recommended rate of each herbicides wean the half rate both compounds wascompared one litter of spreading material or one litter of mineral oil was slightly increased of weeds with the higherincrease of percent reduction in total weeds compared with the effect of the half rate only of each tested compound.penoxsulam 2.5% half rate + 1000ml spreading material which gives 82%, 87%,83% and 84%,92%,88% during2009and 2010 season respectively. bispyribac-sodium 2% half rate + 1000ml spreading material which gives89%,89%,89% and 88%, 94%, 87% reduction in the total number, Also gave the most highest percent reduction in totaldry weight of weeds. When the mineral oil and spreading material were used with half recommended rate of the twoabove herbicides the percent reduction of dry weight of weed were approximately equal to the recommended rate ofeach tested herbicides such effect relieved to the efficacy of mineral oil and spreading material to improve the power ofhalf rate to reach the effect of recommended rate.

Factors affecting Cyperus difformis seed germination and seedling emergence

Specific knowledge about the dormancy, germination, and emergence patterns of weed species aids the development of integrated management strategies. Laboratory studies were conducted to determine the effect of several environmental factors on seed germination and seedling emergence of Cyperus difformis. Germination of freshly harvested seeds was inhibited by darkness; however, when seeds were subsequently transferred to complete light they germinated readily. Our results showed that 2 wk of cold stratification overcome the light requirement for germination. Seeds of C. difformis were able to germinate over a broad range of temperatures (25/15, 30/20, 35/25, and 40/30 ºC day/night). The response of germination rate to temperature was described as a non-linear function. Based on model outputs, the base, the optimum and the ceiling temperatures were estimated as 14.81, 37.72 and 45 ºC, respectively. A temperature of 120 ºC for a 5 min was required to inhibit 50% of maximum germination. The osmotic potential and salinity required for 50% inhibition of maximum germination were -0.47 MPa and 135.57 mM, respectively. High percentage of seed germination (89%) was observed at pH=6 and decreased to 12% at alkaline medium (pH 9) pH. Seeds sown on the soil surface gave the greatest percentage of seedling emergence, and no seedlings emerged from seeds buried in soil at depths of 1 cm.

Spatial distribution of nutsedge (Cyperus spp. L.) seed bank in rice growth cycle using geostatistics

A field experiment was conducted to investigate the spatial distribution of nutsedge (Cyperus spp L.) seed bank in rice growth cycle using geostatistics in 2010–11. The sampling from seed banks were performed prior to rice farm preparation and after rice harvest; also weeds density was determined in three different dates during the growing season. The results showed that the highest amount of weed population was belonging to nutsedge (Cyperus spp. L.) including Cyperus difformis, C. rotundus and C. esculentus species. Nugget/sill ratios for all variogram models ranged from 15.2 to 46.9%, indicated that there was strong and moderate spatial correlation as spherical and exponential variograms models between weed and seedling nutsedge at all stages of sampling. Visual assessments of the weed growth in these field indicated that the weed exist in patches, but mapping results showed that the size and morphology of these patches varied within field. In the present study, seed bank patchy pattern was roughly in accordance with seedling germination pattern. Generally the provided seed bank maps can be used not only as information database of seedling germination, but also for predicting of seed bank dynamics and weed management programs.