- Chadha, Aakansha, Florentine, Singarayer, Chauhan, Bhagirath, Long, Benjamin, Jayasundera, Mithila, Javaid, Muhammad, Turville, Christopher
- Authors: Chadha, Aakansha , Florentine, Singarayer , Chauhan, Bhagirath , Long, Benjamin , Jayasundera, Mithila , Javaid, Muhammad , Turville, Christopher
- Date: 2019
- Type: Text , Journal article
- Relation: Crop and Pasture Science Vol. 70, no. 8 (2019), p. 709-717
- Full Text: false
- Reviewed:
- Description: Wild lettuce (Lactuca serriola L.) is a significant emerging agricultural and environmental weed in many countries. This invasive species is now naturalised in Australia and is claimed to cause significant losses within the agricultural industry. Sustainable management of wild lettuce has been hampered by a lack of detailed knowledge of its seed ecology. Laboratory-based studies were performed to examine the potential influence of environmental factors including temperature and light conditions, salinity, pH, moisture availability and burial depth on the germination and emergence of two spatially distant populations of wild lettuce. Results suggested that the germination of wild lettuce seeds occurred across a broad range of temperature conditions (12-h cycle: 30°C/20°C, 25°C/15°C and 17°C/7°C) for both populations. We also found that these seeds are non-photoblastic germination was not affected by darkness, with >80% germination in darkness for both populations at all tested temperature ranges. Germination significantly declined as salinity and osmotic stress increased for both populations, with seeds from the Tempy population were more affected by NaCl >100 mM than seeds from Werribee, but in neither population was there any observed effect of pH on germination (>80% germination in both populations at all tested pH ranges). For both populations, germination significantly decreased as burial depth increased however, the two populations differed with regard to response to burial depth treatment, whereby seeds from the Tempy population had higher emergence than those from Werribee at 0.5 cm burial depth. These results suggest that light-reducing management techniques such as mulching or use of crop residues will be unsuccessful for preventing germination of wild lettuce. By contrast, burial of seeds at a depth of at least 4 cm will significantly reduce their emergence.
Influence of soil moisture regimes on growth, photosynthetic capacity, leaf biochemistry and reproductive capabilities of the invasive agronomic weed; Lactuca serriola
- Chadha, Aakansha, Florentine, Singarayer, Chauhan, Bhagirath, Long, Benjamin, Jayasundera, Mithila
- Authors: Chadha, Aakansha , Florentine, Singarayer , Chauhan, Bhagirath , Long, Benjamin , Jayasundera, Mithila
- Date: 2019
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 14, no. 6 (2019), p. 1-17
- Full Text:
- Reviewed:
- Description: Global temperatures are predicted to increase by 1.5–5.9C during this century, and this change is likely to impact average rainfall, with predictions that water deficit will perhaps be the most severe threat to sustainable agriculture. In this respect, invasive weeds, which have traits better adapted to drought stress than crops, add to concerns regarding crop sustainability. Lactuca serriola, an aggressive agronomic weed is thought to be a successful weed because of its ability to maintain high water use efficiency under drought conditions. In this study, experiments were conducted to examine the influence of different soil moisture regimes (100%, 75%, 50% and 25% water holding capacity (WHC)) on growth, photosynthetic capacity, leaf biochemistry and reproduction of this species. Soil moisture significantly affected plant’s height, stem diameter, number of leaves and biomass. The highest plant height (115.14 cm ± 11.64), shoot diameter (9.4 mm ± 0.18), leaf area (1206.5 mm2 ± 73.29), plant fresh weight (83.1 ± 3.98) and dry weight (22.38 ± 1.24) were recorded at 75% soil moisture content. A fundamental adaptation to drought was observed as plants in the 25% WHC treatment had the highest root: shoot ratio. Soluble sugars and total phenolic content were highest in the 25% WHC treatment and significantly different to 100% WHC which was a response to soil moisture stress to ameliorate the damaging effects of reactive oxygen species produced under stress conditions. Results also indicate that L. serriola can survive and produce seeds under water stress as more than 6000 seeds were produced per plant in all WHC treatments. In this study, there was no significant difference in the seed weight, number of seeds produced and their germination ability. This can have a huge impact on agricultural systems as the species can survive both under low and high soil moisture conditions. We therefore suggest that the demonstrated ability of L. serriola to complete its life cycle and produce biomass and seeds under water stressed conditions leads to the introduction of strategies that minimize weed survival while maximizing irrigation efficiency for the crop. A clear understanding of the ecological and biological characteristics of this weed will help land managers take appropriate control measures to mitigate the effect of this species on economic crop productivity.
- Authors: Chadha, Aakansha , Florentine, Singarayer , Chauhan, Bhagirath , Long, Benjamin , Jayasundera, Mithila
- Date: 2019
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 14, no. 6 (2019), p. 1-17
- Full Text:
- Reviewed:
- Description: Global temperatures are predicted to increase by 1.5–5.9C during this century, and this change is likely to impact average rainfall, with predictions that water deficit will perhaps be the most severe threat to sustainable agriculture. In this respect, invasive weeds, which have traits better adapted to drought stress than crops, add to concerns regarding crop sustainability. Lactuca serriola, an aggressive agronomic weed is thought to be a successful weed because of its ability to maintain high water use efficiency under drought conditions. In this study, experiments were conducted to examine the influence of different soil moisture regimes (100%, 75%, 50% and 25% water holding capacity (WHC)) on growth, photosynthetic capacity, leaf biochemistry and reproduction of this species. Soil moisture significantly affected plant’s height, stem diameter, number of leaves and biomass. The highest plant height (115.14 cm ± 11.64), shoot diameter (9.4 mm ± 0.18), leaf area (1206.5 mm2 ± 73.29), plant fresh weight (83.1 ± 3.98) and dry weight (22.38 ± 1.24) were recorded at 75% soil moisture content. A fundamental adaptation to drought was observed as plants in the 25% WHC treatment had the highest root: shoot ratio. Soluble sugars and total phenolic content were highest in the 25% WHC treatment and significantly different to 100% WHC which was a response to soil moisture stress to ameliorate the damaging effects of reactive oxygen species produced under stress conditions. Results also indicate that L. serriola can survive and produce seeds under water stress as more than 6000 seeds were produced per plant in all WHC treatments. In this study, there was no significant difference in the seed weight, number of seeds produced and their germination ability. This can have a huge impact on agricultural systems as the species can survive both under low and high soil moisture conditions. We therefore suggest that the demonstrated ability of L. serriola to complete its life cycle and produce biomass and seeds under water stressed conditions leads to the introduction of strategies that minimize weed survival while maximizing irrigation efficiency for the crop. A clear understanding of the ecological and biological characteristics of this weed will help land managers take appropriate control measures to mitigate the effect of this species on economic crop productivity.
Influence of elements of climate change on the growth and fecundity of Datura stramonium
- Chadha, Aakansha, Florentine, Singarayer, Javaid, Muhammad, Welgama, Amali, Turville, Christopher
- Authors: Chadha, Aakansha , Florentine, Singarayer , Javaid, Muhammad , Welgama, Amali , Turville, Christopher
- Date: 2020
- Type: Text , Journal article
- Relation: Environmental Science and Pollution Research Vol. 27, no. 28 (2020), p. 35859-35869
- Full Text: false
- Reviewed:
- Description: In this study, the performance of Datura stramonium, an invasive weed of soybean and solanaceous crops, was examined under different elements of climate change. Experiments conducted in CO2 chambers at ambient CO2 (400 ppm) and elevated CO2 (700 ppm) levels under both well-watered and drought conditions exhibited the fertilization effect of elevated CO2. This was, however, limited by drought. Clearly, growth of D. stramonium will be significantly enhanced by enriched atmospheric CO2 concentration under well-watered conditions, producing taller plants with greater biomass and higher seed output. Glasshouse experiments were conducted to evaluate the effect of different soil moisture regimes (100%, 75%, 50% and 25% water-holding capacity (WHC)) on the growth and fecundity of D. stramonium. Plants grown in 75% WHC had the highest plant height (15.24 cm) and shoot diameter (4.25 mm). The lowest leaf area (305.91 mm2), fresh weight (14.48 g) and dry weight (4.45 g) were observed in 25% WHC conditions. The ability of D. stramonium plants to grow and complete their life cycle with high seed output, even under limited water availability, shows the weedy nature of this species which is well adapted to survive future inhospitable climatic conditions. Radiant heat treatment on the plants indicated that temperatures of 120 °C and above for more than 180 s were enough to kill the plants, suggesting that thermal weeding or wildfires will be adequate to act as a circuit breaker on the D. stramonium invasion cycle, thus allowing other control measures to be engaged for greater control. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
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.
Amaranthus retroflexus L (redroot pigweed) : effects of elevated CO2 and soil moisture on growth and biomass and the effect of radiant heat on seed germination
- Weller, Sandra, Florentine, Singarayer, Welgama, Amali, Chadha, Aakansha, Turville, Christopher
- Authors: Weller, Sandra , Florentine, Singarayer , Welgama, Amali , Chadha, Aakansha , Turville, Christopher
- Date: 2021
- Type: Text , Journal article
- Relation: Agronomy Vol. 11, no. 4 (2021), p.
- Full Text:
- Reviewed:
- Description: Amaranthus retroflexus L. (Amaranthaceae), Redroot pigweed, is native to North America, but has become a weed of agriculture worldwide. Previous research into competition with food crops found it significantly reduces yields. Additionally, taxonomy, biomass allocation, physiological responses to light intensity, water stress, elevated CO2, and herbicide resistance have been inves-tigated. To extend other research findings, we investigated growth and biomass yield in response to (i) soil moisture stress, and (ii) drought and elevated CO2. Additionally, we investigated seed germination rates following exposure to three elevated temperatures for two different time periods. Overall, moisture stress reduced plant height, stem diameter, and number of leaves. Elevated CO2 (700 ppm) appeared to reduce negative impacts of drought on biomass productivity. Heating seeds at 120◦C and above for either 180 or 300 s significantly reduced germination rate. These results inform an understanding of potential responses of A. retroflexus to future climate change and will be used to predict future occurrence of this weed. The finding that exposing seeds to high temperatures retards germination suggests fire could be used to prevent seed germination from soil seed banks, particularly in no-till situations, and therefore may be used to address infestations or prevent further spread of this weed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliates “Sandra Weller, Singarayer Florentine, Amali Welgama, Aakansha Chadha, Chrisopher Turville" are provided in this record**
- Authors: Weller, Sandra , Florentine, Singarayer , Welgama, Amali , Chadha, Aakansha , Turville, Christopher
- Date: 2021
- Type: Text , Journal article
- Relation: Agronomy Vol. 11, no. 4 (2021), p.
- Full Text:
- Reviewed:
- Description: Amaranthus retroflexus L. (Amaranthaceae), Redroot pigweed, is native to North America, but has become a weed of agriculture worldwide. Previous research into competition with food crops found it significantly reduces yields. Additionally, taxonomy, biomass allocation, physiological responses to light intensity, water stress, elevated CO2, and herbicide resistance have been inves-tigated. To extend other research findings, we investigated growth and biomass yield in response to (i) soil moisture stress, and (ii) drought and elevated CO2. Additionally, we investigated seed germination rates following exposure to three elevated temperatures for two different time periods. Overall, moisture stress reduced plant height, stem diameter, and number of leaves. Elevated CO2 (700 ppm) appeared to reduce negative impacts of drought on biomass productivity. Heating seeds at 120◦C and above for either 180 or 300 s significantly reduced germination rate. These results inform an understanding of potential responses of A. retroflexus to future climate change and will be used to predict future occurrence of this weed. The finding that exposing seeds to high temperatures retards germination suggests fire could be used to prevent seed germination from soil seed banks, particularly in no-till situations, and therefore may be used to address infestations or prevent further spread of this weed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliates “Sandra Weller, Singarayer Florentine, Amali Welgama, Aakansha Chadha, Chrisopher Turville" are provided in this record**
Biology, ecology, distribution and control of the invasive weed, lactuca serriola l. (wild lettuce) : a global review
- Chadha, Aakansha, Florentine, Singarayer
- Authors: Chadha, Aakansha , Florentine, Singarayer
- Date: 2021
- Type: Text , Journal article , Review
- Relation: Plants Vol. 10, no. 10 (2021), p.
- Full Text:
- Reviewed:
- Description: Lactuca serriola L. (wild lettuce) is a highly invasive C3 weed in many countries, including Australia, Canada, and the USA. This weed is a severe threat to agricultural systems, especially in crops grown with reduced or no‐tillage approaches, which commonly include wheat, cereals and pulses. Owing to the vertical orientation of its leaves in the north‐south plane and its root architec-ture, L. serriola can maintain high water use efficiency under drought conditions, giving it the ability to expand its range under a drying climate. Each plant can produce up to 100,000 seeds which have no primary dormancy and form a short‐term seedbank lasting up to three years. Most seedlings emerge in autumn and overwinter as a rosette, with a small flush of emergence in spring depicting staggered germination. Research into control methods for this weed has been performed, and these methods include chemical herbicides applied alone and in combination, the establishment of plant competition, tillage, mowing and bioherbicide. Herbicides can provide effective control when applied in the seedling or rosette stage; however, spring germination is difficult to control, as it skips the rosette stage. Some biotypes are now resistant to ALS inhibitor and synthetic auxins, causing concern regarding using herbicides. A dedicated integrated management plan for 3–4 years is recommended for the control of this troublesome species. This review will explore the biology, ecology, distribution, current control techniques and previous research on this weed, allowing us to make recommendations for its future research and management. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- Authors: Chadha, Aakansha , Florentine, Singarayer
- Date: 2021
- Type: Text , Journal article , Review
- Relation: Plants Vol. 10, no. 10 (2021), p.
- Full Text:
- Reviewed:
- Description: Lactuca serriola L. (wild lettuce) is a highly invasive C3 weed in many countries, including Australia, Canada, and the USA. This weed is a severe threat to agricultural systems, especially in crops grown with reduced or no‐tillage approaches, which commonly include wheat, cereals and pulses. Owing to the vertical orientation of its leaves in the north‐south plane and its root architec-ture, L. serriola can maintain high water use efficiency under drought conditions, giving it the ability to expand its range under a drying climate. Each plant can produce up to 100,000 seeds which have no primary dormancy and form a short‐term seedbank lasting up to three years. Most seedlings emerge in autumn and overwinter as a rosette, with a small flush of emergence in spring depicting staggered germination. Research into control methods for this weed has been performed, and these methods include chemical herbicides applied alone and in combination, the establishment of plant competition, tillage, mowing and bioherbicide. Herbicides can provide effective control when applied in the seedling or rosette stage; however, spring germination is difficult to control, as it skips the rosette stage. Some biotypes are now resistant to ALS inhibitor and synthetic auxins, causing concern regarding using herbicides. A dedicated integrated management plan for 3–4 years is recommended for the control of this troublesome species. This review will explore the biology, ecology, distribution, current control techniques and previous research on this weed, allowing us to make recommendations for its future research and management. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Biology, ecology and management of the invasive navua sedge (cyperus aromaticus) : a global review
- Shi, Boyang, Osunkoya, Olusegun, Chadha, Aakansha, Florentine, Singarayer, Dhileepan, Kunjithapatham
- Authors: Shi, Boyang , Osunkoya, Olusegun , Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham
- Date: 2021
- Type: Text , Journal article , Review
- Relation: Plants Vol. 10, no. 9 (2021), p.
- Full Text:
- Reviewed:
- Description: Navua sedge (Cyperus aromaticus (Ridley) Mattf. & Kukenth) is an invasive perennial sedge, native to tropical Africa, which is threatening many natural ecosystems and agroecosystems, especially in northern Queensland, Australia. Crop and pasture production have been impacted by Navua sedge and it is also directly causing reductions in dairy and beef production in affected regions. This review documents the biology, ecology and potential management options to minimise the spread and impact of Navua sedge. The weed reproduces both sexually (seeds) and vegetatively (via underground rhizomes). Its tiny seeds can be spread easily via wind, water, vehicles, farm machinery and animals, whilst the rhizomes assist with establishment of dense stands. The CLIMEX model (which uses distribution and climate data in native and novel ranges) indicates that in Australia, Navua sedge has the potential to spread further within Queensland and into the Northern Territory, New South Wales and Victoria. Several management strategies, including mechanical, chemical and agronomic methods, and their integration will have to be used to minimise agricultural production losses caused by Navua sedge, but most of these methods are currently either ineffective or uneconomical when used alone. Other management approaches, including biological control and mycoherbicides, are currently being explored. We conclude that a better understanding of the interaction of its physiological processes, ecological patterns and genetic diversity across a range of conditions found in the invaded and native habitats will help to contribute to and provide more effective integrated management approaches for Navua sedge. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- Authors: Shi, Boyang , Osunkoya, Olusegun , Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham
- Date: 2021
- Type: Text , Journal article , Review
- Relation: Plants Vol. 10, no. 9 (2021), p.
- Full Text:
- Reviewed:
- Description: Navua sedge (Cyperus aromaticus (Ridley) Mattf. & Kukenth) is an invasive perennial sedge, native to tropical Africa, which is threatening many natural ecosystems and agroecosystems, especially in northern Queensland, Australia. Crop and pasture production have been impacted by Navua sedge and it is also directly causing reductions in dairy and beef production in affected regions. This review documents the biology, ecology and potential management options to minimise the spread and impact of Navua sedge. The weed reproduces both sexually (seeds) and vegetatively (via underground rhizomes). Its tiny seeds can be spread easily via wind, water, vehicles, farm machinery and animals, whilst the rhizomes assist with establishment of dense stands. The CLIMEX model (which uses distribution and climate data in native and novel ranges) indicates that in Australia, Navua sedge has the potential to spread further within Queensland and into the Northern Territory, New South Wales and Victoria. Several management strategies, including mechanical, chemical and agronomic methods, and their integration will have to be used to minimise agricultural production losses caused by Navua sedge, but most of these methods are currently either ineffective or uneconomical when used alone. Other management approaches, including biological control and mycoherbicides, are currently being explored. We conclude that a better understanding of the interaction of its physiological processes, ecological patterns and genetic diversity across a range of conditions found in the invaded and native habitats will help to contribute to and provide more effective integrated management approaches for Navua sedge. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- Chadha, Aakansha, Florentine, Singarayer, Dhileepan, Kunjithapatham, Turville, Christopher, Dowling, Kim
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Turville, Christopher , Dowling, Kim
- Date: 2022
- Type: Text , Journal article
- Relation: Weed Technology Vol. 36, no. 3 (2022), p. 397-402
- Full Text: false
- Reviewed:
- Description: Navua sedge is a creeping perennial sedge commonly found in tropical environments and is currently threatening many agroecosystems and ecosystems in Pacific Island countries and northern Queensland, Australia. Pasture and crop productions have been significantly impacted by this weed. The efficacy of halosulfuron-methyl on Navua sedge plants with and without well-established rhizomes was evaluated under glasshouse conditions. Halosulfuron-methyl was applied to plants with established rhizomes at three stages; mowed, pre-flowering, and flowering growth stages, whereas plants without established rhizomes were treated at seedling, pre-flowering and flowering growth stages. At each application time, halosulfuron-methyl was applied at four dose rates of 0, 38, 75, and 150 g ai ha-1. Mortality of 27.5%, 0%, and 5% was recorded in rhizomatous Navua sedge when treated with 75 g ai ha-1 of halosulfuron-methyl at the mowed, pre-flowering stage and flowering stages, respectively. At 10 wk after treatment (WAT), there were no tillers in surviving plants treated at any of the application times. By 16 WAT, the number of tillers increased to 15, 24, and 26 in mowed, pre-flowering, and flowering stages, respectively. Although halosulfuron-methyl is effective in controlling aboveground growth, subsequent emergence of new growth from the rhizome confirms the failure of the herbicide to kill the rhizome. Application of 75 g ai ha-1 of halosulfuron-methyl provided 100% mortality in plants treated at seedling and pre-flowering stages, and 98% mortality when treated at flowering stage in non-rhizomatous plants. A single application of halosulfuron-methyl is highly effective at controlling Navua sedge seedlings but not effective at controlling plants with established rhizomes. © 2022 Cambridge University Press. All rights reserved.
Evaluation of Florpyrauxifen-Benzyl for the control of Cyperus aromaticus (Navua sedge)
- Chadha, Aakansha, Florentine, Singarayer, Dhileepan, Kunjithapatham, Turville, Chris, Dowling, Kim
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Turville, Chris , Dowling, Kim
- Date: 2022
- Type: Text , Journal article
- Relation: Advances in Weed Science Vol. 40, no. (2022), p.
- Full Text:
- Reviewed:
- Description: Background: Cyperus aromaticus (Navua sedge) is a creeping perennial sedge common to tropical environments, currently threatening many agroecosystems and ecosystems in Pacific Island countries and northern Queensland in Australia. Objective: A glasshouse study was conducted to evaluate the efficacy of florpyrauxifen-benzyl on C. aromaticus plants with and without established rhizomes. Methods: The plants with established rhizomes were treated at three application times being mowed, pre-flowering and flowering growth stages and plants without established rhizomes were treated at seedling, pre-flowering and flowering growth stages. At each application time, plants were treated with four rates of florpyrauxifen-benzyl: 0, 15, 30 and 60 g a.i. ha-1 and control. Results: There was no mortality in the plants with established rhizomes. Reduction in the number of tillers was observed at four weeks after treatment (WAT) in plants treated with 30 and 60 g a.i. ha-1 of herbicide, however, there was new growth from the rhizomes and the number of tillers increased at 8 WAT. Conversely, florpyrauxifen-benzyl provided above 95% control in plants without established rhizomes. Conclusions: These results indicate florpyrauxifen-benzyl can help manage a new C. aromaticus infestation prior to the establishment of rhizomes. However, it has little to no impact on C. aromaticus plants with established rhizomes, and other management options should be employed to control them. © 2022, Sociedade Brasileira da Ciencia das Plantas Daninha. All rights reserved.
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Turville, Chris , Dowling, Kim
- Date: 2022
- Type: Text , Journal article
- Relation: Advances in Weed Science Vol. 40, no. (2022), p.
- Full Text:
- Reviewed:
- Description: Background: Cyperus aromaticus (Navua sedge) is a creeping perennial sedge common to tropical environments, currently threatening many agroecosystems and ecosystems in Pacific Island countries and northern Queensland in Australia. Objective: A glasshouse study was conducted to evaluate the efficacy of florpyrauxifen-benzyl on C. aromaticus plants with and without established rhizomes. Methods: The plants with established rhizomes were treated at three application times being mowed, pre-flowering and flowering growth stages and plants without established rhizomes were treated at seedling, pre-flowering and flowering growth stages. At each application time, plants were treated with four rates of florpyrauxifen-benzyl: 0, 15, 30 and 60 g a.i. ha-1 and control. Results: There was no mortality in the plants with established rhizomes. Reduction in the number of tillers was observed at four weeks after treatment (WAT) in plants treated with 30 and 60 g a.i. ha-1 of herbicide, however, there was new growth from the rhizomes and the number of tillers increased at 8 WAT. Conversely, florpyrauxifen-benzyl provided above 95% control in plants without established rhizomes. Conclusions: These results indicate florpyrauxifen-benzyl can help manage a new C. aromaticus infestation prior to the establishment of rhizomes. However, it has little to no impact on C. aromaticus plants with established rhizomes, and other management options should be employed to control them. © 2022, Sociedade Brasileira da Ciencia das Plantas Daninha. All rights reserved.
Soil seed bank dynamics of pastures invaded by navua sedge (cyperus aromaticus) in tropical north Queensland
- Chadha, Aakansha, Osunkoya, Olusegun, Shi, Boyang, Florentine, Singarayer, Dhileepan, Kunjithapatham
- Authors: Chadha, Aakansha , Osunkoya, Olusegun , Shi, Boyang , Florentine, Singarayer , Dhileepan, Kunjithapatham
- Date: 2022
- Type: Journal article
- Relation: Frontiers in agronomy Vol. 4, no. (2022), p.
- Full Text:
- Reviewed:
- Description: Navua sedge (Cyperus aromaticus) is threatening crops, pasture species and natural ecosystems in Pacific Island countries and northern Queensland, Australia. To aid future management efforts of this exotic invasive weed, research was conducted to understand the soil seed bank dynamics of pastures invaded by Navua sedge. Six grazing properties were chosen across two landscapes, coastal and inland/upland, with areas that had Navua sedge infestations in Queensland, Australia. At each site, soil was collected from two soil depths, 0-5 and 5-10 cm, and from plots with high and low infestation levels of Navua sedge. It was observed that the soil seed bank dynamics varied significantly between these study sites. Navua sedge was the dominant species in the soil seed bank at all the sites contributing between 62% to 95% of the total seed bank, while pasture seeds occupied only 3% to 24%. Broadleaf seeds were even lower in abundance, showing between 2% to 13% of the total seed count. The abundance of Navua sedge seed present in the soil was significantly correlated with the aboveground biomass of Navua sedge (r=0.53, p=0.006), but no correlation was found with the infestation age of Navua sedge. Based on this work, it is clear that the seed bank of Navua sedge is very large and concentrated within the top 0-5 cm of the soil, with, 83% of total Navua sedge seeds being in this layer. It was also noted that, although, high infestation plots had significantly higher number of seeds than low infestation plots, more than 18,000 Navua sedge seeds/m 2 were still found in the 0-5 cm soil layer of plots regarded as low infestation. We suggest that insights achieved from our soil seed bank study may be used to devise management strategies to minimise the impact of Navua sedge weed in critical grazing and agricultural areas.
- Authors: Chadha, Aakansha , Osunkoya, Olusegun , Shi, Boyang , Florentine, Singarayer , Dhileepan, Kunjithapatham
- Date: 2022
- Type: Journal article
- Relation: Frontiers in agronomy Vol. 4, no. (2022), p.
- Full Text:
- Reviewed:
- Description: Navua sedge (Cyperus aromaticus) is threatening crops, pasture species and natural ecosystems in Pacific Island countries and northern Queensland, Australia. To aid future management efforts of this exotic invasive weed, research was conducted to understand the soil seed bank dynamics of pastures invaded by Navua sedge. Six grazing properties were chosen across two landscapes, coastal and inland/upland, with areas that had Navua sedge infestations in Queensland, Australia. At each site, soil was collected from two soil depths, 0-5 and 5-10 cm, and from plots with high and low infestation levels of Navua sedge. It was observed that the soil seed bank dynamics varied significantly between these study sites. Navua sedge was the dominant species in the soil seed bank at all the sites contributing between 62% to 95% of the total seed bank, while pasture seeds occupied only 3% to 24%. Broadleaf seeds were even lower in abundance, showing between 2% to 13% of the total seed count. The abundance of Navua sedge seed present in the soil was significantly correlated with the aboveground biomass of Navua sedge (r=0.53, p=0.006), but no correlation was found with the infestation age of Navua sedge. Based on this work, it is clear that the seed bank of Navua sedge is very large and concentrated within the top 0-5 cm of the soil, with, 83% of total Navua sedge seeds being in this layer. It was also noted that, although, high infestation plots had significantly higher number of seeds than low infestation plots, more than 18,000 Navua sedge seeds/m 2 were still found in the 0-5 cm soil layer of plots regarded as low infestation. We suggest that insights achieved from our soil seed bank study may be used to devise management strategies to minimise the impact of Navua sedge weed in critical grazing and agricultural areas.
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
Effect of Rhizome Fragment Length and Burial Depth on the emergence of a tropical invasive Weed Cyperus aromaticus (Navua Sedge)
- Chadha, Aakansha, Florentine, Singarayer, Dhileepan, Kunjithapatham, Turville, Christopher
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Turville, Christopher
- Date: 2022
- Type: Text , Journal article
- Relation: Plants Vol. 11, no. 23 (2022), p.
- Full Text:
- Reviewed:
- Description: Cyperus aromaticus (Navua sedge) is a problematic perennial weed in pastures and crops including sugarcane, banana, rice, and fruits and vegetables in tropical climates. It reproduces both via rhizomes and seeds. As a regenerative and storage organ, these rhizomes play an important part in the invasion, establishment, and persistence of this weed. To eliminate their regenerative ability, it is important to understand the regrowth potential with respect to rhizome fragment size and burial depth. This study evaluated the emergence of C. aromaticus from rhizomes in a controlled condition. Three different sizes of rhizome fragments were buried at seven depths of up to 20 cm in two soil types. The experimental measurements included (i) the time for tillers to emerge, (ii) the cumulative emergence of tillers, recorded weekly, and (iii) the number of underground emerging tillers. The cumulative shoot emergence and the number of underground tillers produced were found to be positively correlated with the initial length of the rhizome fragments and negatively correlated with the burial depth. The time for the emergence of the tillers was negatively correlated with the burial depth, and soil type had no significant effect on any of the parameters recorded. There was no emergence recorded from rhizomes buried at 15 cm depth and deeper, irrespective of their size. Our results indicate that the combination of the fragmentation of rhizomes into small pieces and a deep burial, below 15 cm, is an important aspect to control the regeneration of C. aromaticus from rhizomes, if tillage is carried out, and can therefore form a part of an integrated weed management strategy for this troublesome weed. © 2022 by the authors.
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Turville, Christopher
- Date: 2022
- Type: Text , Journal article
- Relation: Plants Vol. 11, no. 23 (2022), p.
- Full Text:
- Reviewed:
- Description: Cyperus aromaticus (Navua sedge) is a problematic perennial weed in pastures and crops including sugarcane, banana, rice, and fruits and vegetables in tropical climates. It reproduces both via rhizomes and seeds. As a regenerative and storage organ, these rhizomes play an important part in the invasion, establishment, and persistence of this weed. To eliminate their regenerative ability, it is important to understand the regrowth potential with respect to rhizome fragment size and burial depth. This study evaluated the emergence of C. aromaticus from rhizomes in a controlled condition. Three different sizes of rhizome fragments were buried at seven depths of up to 20 cm in two soil types. The experimental measurements included (i) the time for tillers to emerge, (ii) the cumulative emergence of tillers, recorded weekly, and (iii) the number of underground emerging tillers. The cumulative shoot emergence and the number of underground tillers produced were found to be positively correlated with the initial length of the rhizome fragments and negatively correlated with the burial depth. The time for the emergence of the tillers was negatively correlated with the burial depth, and soil type had no significant effect on any of the parameters recorded. There was no emergence recorded from rhizomes buried at 15 cm depth and deeper, irrespective of their size. Our results indicate that the combination of the fragmentation of rhizomes into small pieces and a deep burial, below 15 cm, is an important aspect to control the regeneration of C. aromaticus from rhizomes, if tillage is carried out, and can therefore form a part of an integrated weed management strategy for this troublesome weed. © 2022 by the authors.
Assessing seed longevity of the Invasive Weed Navua Sedge (Cyperus aromaticus), by artificial ageing
- Chadha, Aakansha, Florentine, Singarayer, Dhileepan, Kunjithapatham, Turville, Christopher
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Turville, Christopher
- Date: 2022
- Type: Text , Journal article
- Relation: Plants Vol. 11, no. 24 (2022), p.
- Full Text:
- Reviewed:
- Description: Navua sedge (Cyperus aromaticus (Ridley) Mattf. & Kukenth) is a significant agricultural and environmental weed found in tropical island countries including north Queensland, Australia. It is a prolific seed producer and consequently forms a high-density seedbank, and therefore understanding the longevity and persistence of the seeds can provide critical information required for the management of this species. A laboratory-controlled artificial ageing experiment was conducted where the seeds were exposed to a temperature of 45 °C and 60% relative humidity for 125 days. Seeds were removed at various times (1, 2, 5, 9, 20, 30, 50, 75, 100 and 125 days) and their viability determined through standard germination tests. It took 20 days in the artificial ageing environment for the seeds to decline to 50% viability which indicates that Navua sedge has relatively short-lived persistent seeds. These findings will assist in developing a better understanding of the seedbank dynamics of this invasive species, allowing managers to tactically implement control strategies and prepare budgets for ongoing treatments, and have implications for the duration and success of management programs. © 2022 by the authors.
Assessing seed longevity of the Invasive Weed Navua Sedge (Cyperus aromaticus), by artificial ageing
- Authors: Chadha, Aakansha , Florentine, Singarayer , Dhileepan, Kunjithapatham , Turville, Christopher
- Date: 2022
- Type: Text , Journal article
- Relation: Plants Vol. 11, no. 24 (2022), p.
- Full Text:
- Reviewed:
- Description: Navua sedge (Cyperus aromaticus (Ridley) Mattf. & Kukenth) is a significant agricultural and environmental weed found in tropical island countries including north Queensland, Australia. It is a prolific seed producer and consequently forms a high-density seedbank, and therefore understanding the longevity and persistence of the seeds can provide critical information required for the management of this species. A laboratory-controlled artificial ageing experiment was conducted where the seeds were exposed to a temperature of 45 °C and 60% relative humidity for 125 days. Seeds were removed at various times (1, 2, 5, 9, 20, 30, 50, 75, 100 and 125 days) and their viability determined through standard germination tests. It took 20 days in the artificial ageing environment for the seeds to decline to 50% viability which indicates that Navua sedge has relatively short-lived persistent seeds. These findings will assist in developing a better understanding of the seedbank dynamics of this invasive species, allowing managers to tactically implement control strategies and prepare budgets for ongoing treatments, and have implications for the duration and success of management programs. © 2022 by the authors.
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