Weedy Rice Control Research Articles

MANAGEMENT OF RED RICE (ORYZA SATIVA) AND BARNYARDGRASS (ECHINOCHLOA CRUS-GALLI) GROWN WITH SORGHUM WITH REDUCED RATE OF ATRAZINE AND MECHANICAL METHODS

SUMMARYThe weedy variety ofOryza sativaoccurs in several rice cultivation areas reducing both grain yield and quality. Prevention and crop rotation are considered the basic means to reduce its presence. Weed control in sorghum is generally attained with atrazine. In this study, the efficacy of both chemical and mechanical methods for control, under different soil tillage conditions, of weedy rice and barnyardgrass during sorghum cultivation was evaluated with the aim to reduce the application rate of atrazine. In the case of chemical control, the atrazine rate (1000, 1500, 2000, 2500 and 3000 ga.i.ha−1) and application timing (pre- and post-emergence) were assessed. With the mechanical control method, the number of interventions (inter-row hoeing with sorghum at 3, 4–5 and 6–8 leaves) to avoid weed competition was determined. The effect of the tillage system on weed population was investigated comparing conventional (ploughing), minimum-tillage (disc harrowing) and sod seeding (no-tillage) in combination with pre- and post-emergence herbicide treatments. The results showed that efficient control of weedy rice and barnyardgrass was achieved in lowlands with sorghum in rotation with rice. Both chemical and mechanical methods of weed control in sorghum gave a level of efficiency higher than 60%. The application of atrazine was more efficient in pre-emergence application, rather than in post-emergence treatments, in all soil tillage systems tested. On both weed species, the most suitable application rate was the pre-emergence treatment with 1500 ga.i.ha−1, and the adoption of higher rates did not significantly increase the herbicidal efficacy. The adoption of two or three mechanical interventions resulted in sorghum yield higher than the chemical post-emergence application, and similar to the application of atrazine in pre-emergence. Higher yield results were in accordance to greater weed control, being obtained in the conventional tillage system.

Germination of Weedy Rice in Response to Field Conditions during Winter

Weedy rice is a problematic weed that infests paddy fields worldwide. Differing populations, with varying physiological and morphological traits, characterize this weed. In particular, seed dormancy makes its control difficult. The objective of this study was to evaluate the germination behavior of five Italian weedy rice populations (two awnless, two awned, and one mucronate) after exposure of seeds to different field storage conditions (flooding, burial, and dry soil surface) during winter in two sites (Grugliasco and Vercelli, Italy). Seed samples were taken from each population, storage condition, and site, every 15 d for petri dish germinability testing. The two sites displayed slightly different germination patterns, which were probably due to the differing climatic conditions. One of the awned populations showed the highest (always exceeding 80%) and fastest germination percentage in all field conditions and sites, compared with the other four populations. Although flooding promoted germination in one awnless population, it delayed germination in two others (one awned and one awnless), attaining only 20% germination after more than 100 d. In all populations, burial delayed germination, whereas seed placement on the dry soil surface enhanced it. Our study indicated that autumn tillage that promotes weedy rice seed burial should be discouraged; spring tillage that exposes seeds to the soil surface and cause their depletion should be encouraged. The tested technique of winter flooding can also improve weedy rice control, despite its varying efficacy among populations. Cycles of flooding and drying followed by spring tillage might improve weedy rice seed control.

Weed Control of Weedy Red Rice among Cultivated Rice in Nagano Prefecture (Second Report)

Weed Control of Weedy Red Rice among Cultivated Rice in Nagano Prefecture (Second Report)

Effects of winter flooding on weedy rice ( Oryza sativa L.)

Weedy rice ( Oryza sativa L.), characterised by competitiveness, seed longevity, and dormancy is a troublesome weed to rice fields. Furthermore, its close botanical affinity to cultivated rice makes its control particularly difficult. However, winter flooding of rice fields can be an efficient technique to control weedy rice infestation by promoting weed seed decay, animal predation, or germination. The effects of winter flooding on weedy rice plant and seed densities were assessed via two methods: field study of plant densities and laboratory study of germination behaviour. In the field experiment, weedy rice plant density decreased following application of winter flooding. In fact, winter flooding resulted in more than a 95% reduction in the number of viable weedy rice seeds on the soil surface as compared to reductions in the range of 26–77% on fields left dry between rice crops. The laboratory study showed that weedy rice germinability was affected by storage duration, moisture condition, and thermal regimen. In general, seed germinability increased with storage duration. Both awnless and awned populations displayed poor germinability under low temperature seed storage, but displayed differences when moisture content varied. At −20 °C, we observed, on average, 58% of seeds to be non-viable when stored for 248 days in water. At +5 °C the awnless population showed higher germination percentages following shorter storage durations, particularly water stored seeds. At +25 °C, the highest germination values were recorded in both populations after dry storage, whereas in water, total germination of the awnless population was inversely related to storage duration. Under typical field temperatures, in dry conditions germination behaviour was intermediate between that displayed at +5 °C and +25 °C, while storage in water resulted in a faster dormancy breaking in both populations. The results suggest that winter flooding can be a useful practice to mitigate weedy rice infestations as it promotes germination already in the autumn, before rigorous winter conditions, and favours the decay of non-germinated seeds under low temperature conditions.

Diversity of plant traits of weedy rice in Liaoning and Jiangsu provinces

Liaoning and Jiangsu are main regions seriously infested by weedy rice (Oryza sativa f. spontanea ) in China. Weedy rice samples collected from 29 sites in 14 cities of the two provinces were cultivated in Nanjing, and 23 traits during vegetative and reproductive growth stage were observed and measured in order to reveal the diversity and identification traits of weedy rice. The results showed that there were differences of traits in terms of plant height after one month, tiller number after one month or two months during vegetative stage, and in terms of pericarp color, grain length/width ratio, 100-seed weight, shattering habit, culm rigidity, flag leaf width, flag leaf length, yellow maturity, half-yellow maturity–half-heading, full yellow maturity during reproductive stage between weedy rice and cultivated rice in the two provinces. The scatter plot of the first and second principlal components (their cumulative contribution accounting for 43.24%) also showed that there were differences between Liaoning and Jiangsu weedy rice, as well as between weedy and cultivated rice of the two provinces. Cluster analysis based on Euclidean distance showed that weedy rice populations could be divided into two types: Japonica-like and Indica-like weedy rice. Liaoning weedy rice populations fall into first category. Jiangsu weedy rice populations fall into both categories. Weedy rice of the two provinces can be further divided into 6 classes: (I) the Japonica-like type with strong shattering, light grain weight, short stem and prematurity; (II) the Japonica-like type with no awn, many panicle, late maturity, narrow flag leave and strong dormancy; (III) the Japonica-like type with long awn, weak tillering, few pancle and weak shattering; (IV) the Indica-like type with hard culm, wide flag 30 生 物 多 样 性 Biodiversity Science 第 18 卷 leave, late maturity and strong dormancy; (V) the Indica-like type with red pericarp, long grain, soft culm, and heavy grain weight; (VI) the Indica-like type with no awn, tall stem, long flag leave and long panicle. The study on the morphological index and classification of weedy rice in the two provinces may provide theoretical basis for prevention and control of weedy rice.

Polymorphisms in the ALS gene of weedy rice ( Oryza sativa L.) accessions with differential tolerance to imazethapyr

Herbicide-resistant Clearfield™ rice technology allows the use of ALS inhibitors to control weedy rice. Weedy rice plants have differential tolerance to imazethapyr, perhaps due to ALS polymorphisms. We aimed to assess ALS polymorphisms in weedy rice accessions from Arkansas, USA, with differential tolerance to imazethapyr in seedling growth bioassays. Six base changes were identified in the ALS of 14 weedy rice accessions. Three of these nucleotide changes resulted in amino acid substitutions — Pro 93Thr, Glu 630Asp, and Val 669Met — in four accessions: Ark-4, Ark-9, Poi-1 and Poi-6. The GR 50 values and inhibition of root and shoot growth (%) of these accessions differed. The Glu 630Asp substitution occurs in the herbicide binding domain B and Val 669Met occurs at the C-terminal tail where the co-factor binds. Variability in weedy rice ALS exists, but polymorphism patterns did not relate to tolerance levels. The observed mutations presented the possibility that sustained selection pressure will eventually lead to selection of a herbicide-tolerant individual that will be the progenitor of a resistant population. Concomitantly, pollen-mediated gene flow from Clearfield™ rice to weedy rice will lead to the evolution of ALS-resistant weedy rice populations.

A strategy to provide long‐term control of weedy rice while mitigating herbicide resistance transgene flow, and its potential use for other crops with related weeds

Transgenic herbicide-resistant rice is needed to control weeds that have evolved herbicide resistance, as well as for the weedy (feral, red) rice problem, which has been exacerbated by shifting to direct seeding throughout the world-firstly in Europe and the Americas, and now in Asia, as well as in parts of Africa. Transplanting had been the major method of weedy rice control. Experience with imidazolinone-resistant rice shows that gene flow to weedy rice is rapid, negating the utility of the technology. Transgenic technologies are available that can contain herbicide resistance within the crop (cleistogamy, male sterility, targeting to chloroplast genome, etc.), but such technologies are leaky. Mitigation technologies tandemly couple (genetically link) the gene of choice (herbicide resistance) with mitigation genes that are neutral or good for the crop, but render hybrids with weedy rice and their offspring unfit to compete. Mitigation genes confer traits such as non-shattering, dwarfism, no secondary dormancy and herbicide sensitivity. It is proposed to use glyphosate and glufosinate resistances separately as genes of choice, and glufosinate, glyphosate and bentazone susceptibilities as mitigating genes, with a six-season rotation where each stage kills transgenic crop volunteers and transgenic crop x weed hybrids from the previous season.

Preliminary assessment of the effect of water-seeding technique and herbicide application on weedy rice tillers

Metsulfuron methyl has been recommended to control weedy rice under wetseeded conditions (Zainal and Azmi, unpubl. data, 1994). Another weed control method involves broadcasting pregerminated seeds using the water-seeding technique. This study was undertaken to evaluate the effect of seeding methods and herbicide application on weedy rice tillers 45 d after sowing (DAS). A factorial experiment was carried out in a glasshouse at Putra University Malaysia. Treatment 1 (T1) was the wet-seeding method—broadcasting seed on saturated soil and introducing water up to 10-cm flooding depth 7 d after seeding with (H1) and without herbicide (H0). Treatment 2 (T2) was water seeding—continuous flooding at 10-cm depth from seeding to date of data collection with H1 and H0. All treatments were replicated five times and arranged in a factorial randomized complete block design. Both weedy rice seeds and pregerminated MR219 seeds were sown on the soil surface (Tropic Fluvaquent) into 25.5-cm-diameter × 40-cm-high experimental containers using the MARDI-recommended seed rate (500 seeds m–2) (MARDI 2004) to achieve uniform establishment. Herbicide (metsulfuron methyl 1.75% combined with bensulfuron methyl 8.25%) was applied 14 DAS at 0.05 kg ai ha–1. Water was brought in 7 DAS for treatments with herbicide (T1) to facilitate herbicide application. The effects of water seeding and herbicide application on tillering ability of weedy rice (45 DAS) were analyzed using ANOVA. The means of these treatments were compared using Duncan’s new multiple range test. Only the seeding method was significantly different at P ≤0.05. There were no significant effects or interactions for the other sources of variation tested (see table). Weedy rice tillers decreased in both seeding methods (see figure).

Competitive N uptake between rice and weedy rice

Weedy rice, red rice ( Oryza sativa L.), is a serious problem in rice-producing areas of the southern U.S. and various regions worldwide. It competes for production inputs, increases weed control cost, reduces yield and grain quality, and could eliminate economic returns. Research was conducted to compare: (i) the relative efficiencies of rice and weedy rice in recovering fertilizer N under a competitive condition, (ii) the accumulation and partitioning of N by rice and weedy rice, and (iii) the N use efficiency of rice and weedy rice. Experiments were conducted in 1999 and 2000 at the Rice Research and Extension Center, Stuttgart, Arkansas, USA. Experimental units were arranged in a split–split plot design with N rate (0, 5, 10, 15, and 20 g m −2) as mainplot, plant type (rice and weedy rice) as subplot, and type of shoot tissue (lower leaf, leaf sheath, top leaf, and panicle) as the sub-subplot. ‘Drew’ rice and strawhull weedy rice were drill-seeded in alternate rows. At 26–27 days after planting, metal collars were driven into the soil to establish two microplots per treatment. Urea labeled with 15N was applied to dry soil in the microplots immediately before permanent flood. Data were collected at panicle initiation (PI) and 2 weeks after heading (WAH). Regardless of growth stage, Drew rice and weedy rice produced equivalent shoot biomass when no fertilizer N was added. At PI, both plant types showed a quadratic response to fertilizer N with respect to biomass production. However, where the response to N was positive, weedy rice accumulated 42 g shoot biomass g −1 of added N whereas shoot biomass accumulation for Drew was 33 g g −1 of added N. Overall, weedy rice accumulated more biomass than rice upon addition of N fertilizer. The difference in shoot biomass production between Drew and weedy rice became larger as the growing season progressed. At 2 WAH, weedy rice continued to produce more biomass at the highest N rate, but Drew did not respond substantially to added N. Weedy rice had more culm biomass (55% of total) than Drew (48%). Lower leaves constituted 16–19% of total shoot biomass, flag leaf 6%, and panicles comprised the rest for both plant types. In general, weedy rice accumulated more N, responded to higher N rates, accumulated more N in the panicles, and had a higher N use efficiency (for biomass production) than Drew rice. Weedy rice can accumulate 63% of fertilizer N, 2 WAH. We conclude that weedy rice responds to higher N rates, takes up more N, and has higher N use efficiency for biomass production than rice. Whenever a rice field is heavily infested with weedy rice, controlling weedy rice should be the priority. Otherwise, fertilizer N application (which is more expensive than weedy rice control) is not profitable.

Weed problems and their management in rice fields of Malaysia: An overview

The available literature on weed problems and weed control in rice fields in Malaysia is reviewed and suggestions for future research are included. The problem of weed competition with rice is of great economic importance in the country because it causes a 10–35% reduction in grain yield. About US$4.10 million is spent annually on herbicides for rice alone, and this amounts to approximately 7% of the total expenditure on herbicides. The shift in methods of rice culture from transplanting to direct seeding has magnified the weed problem. The problem of weedy rice is particularly acute in the direct‐seeding rice areas. Although a number of sulfonylurea herbicides (e.g. cinosulfuron, metsulfuron, bensulfuron and pyrazosulfuron) have been found to be suitable alternatives to the old herbicide 2,4‐D, an integrated weed management program must be developed in order to reduce the problem of herbicide resistance in weeds. Weed control methods that are more friendly to the environment and affordable to farmers must be sought. Weed‐competitive and allelopathic rice varieties must be produced. The problem of weeds in rice calls for systematic studies on biotechnological methods of control of weedy rice. Detailed studies on the biology and ecology of notorious rice weeds, particularly Oryza sativa L. (weedy rice), Echinochloa spp., Leptochloa chinensis (L.) Nees, Fimbristylis miliacea (L.) Vahl. and Limnocharis flava (L.) Buch. need to be done in order to formulate successful weed control measures.

Herbicide resistant rice (Oryza sativa L.): Global implications for weedy rice and weed management*

SummaryRice cultivars resistant to broad‐spectrum herbicides have been developed and their commercial release is imminent, especially for imidazolinone and glufosinate resistant varieties in the USA and Latin America. Glyphosate‐resistant rice should follow within a few years. Rice growers throughout the world could benefit from the introduction of herbicide‐resistant rice cultivars that would allow in‐crop, selective control of weedy Oryza species. Other perceived benefits are the possibility to control ‘hard‐to‐kill’ weed species and weed populations that have already evolved resistance to herbicides currently used in rice production, especially those of the Echinochloa species complex. Weed management could also be improved by more efficient post‐emergence control. Introduction of herbicide resistant rice could also bring areas heavily infested with weedy rice that have been abandoned back to rice production, allow longer term crop rotations, reduce consumption of fossil fuels, promote the replacement of traditional chemicals by more environmentally benign products, and provide more rice grain without adding new land to production. There are also concerns, however, about the impact of releasing herbicide‐resistant rice on weed problems. Of most concern is the possibility of rapid transfer of the resistance trait to compatible weedy Oryza species. Development of such herbicide resistant weedy rice populations would substantially limit the chemical weed management options for farmers. Herbicide‐resistant rice volunteers also could become problematic, and added selection pressure to weed populations could aggravate already serious weed resistance problems. Because of the risk of weedy Oryza species becoming resistant to broad‐spectrum herbicides, mitigating measures to prevent gene flow, eventually attainable by both conventional breeding and molecular genetics, have been proposed. With commercialisation of the first herbicide resistant varieties planned for 2001, these mitigating measures will not be available for use with this first generation of herbicide resistant rice products. Release of herbicide resistant rice should depend on a thorough risk assessment especially in areas infested with con‐specific weedy rice or intercrossing weedy Oryza species. Regulators will have to balance risks and benefits based on local needs and conditions before allowing commercialisation of herbicide‐resistant rice varieties. If accepted, these varieties should be considered as components of integrated weed management, and a rational herbicide use and weedy rice control should be promoted to prevent losing this novel tool.

水稲不耕起乾田直播栽培における雑草イネ防除法〜稲わら焼却・非選択性除草剤の播種後処理・DCMU水和剤散布・厚播きの検討〜

水稲不耕起乾田直播栽培における雑草イネ防除法〜稲わら焼却・非選択性除草剤の播種後処理・DCMU水和剤散布・厚播きの検討〜

Environmental Microbiology. W. D. Grant , P. E. Long

Previous articleNext article No AccessNew Biological BooksEnvironmental Microbiology. W. D. Grant , P. E. Long Tom FenchelTom Fenchel Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 57, Number 4Dec., 1982 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/412970 Views: 1Total views on this site Citations: 1Citations are reported from Crossref Copyright 1981 Stony Brook Foundation, Inc.PDF download Crossref reports the following articles citing this article:Youichi Ohdaira Effects and Utilization Techniques of Lime Nitrogen on Control of Volunteer Rice and Weedy Rice (Oryza sativa L.), Japanese Journal of Crop Science 90, no.22 (Apr 2021): 117–124.https://doi.org/10.1626/jcs.90.117