Emerging challenges and opportunities for education and research in weed science
- Chauhan, Bhagirath, Matloob, Amar, Mahajan, Gulshan, Aslam, Farhena, Florentine, Singarayer, Jha, Prashant
- Authors: Chauhan, Bhagirath , Matloob, Amar , Mahajan, Gulshan , Aslam, Farhena , Florentine, Singarayer , Jha, Prashant
- Date: 2017
- Type: Text , Journal article
- Relation: Frontiers in Plant Science Vol. 8, no. (2017), p. 1-13
- Full Text:
- Reviewed:
- Description: In modern agriculture, with more emphasis on high input systems, weed problems are likely to increase and become more complex. With heightened awareness of adverse effects of herbicide residues on human health and environment and the evolution of herbicide-resistant weed biotypes, a significant focus within weed science has now shifted to the development of eco-friendly technologies with reduced reliance on herbicides. Further, with the large-scale adoption of herbicide-resistant crops, and uncertain climatic optima under climate change, the problems for weed science have become multi-faceted. To handle these complex weed problems, a holistic line of action with multi-disciplinary approaches is required, including adjustments to technology, management practices, and legislation. Improved knowledge of weed ecology, biology, genetics, and molecular biology is essential for developing sustainable weed control practices. Additionally, judicious use of advanced technologies, such as site-specific weed management systems and decision support modeling, will play a significant role in reducing costs associated with weed control. Further, effective linkages between farmers and weed researchers will be necessary to facilitate the adoption of technological developments. To meet these challenges, priorities in research need to be determined and the education system for weed science needs to be reoriented. In respect of the latter imperative, closer collaboration between weed scientists and other disciplines can help in defining and solving the complex weed management challenges of the 21st century. This consensus will provide more versatile and diverse approaches to innovative teaching and training practices, which will be needed to prepare future weed science graduates who are capable of handling the anticipated challenges of weed science facing in contemporary agriculture. To build this capacity, mobilizing additional funding for both weed research and weed management education is essential. © 2017 Chauhan, Matloob, Mahajan, Aslam, Florentine and Jha.
- Authors: Chauhan, Bhagirath , Matloob, Amar , Mahajan, Gulshan , Aslam, Farhena , Florentine, Singarayer , Jha, Prashant
- Date: 2017
- Type: Text , Journal article
- Relation: Frontiers in Plant Science Vol. 8, no. (2017), p. 1-13
- Full Text:
- Reviewed:
- Description: In modern agriculture, with more emphasis on high input systems, weed problems are likely to increase and become more complex. With heightened awareness of adverse effects of herbicide residues on human health and environment and the evolution of herbicide-resistant weed biotypes, a significant focus within weed science has now shifted to the development of eco-friendly technologies with reduced reliance on herbicides. Further, with the large-scale adoption of herbicide-resistant crops, and uncertain climatic optima under climate change, the problems for weed science have become multi-faceted. To handle these complex weed problems, a holistic line of action with multi-disciplinary approaches is required, including adjustments to technology, management practices, and legislation. Improved knowledge of weed ecology, biology, genetics, and molecular biology is essential for developing sustainable weed control practices. Additionally, judicious use of advanced technologies, such as site-specific weed management systems and decision support modeling, will play a significant role in reducing costs associated with weed control. Further, effective linkages between farmers and weed researchers will be necessary to facilitate the adoption of technological developments. To meet these challenges, priorities in research need to be determined and the education system for weed science needs to be reoriented. In respect of the latter imperative, closer collaboration between weed scientists and other disciplines can help in defining and solving the complex weed management challenges of the 21st century. This consensus will provide more versatile and diverse approaches to innovative teaching and training practices, which will be needed to prepare future weed science graduates who are capable of handling the anticipated challenges of weed science facing in contemporary agriculture. To build this capacity, mobilizing additional funding for both weed research and weed management education is essential. © 2017 Chauhan, Matloob, Mahajan, Aslam, Florentine and Jha.
Germination biology of three populations of Navua sedge (Cyperus aromaticus)
- Chadha, Aakansha, Florentine, Singarayer, Dhileepan, Kunjithapatham, Dowling, Kim, Turville, Christopher
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Dowling, Kim , Turville, Christopher
- Date: 2021
- Type: Text , Journal article
- Relation: Weed Science Vol. 69, no. 1 (2021), p. 69-81
- Full Text: false
- Reviewed:
- Description: Navua sedge [Cyperus aromaticus (Ridley) Mattf. & Kük.] is an aggressive perennial sedge native to equatorial Africa that has become problematic in many Pacific islands and wet, tropical Queensland, Australia. It has had a significant impact on the livestock-grazing industry, sugarcane (Saccharum officinarum L.) and banana (Musa acuminata Colla) plantations, and various other ecosystems. A laboratory-based research investigation was conducted to understand germination and emergence requirements under various environmental conditions of three geographically varied populations sourced from South Johnstone (SJ), Mackay (M) and Nyleta Creek (NC) in Queensland. Germination was identified to be stimulated by light, with no germination recorded under darkness. Populations SJ and NC had optimal germination at alternating temperatures of 25/15, 30/20, and 35/25 C, whereas population M had optimal germination at 25/15 and 30/20 C. All populations recorded greater than 85% germination at all pH levels tested. Seeds of population SJ were more sensitive to salinity compared with populations M and NC, with SJ showing no germination at 100 mM, whereas populations M and NC had 23% and 9% germination, respectively. An inverse relationship was observed between osmotic potential and germination, with no germination recorded at osmotic potentials below -0.8 MPa in any population, indicating moisture availability is a critical requirement for germination. Exposing seeds to 120 C radiant heat completely inhibited germination in populations M and NC, whereas 3% of population SJ germinated following a 180-s exposure at 120 C. Seedling emergence decreased as planting depth increased. Emergence was greatest for seeds on the soil surface or at 0.5-cm burial depth, consistent with germination being stimulated by light. Knowledge of these biological characteristics of C. aromaticus seed germination will assist in investigation of suitable control actions for this species, particularly in the early stage of its invasion into new areas, and will contribute to significant reduction in the soil seedbank. © 2021 Cambridge University Press. All rights reserved.
Ecology and management of a tropical invasive weed, Cyperus aromaticus (Navua sedge) in Queensland, Australia
- Authors: Chadha, Aakansha
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: Cyperus aromaticus (Ridley) Mattf. & Kükenth, commonly known as Navua sedge is an invasive C4 perennial sedge species of the Cyperaceae family found predominantly in tropical environments. A native of tropical Africa, it has spread widely and become problematic in many southwest Pacific islands and in tropical north Queensland, Australia. It is a principal weed infesting pastures, sugarcane, banana and root crops, which causes significant damage across a range of industries including dairy, beef, sugarcane and banana in the highly fertile and productive areas of Queensland. The primary objective of this thesis was to contribute to a significant weed management problem at a stage where intervention is cost effective, efficient and environmentally sensitive. At the centre of this work, was a contribution to fundamental knowledge regarding the ecology of the species. The first objective was to examine the global literature on rhizomatous weeds and C. aromaticus in particular to identify the research problems and knowledge gaps. As C. aromaticus has dual mode of reproduction, via seeds and rhizomes, both these aspects were taken into consideration in the experimental chapters. The project critically addressed the issues related to (i) understanding the fundamental ecological aspects of reproduction via seeds in C. aromaticus, (ii) the regeneration of C. aromaticus from its rhizomes, and (iii) control of C. aromaticus using herbicides. A stepwise approach, involving multiple objectives was used to meet the primary objective of this project. Three experiments were conducted to understand the fundamental ecological aspects of reproduction via seeds. (i) A study was conducted to understand the soil seed bank dynamics of pastures invaded by C. aromaticus. It was found that C. aromaticus is the dominant species in the soil seed bank of pastures invaded by C. aromaticus and can contribute between 62% and 95% of the total seed bank. In this respect, the abundance of C. aromaticus seed in the soil seed bank is positively correlated with the aboveground biomass of C. aromaticus and 83% of the total C. aromaticus seeds was found in the top 0-5 cm layer of soil. (ii) The lifespan of C. aromaticus seeds was estimated by artificial ageing technique in the laboratory whereby the results indicate that long-term management is required to control the recruitment from the soil seed bank even in the absence of additional seed deposition. (iii) Seed germination ecology was investigated to understand the effect of various environmental factors on the germination of C. aromaticus seeds. It was found that light is absolutely required for C. aromaticus seed germination, and there was no germination of seeds above 150 mM NaCl concentration and -0.8 Mpa osmotic potential, or from seeds buried greater than 2 cm below the soil surface. Focussing on the regeneration from C. aromaticus rhizomes, an experiment was conducted to investigate the effect of rhizome size and burial depth on the emergence from rhizomes in different soil types. A positive correlation was found between the total emergence of tillers and rhizome fragment size of C. aromaticus, but a negative correlation was found between the total emergence of tillers and burial depth of rhizomes. Importantly, it was also found that rhizomes when reduced to 10 cm or smaller fragments and buried 15 cm or deeper will prevent emergence. A further two glasshouse experiments were conducted to explore chemical options to control both the aboveground biomass and the belowground rhizomes. (i) The herbicide sensitivity of various rates of halosulfuron-methyl was evaluated at different growth stages using plants with and without established rhizomes. Mortality of 27.5%, 0% and 5% was recorded when treated with 75 g ai ha-1 of halosulfuron-methyl at the mowed, pre-flowering and flowering stages, respectively in plants with established rhizomes. The herbicide was effective in controlling the aboveground growth, however, subsequent emergence of new growth from the rhizome confirms the failure of the herbicide to kill the rhizome. In contrast, application of 75 g ai ha-1 of halosulfuron-methyl provided 100% mortality in plants treated at seedling and pre-flowering stage in plants without established rhizomes. (ii) Another herbicide with an alternate mode of action, florpyrauxifen-benzyl, was assessed at different growth stages again using plants with and without established rhizomes. Results indicate that a single application of florpyrauxifen-benzyl is effective at controlling C. aromaticus seedlings, but not effective at controlling plants with established rhizomes. In summary, this thesis has increased the fundamental knowledge about the ecology of C. aromaticus which will feed into designing of management strategies. Likewise, new tools established in the form of mechanical and chemical control and improving the methods currently used to manage populations will advance the capacity to effectively manage C. aromaticus in the future. Although this investigation is based on a relatively focussed suite of issues relevant to tropical north Queensland, where there is an immediate application of the research outcomes from this study, it is anticipated that they will also inform weed management strategies more broadly in a range of similar environments throughout the world.
- Description: Doctor of Philosophy
- Authors: Chadha, Aakansha
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: Cyperus aromaticus (Ridley) Mattf. & Kükenth, commonly known as Navua sedge is an invasive C4 perennial sedge species of the Cyperaceae family found predominantly in tropical environments. A native of tropical Africa, it has spread widely and become problematic in many southwest Pacific islands and in tropical north Queensland, Australia. It is a principal weed infesting pastures, sugarcane, banana and root crops, which causes significant damage across a range of industries including dairy, beef, sugarcane and banana in the highly fertile and productive areas of Queensland. The primary objective of this thesis was to contribute to a significant weed management problem at a stage where intervention is cost effective, efficient and environmentally sensitive. At the centre of this work, was a contribution to fundamental knowledge regarding the ecology of the species. The first objective was to examine the global literature on rhizomatous weeds and C. aromaticus in particular to identify the research problems and knowledge gaps. As C. aromaticus has dual mode of reproduction, via seeds and rhizomes, both these aspects were taken into consideration in the experimental chapters. The project critically addressed the issues related to (i) understanding the fundamental ecological aspects of reproduction via seeds in C. aromaticus, (ii) the regeneration of C. aromaticus from its rhizomes, and (iii) control of C. aromaticus using herbicides. A stepwise approach, involving multiple objectives was used to meet the primary objective of this project. Three experiments were conducted to understand the fundamental ecological aspects of reproduction via seeds. (i) A study was conducted to understand the soil seed bank dynamics of pastures invaded by C. aromaticus. It was found that C. aromaticus is the dominant species in the soil seed bank of pastures invaded by C. aromaticus and can contribute between 62% and 95% of the total seed bank. In this respect, the abundance of C. aromaticus seed in the soil seed bank is positively correlated with the aboveground biomass of C. aromaticus and 83% of the total C. aromaticus seeds was found in the top 0-5 cm layer of soil. (ii) The lifespan of C. aromaticus seeds was estimated by artificial ageing technique in the laboratory whereby the results indicate that long-term management is required to control the recruitment from the soil seed bank even in the absence of additional seed deposition. (iii) Seed germination ecology was investigated to understand the effect of various environmental factors on the germination of C. aromaticus seeds. It was found that light is absolutely required for C. aromaticus seed germination, and there was no germination of seeds above 150 mM NaCl concentration and -0.8 Mpa osmotic potential, or from seeds buried greater than 2 cm below the soil surface. Focussing on the regeneration from C. aromaticus rhizomes, an experiment was conducted to investigate the effect of rhizome size and burial depth on the emergence from rhizomes in different soil types. A positive correlation was found between the total emergence of tillers and rhizome fragment size of C. aromaticus, but a negative correlation was found between the total emergence of tillers and burial depth of rhizomes. Importantly, it was also found that rhizomes when reduced to 10 cm or smaller fragments and buried 15 cm or deeper will prevent emergence. A further two glasshouse experiments were conducted to explore chemical options to control both the aboveground biomass and the belowground rhizomes. (i) The herbicide sensitivity of various rates of halosulfuron-methyl was evaluated at different growth stages using plants with and without established rhizomes. Mortality of 27.5%, 0% and 5% was recorded when treated with 75 g ai ha-1 of halosulfuron-methyl at the mowed, pre-flowering and flowering stages, respectively in plants with established rhizomes. The herbicide was effective in controlling the aboveground growth, however, subsequent emergence of new growth from the rhizome confirms the failure of the herbicide to kill the rhizome. In contrast, application of 75 g ai ha-1 of halosulfuron-methyl provided 100% mortality in plants treated at seedling and pre-flowering stage in plants without established rhizomes. (ii) Another herbicide with an alternate mode of action, florpyrauxifen-benzyl, was assessed at different growth stages again using plants with and without established rhizomes. Results indicate that a single application of florpyrauxifen-benzyl is effective at controlling C. aromaticus seedlings, but not effective at controlling plants with established rhizomes. In summary, this thesis has increased the fundamental knowledge about the ecology of C. aromaticus which will feed into designing of management strategies. Likewise, new tools established in the form of mechanical and chemical control and improving the methods currently used to manage populations will advance the capacity to effectively manage C. aromaticus in the future. Although this investigation is based on a relatively focussed suite of issues relevant to tropical north Queensland, where there is an immediate application of the research outcomes from this study, it is anticipated that they will also inform weed management strategies more broadly in a range of similar environments throughout the world.
- Description: Doctor of Philosophy
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