ORCID Profile
0000-0002-7231-9067
Current Organisation
University of Queensland - Gatton Campus
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Proteomics and Intermolecular Interactions (excl. Medical Proteomics) | Horticultural Production | Ecological Impacts of Climate Change | Horticultural Crop Growth and Development
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/RJ16021
Abstract: Cascabela thevetia (L.) Lippold is a garden ornamental in northern Australia and two biotypes, the peach and the yellow, are recognised. In some areas it has naturalised and now has environmental and economic effects. As part of a broader research program into the ecology of C. thevetia, a field study was undertaken in northern Queensland to quantify seed fall and seed predation (by avian wildlife) of the peach biotype. The amount of twigging caused by birds while they fed on the seeds and the level of litter production were also recorded. Seed fall, seed predation, twigging and litter production occurred in all months of the year. Seed fall increased slowly over late spring and summer before peaking in mid- to late autumn (April–May) and then declining until October. Mean (± s.e.m.) estimated total annual seed fall was 19140 ± 2880 and 17030 ± 2930 seeds ha–1 in the first and second years respectively. Seed predation by birds was substantial, with 57% of all seeds predated. Birds also chewed an average of 600 twigs ha–1 year–1. Litter production varied from 430 to 950 kg dry weight (DW) ha–1 month–1. In total, 7900 ± 640 and 7390 ± 1420 kg (DW) litter was produced during the first and second years respectively. Although seed production of C. thevetia is less than a lot of other rangeland weeds, seed predation by birds further reduces the number of seeds entering the soil seed bank. The stem damage that occurred in conjunction with seed predation contributed to overall litter production and warrants further investigation in terms of its effect on plant growth.
Publisher: MDPI AG
Date: 19-10-2021
Abstract: While there are many high profile Opuntioid cactus species invading rangeland environments in Australia, Cereus uruguayanus Ritt. ex Kiesl. has also naturalised and formed large and dense infestations at several locations. With no herbicides registered for control of C. uruguayanus in Australia, the primary aim of this study was to identify effective herbicides to control it using a range of techniques. This involved a large screening trial of twelve herbicides and four techniques, followed by a rate refinement trial for cut stump applications and another to test residual herbicides. Despite most treatments (except monosodium methylarsonate (MSMA)) taking a long time to kill plants, at least one effective herbicide was identified for basal bark (triclopyr icloram), cut stump (aminopyralid/metsulfuron-methyl, glyphosate, metsulfuron-methyl, triclopyr icloram, triclopyr icloram/aminopyralid), stem injection (glyphosate, MSMA, triclopyr icloram/aminopyralid) and foliar applications (aminopyralid/metsulfuron-methyl, MSMA, triclopyr, triclopyr icloram/aminopyralid) due to their ability to kill both small and large plants. Ground application of residual herbicides was less conclusive with neither hexazinone nor tebuthiuron causing adequate mortality at the rates applied. This study has identified effective herbicides for the control of C. uruguayanus using several techniques, but further research is needed to refine herbicide rates and develop integrated management strategies for a range of situations and infestation sizes and densities.
Publisher: MDPI AG
Date: 26-05-2023
Abstract: Pimelea trichostachya Lindl is a little-understood Australian native plant, with irregular field emergence, causing significant poisoning to grazing livestock. The study aims to examine the form of dormancy exhibited by P. trichostachya and determine how key environmental conditions, such as alternating temperature and light conditions, moisture availability, substrate pH and burial depth, affect its germination and emergence. The study concludes that P. trichostachya has a complex dormancy mechanism. This comprises a physical component that can be partly removed by fruit scarification, a metabolic dormancy that can be overcome by gibberellic acid (GA3), and a suspected third mechanism based on a water-soluble germination inhibitor. The results showed that scarified single seeded fruit (hereafter seed) with GA3 treatment gave the highest germination percentage (86 ± 3%) at 25/15 °C, with good germination rates at other temperature regimes. Light exposure stimulated germination, but a significant proportion of seeds still germinated in the dark. The study also found that seeds could germinate under water-limited conditions and a wide range of pH levels (4 to 8). Seedling emergence was inhibited when seeds were buried below 3 cm in soil. Pimelea trichostachya emergence in the field commonly occurs from Autumn to Spring. Understanding its dormancy mechanism and recognizing its triggers for germination will enable better prediction of outbreaks. This can help landholders prepare for emergence and help manage seedbank build-up in pastures and crops.
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/RJ13011
Abstract: Bellyache bush (Jatropha gossypiifolia L.) is an invasive weed that poses economic and environmental problems in northern Australia. Competition between pasture and bellyache bush was examined in North Queensland using combinations of five pasture treatments (uncut (control) cut as low, medium, and high pasture and no pasture) and four bellyache bush densities (0, 2, 6 and 12 plants m−2) in a buffel grass (Cenchrus ciliaris L.) dominated pasture. The pasture treatments were applied approximately once per year but no treatments were applied directly to the bellyache bush plants. Measurements of bellyache bush flowering, seed formation, and mortality were undertaken over a 9-year period, along with monitoring the pasture basal cover and plant species ersity. Maximum flowering rates of bellyache bush occurred after 9 years (97%) in plots containing no pasture, with the lowest rates of 9% in uncut control plots. Earliest flowering (322 days after planting) and seed formation (411 days) also occurred in plots with no pasture compared with all other pasture treatments (range 1314–1393 days for seed formation to occur). No seeds were produced in uncut plots. At the end of 9 years, mortality rates of bellyache bush plants initially planted averaged ≥73% for treatments with some pasture compared with 55% under the no-pasture treatment. The percentage of herbaceous plant basal cover in uncut plots was increased 5-fold after 9 years, much greater than the average 2% increase recorded across the low, medium, and high pasture treatments. The number of herbaceous species in uncut plots remained largely unchanged, whereas there was an average reduction of 46% in the cut pasture treatments. Buffel grass remained the species with the greatest basal cover across all cut pasture treatments, followed by sabi grass (Urochloa mosambicensis (Hack.) Dandy) and then red Natal grass (Melinis repens (Willd.) Ziska). These results suggest that grazing strategies that maintain a healthy and competitive pasture layer may contribute to reducing the rate of spread of bellyache bush and complement traditional control techniques such as the use of herbicides.
Publisher: MDPI AG
Date: 13-04-2023
DOI: 10.20944/PREPRINTS202304.0300.V1
Abstract: Low pasture biomass production and fodder scarcity are among the major challenges affecting productivity of dairy cattle farms in Sri Lanka. As a potential solution to this, two Napier hybrid cultivars CO-5 and S oorna were recently introduced and a field experiment was conducted to evaluate their growth, dry matter production and nutritional composition during May to September 2020. Plant measurements and s les were collected at five harvest intervals (4, 6, 8, 10 and 12 weeks after planting), with the plant s les subjected to biomass and nutritional assessments. The number of tillers and leaf length differed (P=0.01) between the two cultivars at 4 weeks harvesting interval (HI) whilst number of leaves differed at 12 HI respectively. Dry matter yield increased (P=0.16) almost linearly whilst crude protein declined exponentially with CO-5 greater than S oorna (P=0.057 9.3% vs 8.7%), with increasing harvesting intervals respectively. In-vitro Organic Matter Digestibility and In-vitro Metabolizable Energy contents were similar across weeks 4, 6 and 8 but then decreased. This study demonstrates that higher dry matter yields (12.54 t/ha) can be obtained by harvesting both cultivars at 12 HI, but from a nutritional perspective harvesting at 6 HI during Yala season of the year would be optimum for farmers.
Publisher: CSIRO Publishing
Date: 19-12-2022
DOI: 10.1071/RJ22022
Abstract: Cereus uruguayanus R.Kiesling is a naturalised, non-opuntioid cactus that has formed large and dense infestations at several locations in the northern Australian rangelands. Of the Cactoideae subfamily, it typically grows into a large, spiny, single- or multi-stemmed candelabra-shaped cactus. While not classified as a Weed of National Significance (WONS) in Australia, it is causing increasing concern, with some local governments declaring it under their local laws. Recent research has identified several herbicides that control C. uruguayanus by using a range of techniques, including basal-bark, cut-stump, foliar, and stem injection applications. Of these, stem injection is one of the recommended options where weeds grow among desirable vegetation because the risk of non-target damage is minimised. This study evaluated C. uruguayanus control using a range of encapsulated dry-formulation herbicides from BioHerbicides Australia (BHA Pty Ltd), using their novel stem-implantation system (Injecta®). In May 2018, an experiment was established in central Queensland to compare the efficacy of six encapsulated herbicides (aminopyralid + metsulfuron-methyl, clopyralid, glyphosate, hexazinone, metsulfuron-methyl, triclopyr + picloram) against an untreated control. Glyphosate was the fastest-acting herbicide, followed by aminopyralid + metsulfuron-methyl and metsulfuron-methyl, with triclopyr + picloram much slower to act. Nevertheless, all four herbicides eventually caused high mortality (≥85%). In contrast, clopyralid and hexazinone were ineffective at the applied rates. Future research is recommended to compare the cost effectiveness of this system against other techniques, particularly those used for stem-injection applications.
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/EA03194
Abstract: Understanding the dispersal of weed species is important for the development of effective control strategies. In this study, a series of experiments was conducted to clarify the role that meat ants (Iridomyrmex spadius) play in dispersing bellyache bush (Jatropha gossypiifolia), an exotic shrub currently invading the rangelands of northern Australia. The nutrient composition of food [lipids (fatty acids), fat and soluble carbohydrates] provided by bellyache bush seed components [caruncle, exotegmen and seed (without caruncle and exotegmen)] was identified. Seed components were rich in lipids, particularly palmitic, oleic, stearic, linoleic and eicosenic acids. Oleic and palmitic were most abundant in the caruncle (30% each), linoleic in the seed (61%) and palmitic in the exotegmen (36%). Over all seed components, fat concentration was relatively high (6.3%) compared with soluble carbohydrates (2.3%). The impact of feeding was then determined by comparing germination and viability of intact, non-carunculate (caruncle manually removed) and ant-discarded bellyache bush seeds. Feeding by meat ants significantly increased seed germinability, whilst having no adverse affects on viability. The quantity of seeds dispersed and the seasonal pattern of dispersal was recorded by collecting seed from the middens of randomly selected meat ant nests on a monthly basis. On average, 12 330 ± 603 seeds were retrieved from the middens of in idual meat ant nests over 12 months, with highest numbers recorded between February and June ( seeds/ant nest). The effect of this dispersal was determined through comparisons of plant densities within core infestations of bellyache bush, meat ant nest middens and pastures located directly adjacent to core infestations and that were being invaded primarily through localised ballistic dispersal. The density of bellyache bush plants growing from the seed reserves within middens averaged 79 plants/m2, just 18% less than that within core infestations. Seedling survival (1 year) and growth within core infestation and meat ant sites was also quantified. The middens of meat ant nests provided an environment conducive to higher seedling survival and faster growth rates than occurred within core infestations. Mutualistic interaction between bellyache bush and meat ants is likely to build local ‘infestation pressure’ that may be conducive to range extension in years of exceptionally wet seasons. Management of seed dispersal by meat ants may reduce that risk.
Publisher: MDPI AG
Date: 19-07-2023
Abstract: Low pasture biomass production and fodder scarcity are among the major challenges affecting productivity of dairy cattle farms in Sri Lanka. As a potential solution to this, two Napier hybrid cultivars, CO-5 and S oorna, were recently introduced, and a field experiment was conducted to evaluate their growth, dry matter production, and nutritional composition from May to September 2020 to identify the optimum stage of harvest during the Yala season of the year. Plant measurements and s les were collected at five harvest intervals (4, 6, 8, 10, and 12 weeks after planting, respectively), with the plant s les subjected to biomass and nutritional assessments. The number of tillers and leaf length significantly differed (p = 0.01) between the two cultivars at 4 weeks harvesting interval (HI), whilst the number of leaves differed at 12-week HI, respectively. Dry matter yield increased (p = 0.16) almost linearly, whilst crude protein declined exponentially with CO-5 greater than S oorna (p = 0.057 9.3% vs. 8.7%), with increasing harvesting intervals, respectively. In vitro organic matter digestibility and in vitro metabolizable energy contents were similar across weeks 4, 6, and 8 but then decreased. This study demonstrates that higher dry matter yields (12.54 t/ha) can be obtained through harvesting both cultivars at 12 week HIs, but from a nutritional perspective, harvesting at 6 week HIs during Yala season of the year would be optimum for farmers.
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/RJ13091
Abstract: Sticky florestina (Florestina tripteris DC.) is an annual exotic weed that has become naturalised near the townships of Tambo and Barcaldine in central western Queensland, Australia. Three experiments conducted near Barcaldine identified foliar herbicides effective in killing sticky florestina plants and in providing residual activity to reduce recruitment from the soil seed bank. An initial chemical screening experiment evaluated the efficacy of 28 herbicide treatments. The most promising herbicides were then further evaluated in two response-rate experiments. Overall, 2,4-D icloram, aminopyralid/fluroxypyr, clopyralid, metsulfuron-methyl and triclopyr icloram proved to be the most effective selective herbicides. Two of these, metsulfuron-methyl at 18 g active ingredient (a.i) ha–1 and 2,4-D + picloram at 900 g a.i. ha–1 + 225 g a.i. ha–1 have now been included in a minor use permit (PER11920) with the Australian Pesticides and Veterinary Medicines Authority (APVMA) for the control of sticky florestina in pasture, stock route, roadside and non-crop situations using both spot and boom-spray applications (APVMA 2010). The permit also allows the use of 2,4-D amine for the control of seedlings only.
Publisher: MDPI AG
Date: 08-09-2023
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/RJ04016
Abstract: Age-class frequency distributions are valuable means of describing plant populations because they can be used to infer population history. Variables other than age are also often used to describe plant populations, either because they more accurately reflect an attribute of interest, or because it is difficult to determine age. However, interpretation of frequency distributions based on variables other than age can be problematic. We discuss these problems and illustrate them using data from six populations of the invasive rangeland shrub Parkinsonia aculeata L. We used three different measures of plant size: height, canopy diameter and stem cross-sectional area. Structures based on these measures were compared with structures based on three different estimates of above-ground biomass derived from them. For each variable, structures differed greatly between populations, and for each population, they were strongly dependent on the variable used to describe it. Population structures based on three-dimensional variables (above-ground biomass) tend to be more strongly positively skewed than those based on two-dimensional (area) measures of plant size. These in turn are more strongly positively skewed than those based on one-dimensional (height, diameter) measures. The statistical basis of this general phenomenon is discussed. The results highlight the difficulties of deriving histories and projecting futures of populations from size-class frequency distributions without accompanying knowledge of the temporal patterns of change in size variables as plants grow.
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/RJ02011
Abstract: Parkinsonia aculeata is an invasive, introduced shrub that is found in all mainland states of Australia except Victoria. It is especially prevalent north of the tropic of Capricorn. Size-biomass relationships were established for this species using data from 167 shrubs spread across eight sites in the Northern Territory and north-eastern Queensland. Above-ground dry weight (W, kg) can be predicted from plant height (H, m), canopy diameter (D, m) or stem cross-sectional area (A, cm2) using the equations: W = 0.025 H4.47 W = 0.091 D3.64 W = 0.022 A1.61 These relationships are linear when plotted on log-log scales. Although there was a significant effect of "site" on the log-log relationships between above-ground dry weight and size variables, the amount of information lost by not using site-specific equations is relatively small. These results provide reliable methods for estimating above-ground biomass in this species, the most robust being based on measurements of stem diameter at 20 cm above ground level.
Publisher: American Geophysical Union (AGU)
Date: 10-2018
DOI: 10.1029/2018GC007562
Publisher: Centro Internacional de Agricultura Tropical
Date: 03-09-2019
Abstract: Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.Leucaena (Leucaena leucocephala) is widely recognized in many countries as a commercially valuable plant, particularly when used as a nutritious fodder in subtropical and tropical regions. However, it is also considered an environmental weed in some countries due to its ability to form dense infestations in disturbed areas, where it is not proactively managed or grazed. These different perspectives have made leucaena a contentious species. Ideally, landholders and relevant jurisdictions in charge of invasive species need to work together to minimize its spread as a weed and manage existing infestations. To date, the response has been varied, ranging from no action through to some jurisdictions formally recognizing leucaena as an environmental weed within relevant legislation and applying requirements to minimize its impact. Between these extremes, there are initiatives such as an industry Code of Practice (i.e. The Leucaena Network in Australia), recommending that those growing leucaena adhere to certain principles and practices to minimize the risk of spread from their operations. The biology of weed leucaena (e.g. large seed production, relatively long-lived seed banks) and the situations in which it spreads (e.g. roadsides and riparian systems) pose management challenges to landholders and relevant jurisdictions. Adaptive management and experimental research are necessary to identify effective control strategies for a range of situations.
Publisher: Wiley
Date: 23-07-2019
DOI: 10.1111/AEC.12776
Publisher: Wiley
Date: 28-11-2022
Abstract: Navua sedge ( Cyperus aromaticus ), a perennial monocot plant native to tropical Africa, is a major weed in pasture and cropping areas in the wet tropical regions of Australia and South Pacific countries. In grazing pasture lands, rapid growth and reproduction of unpalatable Navua sedge leads to displacement of co‐occurring pasture species and depletion of livestock carrying capacity and production. Understanding the interspecific competitive ability of Navua sedge with co‐occurring desirable grasses and in response to varying ecological scenarios (e.g., grazing and plant density) is critical for the management of the weed in pasture situations. In a glasshouse setting, two co‐occurring pasture species—humidicola ( Urochloa humidicola ) and Rhodes grass ( Chloris gayana ) were grown with Navua sedge, in pots using a replacement series model. For each Navua sedge weed–pasture species pair, the experimental setup comprised of four ratios in two densities under simulated grazing and nongrazing conditions of the pasture grasses. Navua sedge growth and reproduction was highest when it grew as a monoculture or when co‐occurring pastures were exposed to simulated grazing as this action, reduced the competitiveness of the pasture grasses. Overall and using biomass gained, tiller production and relative yield as indices of growth dynamics, Rhodes grass was more competitive against Navua sedge than humidicola in both grazed and nongrazed conditions especially under high plant density. These results suggest the potential to include competitive pastures in integrated management strategies for Navua sedge, but species selection and grazing practices may influence the effectiveness of this approach.
Publisher: MDPI AG
Date: 02-06-2023
Abstract: Pimelea is a genus of about 140 plant species, some of which are well-known for causing animal poisoning resulting in significant economic losses to the Australian livestock industry. The main poisonous species/subspecies include Pimelea simplex (subsp. simplex and subsp. continua), P. trichostachya and P. elongata (generally referred to as Pimelea). These plants contain a diterpenoid orthoester toxin, called simplexin. Pimelea poisoning is known to cause the death of cattle (Bos taurus and B. indicus) or weaken surviving animals. Pimelea species are well-adapted native plants, and their diaspores (single seeded fruits) possess variable degrees of dormancy. Hence, the diaspores do not generally germinate in the same recruitment event, which makes management difficult, necessitating the development of integrated management strategies based on infestation circumstances (e.g., size and density). For ex le, the integration of herbicides with physical control techniques, competitive pasture establishment and tactical grazing could be effective in some situations. However, such options have not been widely adopted at the field level to mitigate ongoing management challenges. This systematic review provides a valuable synthesis of the current knowledge on the biology, ecology, and management of poisonous Pimelea species with a focus on the Australian livestock industry while identifying potential avenues for future research.
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/EA01047
Abstract: This study compared the efficacy of first and second fires applied during the early (August–September) and late dry season (October–November) on mortality of riparian (climbing) and subriparian (freestanding) infestations of rubber vine (Cryptostegia grandiflora R. Br.). The impact of fire treatments on germinable seed banks of monocotyledonous and dicotyledonous species was also determined. In idually, fire season, habitat type and number of fires significantly affected mortality of rubber vine plants. Late-season fires promoted higher mortality of rubber vine (96%) than early season fires (77%), with rubber vine in subriparian habitats more susceptible (90% mortality) than that growing in riparian areas (68% mortality). On average, fire mortality increased from 32% after the first fire up to 86% following 2 fires. Sensitivity of juvenile, mature, and old rubber vine plants to fire was in the order of mature juvenile old. Early fires significantly reduced seed banks of monocotyledonous plants, particularly in riparian habitats. Late fires significantly reduced seed banks of both dicotyledonous and monocotyledonous plants. No rubber vine seeds were detected in the germinable seed bank of either burnt or unburnt plots.
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/RJ17025
Abstract: Cascabela thevetia (L.) Lippold (Apocynaceae), commonly known as Captain Cook tree or yellow oleander, has established large infestations in riparian areas along several creeks and rivers in northern Queensland. To better understand the ecology of C. thevetia and the implications for its spread and management, this study reports seven experiments related to the seed ecology of its yellow and peach biotypes. We quantified its germination response to ambient (Experiment 1a and 1b), alternating and constant temperature (Experiment 2a and 2b) regimes and exposure to different light conditions (Experiment 3). Seed longevity under two soil types, two levels of pasture cover and three burial depths was also determined (Experiment 4a and 4b). Both loose seeds and seeds still within pods (kernels) of the two biotypes of C. thevetia were able to germinate in all months of the year in northern Queensland, irrespective of the large differences in monthly ambient temperatures experienced at the Charters Towers study site. Both biotypes also germinated across a wide range of alternating day/night temperatures from 16/12°C to 47/37°C and constant temperatures from 17°C to 44.0°C. Germination of the two biotypes was significantly greater (4-fold) and faster (7 days earlier) under shade than under natural light conditions. Over all biotypes, soil types, levels of pasture cover and burial depths, no seeds of C. thevetia remained viable after 2 years: longevity was much less in many circumstances. The results demonstrate that C. thevetia seeds can germinate over a wide temperature range, whereas the ability of seed to remain viable at low temperatures highlights the potential for expansion of its current potential distribution towards southern latitudes of the Australian continent. Across all experimental conditions, the yellow biotype displayed superior seed germination and viability traits compared with the peach biotype. Seed banks of the peach and yellow biotypes of C. thevetia are short-lived (2 years), which may be exploited when developing management strategies to reduce its impacts.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/RJ20035
Abstract: Calotrope (Calotropis procera (Aiton) W.T. Aiton) is an exotic woody weed that has invaded northern Australia’s rangelands since being introduced in the early 1900s. To expand the range of control options beyond herbicide-based methods, we undertook a stem/root cutting experiment that helped quantify the potential for using mechanical control techniques. In idual, medium-sized (1.72±0.03m high) calotrope plants were cut off at ground level (0cm) or below ground (10 or 20cm) using either a pruning saw or mattock respectively. All calotrope plants cut at ground level reshot vigorously. After four months they had more than twice the number of stems (7.4±0.54) of the uncut control plants and by 12 months they were only 26cm shorter than the control plants. In contrast, all plants cut at 10 or 20cm below ground were killed. Some mortality also started occurring in the control and ground level (0cm) treatments after eight months, but appeared to be associated with a dieback phenomenon. Nevertheless, the results demonstrate the potential to use equipment that severs the root system below ground, such as blade ploughs and cutter bars. A subsequent stick raking demonstration achieved moderate plant mortality (72%) after 13 months, yet produced a six-fold increase in original plant density as a result of new seedling emergence. This finding supports the view that mechanical disturbance will often promote seedling recruitment, and land managers need to have the capacity to undertake follow-up control practices to avoid exacerbating the problem.
Publisher: CSIRO Publishing
Date: 2000
DOI: 10.1071/EA00032
Abstract: Studies were undertaken at 2 sites in northern Queensland (Wrotham Park and Ten Mile Creek) to quantify the effects of fire on germination and viability of both loose rubber vine seeds and seeds held within pods. Seed lots were placed at a range of positions within the vertical profile of rubber vine infestations 0.5 cm below ground (loose seeds only), on bare ground, below fuel, above fuel and on crowns of free-standing rubber vine. The influence of seed age (0 and 1 year old) and seed plumage (with and without plumes) was also examined for loosely held seeds. Late season fires were imposed at both Wrotham Park and Ten Mile Creek, with an additional early season fire undertaken at Ten Mile Creek to enable comparison between seasonal fires. Maximum fire temperatures reached during burning averaged 853, 827 and 871˚C for Wrotham Park, Ten Mile Creek early and Ten Mile Creek late season fires, respectively. The temperatures that seeds were exposed to depended on their location within the vertical profile, with temperatures above fuel below fuel on rubber vine crown bare ground 0.5 cm below ground. Seed viability after burning ranged from 0 to 100%, with seeds generally most affected if located above or below the fuel, and least affected if buried below ground. The age of seed and the presence of seed plumes interacted with seed placement so that seed germination and viability of loose seeds were affected. Some seeds remained viable, but were inhibited from germinating, particularly if located 0.5 cm below ground. Positive, non-linear relationships occurred between seed mortality and maximum temperature and between seed mortality and the duration of exposure. These results suggest that fire may inhibit germination and kill a substantial proportion of rubber vine seeds.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/RJ17125
Abstract: Gamba grass (Andropogon gayanus Kunth.) is a highly invasive, naturalised Weed of National Significance in Australia due to its economic, environmental and social impacts. It outcompetes native pastures and fuels intense fires in northern Australian rangelands. To aid management of current infestations and to better understand its potential distribution, this study determined the germination response of gamba grass under a range of constant (13°C−48°C) and alternating (11/7°C–52/42°C) temperature regimes and quantified the potential longevity of soil seed banks. The effect of different soil types, levels of pasture cover and burial depths on seed longevity was investigated in the Dry Tropics of northern Queensland. Germination of gamba grass occurred under a wide range of both constant (17°C−39°C) and alternating day/night temperatures (16/12°C–47/39°C), although the level of germination declined at the lower and higher temperature ranges. At the cooler temperatures, seed viability was not affected, but seeds went into a state of dormancy. The highest level of seed viability was recorded at the lowest constant temperature regime (13°C) and at the two lowest alternating temperatures (11/7°C and 16/12°C). A gradual but variable decline in viability occurred thereafter with increasing temperatures. At the higher temperature range (e.g. constant temperatures of 39°C−43°C and alternating temperatures of 47/39°C) both dormancy and loss of seed viability were occurring, but once alternating and constant temperatures reached above 47/39°C and 43°C all seeds were rendered unviable after 9 and 6 weeks respectively. In the Dry Tropics of northern Queensland, viability of seeds was % after 12 months and nil after 24 months, irrespective of soil type or vegetation cover. However, burial depth had a significant effect, with surface located seeds exhibiting a faster rate of decline in germination and viability than seeds buried below ground (i.e. 2.5–10 cm). These findings have implications for the duration of control/eradication programs (i.e. seed persistence) and also suggest that gamba grass has the potential to greatly expand its current distribution into the relatively cooler southern latitude areas of Australia.
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/RJ12051
Abstract: Bellyache bush (Jatropha gossypifolia L.) is an invasive shrub that adversely impacts agricultural and natural systems of northern Australia. While several techniques are available to control bellyache bush, depletion of soil seed banks is central to its management. A 10-year study determined the persistence of intact and ant-discarded bellyache bush seeds buried in shade cloth packets at six depths (ranging from 0 to 40 cm) under both natural rainfall and rainfall-excluded conditions. A second study monitored changes in seedling emergence over time, to provide an indication of the natural rate of seed bank depletion at two sites (rocky and heavy clay) following the physical removal of all bellyache bush plants. Persistence of seed in the burial trial varied depending on seed type, rainfall conditions and burial depth. No viable seeds of bellyache bush remained after 72 months irrespective of seed type under natural rainfall conditions. When rainfall was excluded seeds persisted for much longer, with a small portion (0.4%) of ant-discarded seeds still viable after 120 months. Seed persistence was prolonged ( months to decline to % viability) at all burial depths under rainfall-excluded conditions. In contrast, under natural rainfall, surface located seeds took twice as long (70 months) to decline to 1% viability compared with buried seeds (35 months). No seedling emergence was observed after 58 months and 36 months at the rocky and heavy clay soil sites, respectively. These results suggest that the required duration of control programs on bellyache bush may vary due to the effect of biotic and abiotic factors on persistence of soil seed banks.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/RJ14130
Abstract: Understanding the reproductive biology of Calotropis procera (Aiton) W.T. Aiton, an invasive weed of northern Australia, is critical for development of effective management strategies. Two experiments are reported on. In Experiment 1 seed longevity of C. procera seeds, exposed to different soil type (clay and river loam), pasture cover (present and absent) and burial depth (0, 2.5, 10 and 20 cm) treatments were examined. In Experiment 2 time to reach reproductive maturity was studied. The latter experiment included its sister species, C. gigantea (L.) W.T. Aiton, for comparison and two separate seed lots were tested in 2009 and 2012 to determine if exposure to different environmental conditions would influence persistence. Both seed lots demonstrated a rapid decline in viability over the first 3 months and declined to zero between 15 and 24 months after burial. In Experiment 1, longevity appeared to be most influenced by rainfall patterns and associated soil moisture, burial depth and soil type, but not the level of pasture cover. Experiment 2 showed that both C. procera and C. gigantea plants could flower once they had reached an average height of 85 cm. However, they differed significantly in terms of basal diameter at first flowering with C. gigantea significantly smaller (31 mm) than C. procera (45 mm). On average, C. gigantea flowered earlier (125 days vs 190 days) and set seed earlier (359 days vs 412 days) than C. procera. These results suggest that, under similar conditions to those that prevailed in the present studies, land managers could potentially achieve effective control of patches of C. procera in 2 years if they are able to kill all original plants and treat seedling regrowth frequently enough to prevent it reaching reproductive maturity. This suggested control strategy is based on the proviso that replenishment of the seed bank is not occurring from external sources (e.g. wind and water dispersal).
Publisher: Cambridge University Press (CUP)
Date: 02-08-2021
DOI: 10.1017/WSC.2021.54
Abstract: Sweet acacia [ Vachellia farnesiana (L.) Willd.] is a problematic thorny weed species in several parts of Australia. Knowledge of its seed biology could help to formulate weed management decisions for this and similar species. Experiments were conducted to determine the effect of hot water (scarification), alternating temperatures, light, salt stress, and water stress on seed germination of two populations of V. farnesiana and to evaluate the response of its young seedlings (the most sensitive developmental stage) to commonly available postemergence herbicides in Australia. Both populations responded similarly to all the environmental factors and herbicides therefore, data were pooled over the populations. Seeds immersed in hot water at 90 C for 10 min provided the highest germination (88%), demonstrating physical dormancy in this species. Seeds germinated at a wide range of alternating day/night temperatures from 20/10 C (35%) to 35/25 C (90%), but no seeds germinated at 15/5 C. Germination was not affected by light, suggesting that seeds are nonphotoblastic and can germinate under a plant canopy or when buried in soil. Germination was not affected by sodium chloride (NaCl) concentrations up to 20 mM, and about 50% of seeds could germinate at 160 mM NaCl, suggesting high salt tolerance ability. Germination was only 13% at −0.2 MPa osmotic potential, and no seeds germinated at −0.4 MPa, suggesting that V. farnesiana seeds may remain ungerminated until moisture conditions have become conducive for germination. A number of postemergence herbicides, including 2,4-D + picloram, glufosinate, paraquat, and saflufenacil, provided % control of biomass of young seedlings compared with the non-treated control treatment. Knowledge gained from this study will help to predict the potential spread of V. farnesiana in other areas and help to integrate herbicide use with other management strategies.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/BT18117
Abstract: Stevia ovata Willd. is an invasive weed that has become naturalised in northern Queensland, Australia. To aid management of current infestations, this study evaluated seed germination under a range of constant (13−48°C) and alternating (11/7 to 52/42°C) temperature regimes and quantified the potential longevity of soil seed banks. The effect of different soil types, levels of pasture cover and burial depths on seed longevity was investigated in both the dry- and wet-tropics of North Queensland. Germination of S. ovata occurred under a wide range of both constant (13−39°C) and alternating day/night temperatures (16/12 to 52/42°C), but optimum conditions ranged between 24 and 27°C and 24/20 and 37/31°C respectively. As temperatures declined below the optimum, an increasing proportion of seeds went into a state of enforced dormancy. In contrast, higher than optimum temperatures caused a proportion of seeds to lose viability. Differential responses in seed longevity of S. ovata occurred between the two experimental sites. In the wet-tropics, seed viability was % after 12 months and fully expired after 18 months, irrespective of burial depth. In the dry-tropics, seeds persisted for longer (nil viability after 24–42 months) and burial depth had a significant effect. Surface located seeds tended to exhibit a faster rate of decline in viability than seeds buried below ground. These findings have implications for the duration of control/eradication programs and also suggest that S. ovata has the potential to greatly expand its current distribution, particularly into cooler areas of Australia.
Publisher: MDPI AG
Date: 12-2022
Abstract: Opuntia species (prickly pear) were deliberately introduced to many countries around the world for fruit, cochineal dye production, living fencing or as ornamentals. They are now some of the world’s most significant weeds, particularly in regions with warm and or dry climates, as they pose threats to economic and environmental assets. In addition, they can cause considerable health issues for humans and animals. Opuntia spp. have prolific reproduction abilities, being able to reproduce both vegetatively and by seed. They have generalist pollination and dispersal requirements, which promotes their establishment and spread. Opuntia stricta, O. monacantha and O. ficus-indica are the most globally widespread of the Opuntia spp. In many countries, biological control agents, particularly the cactus moth (Cactoblastis cactorum) and various cochineal insects from the Dactylopius genus, have successfully reduced land-scape scale populations. On a smaller scale, controlling these weeds by either injecting or spraying the cladodes with herbicides can provide effective control. Care must be taken during herbicide treatments as any untreated areas will regenerate. While biological control is the most cost and time effective control method for landscape-scale infestations, further research into the combined efficacy of herbicides, fire, grubbing and pre-burial techniques would be beneficial for land managers to control small-scale and establishing populations. It would also be useful to have greater knowledge of the potential seedbank longevity and seed ecology of these species so that integrated management strategies can be developed to not only deal with initial populations but also the subsequent seedling regrowth.
Publisher: MDPI AG
Date: 30-12-2021
Abstract: Whilst exotic invasive species are a major threat to natural and modified ecosystems around the world, management programs to reduce their impacts often fail due to a lack of information about their biology and how best to control them in various situations. This paper reviews the currently available information on the biology, distribution, and management options for the invasive weed Senecio madagascariensis Poir. (fireweed). In addition, we developed a model to predict the climatic suitability of this weed around the world based on the current climate. Senecio madagascariensis originates from southern Africa but it has been introduced to several other countries including Australia. Climatic suitability suggests that there are large areas around the world suitable for the weed’s growth where it is currently not present. The weed poses a major threat to livestock industries in these countries through its ability to reduce pasture production and poison animals. A range of control techniques have been used to try and manage S. madagascariensis. This paper highlights how a better understanding of the biology of S. madagascariensis can help determine the most effective treatments to impose and to further develop integrated management strategies. Besides using traditional approaches, the use of competitive pastures and more tolerant livestock (such as sheep and goats) are some of the other options recommended as part of an integrated approach. On-going research to identify host-specific biological control agents is also considered a priority.
Publisher: CSIRO Publishing
Date: 09-04-2021
DOI: 10.1071/CP20235
Abstract: Ground pearls (Hemiptera: Margarodidae), so called for their shiny spherical cyst stage, are important root-feeding pests of a broad range of plants predominantly belonging to the family Poaceae. In the tropical and subtropical regions of eastern Australia, ground pearl species cause significant damage on sugarcane and turf grasses and have been identified at multiple sites of pasture dieback in Queensland. The potential impact of ground pearls on pasture production in Australia and elsewhere is largely unknown. This paper reviews Australian and international literature on the biology and management of this poorly understood group of pests. Ground pearls have several features that make control difficult, including a resilient cyst which provides resistance to drought and excessive moisture, a relative impermeability to insecticides, and ease of dispersal through movement of soil. Ground pearls can also modulate the period of encystment to survive adverse environmental conditions, with some species capable of surviving for years while disassociated from a host. No insecticide effectively controls ground pearl cysts. Biological control agents have been identified for some species however, these pathogens are relatively ineffective on subterranean ground pearl cysts. Cultural control methods such as cultivation and fallowing have helped to reduce ground pearl populations in sugarcane. In turf, practices that maintain plant health such as adequate irrigation and nutrition can mask signs of ground pearl infestation. The paucity of research conducted on the biology and impact of ground pearls represents a constraint to improving management of this pest.
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/RJ14038
Abstract: Cascabela thevetia (L.) Lippold (Apocynaceae) is an invasive woody weed that has formed large infestations at several locations in northern Australia. Understanding the reproductive biology of C. thevetia is vital to its management. This paper reports results of a shade house experiment that determined the effects of light conditions (100% or 30% of natural light) and plant densities (one, two, four or eight plants per plot) on the growth, time to flowering and seed formation, and monthly pod production of two C. thevetia biotypes (peach and yellow). Shaded plants were significantly larger when they reached reproductive maturity than plants grown under natural light. However, plants grown under natural light flowered earlier (268 days compared with 369 days) and produced 488 more pods per pot (a 5-fold increase) over 3 years. The yellow biotype was slightly taller at reproductive maturity but significantly taller and with significantly greater aboveground biomass at the end of the study. Both biotypes flowered at a similar time under natural light and low plant densities but the yellow biotype was quicker to seed (478 versus 498 days), produced significantly more pods (364 versus 203 pods) and more shoot growth (577 g versus 550 g) than the peach biotype over 3 years. Higher densities of C. thevetia tended to significantly reduce the shoot and root growth by 981 g and 714 g per plant across all light conditions and biotypes over 3 years and increase the time taken to flower by 140 days and produce seeds by 184 days. For land managers trying to prevent establishment of C. thevetia or to control seedling regrowth once initial infestations have been treated, this study indicates that young plants have the potential to flower and produce seeds within 268 and 353 days, respectively. However, with plant growth and reproduction most likely to be slower under field conditions, annual surveillance and control activities should be sufficient to find and treat plants before they produce seeds and replenish soil seed banks. The most at-risk part of the landscape may be open areas that receive maximum sunlight, particularly within riparian habitats where plants would consistently have more favourable soil moisture conditions.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/RJ15104
Abstract: Chinee apple (Ziziphus mauritiana Lam.) is a thorny tree that is invading tropical woodlands of northern Australia. The present study reports three experiments related to the seed dynamics of chinee apple. Experiment 1 and 2 investigated persistence of seed lots under different soil types (clay and river loam), levels of pasture cover (present or absent) and burial depths (0, 2.5, 10 and 20 cm). Experiment 3 determined the germination response of chinee apple seeds to a range of alternating day/night temperatures (11/6°C up to 52/40°C). In the longevity experiments (Expts 1 and 2), burial depth, soil type and burial duration significantly affected viability. Burial depth had the greatest influence, with surface located seeds generally persisting for longer than those buried below ground. Even so, no viable seeds remained after 18 and 24 months in the first and second experiment, respectively. In Expt 3 seeds of chinee apple germinated under a wide range of alternating day/night temperatures ranging from 16/12°C to 47 /36°C. Optimal germination (77%) occurred at 33/27°C and no seeds germinated at either of the lowest (11/6°C) or highest (52/40°C) temperature regimes tested. These findings indicated that chinee apple has the potential to expand its current distribution to cooler areas of Australia. Control practices need to be undertaken for at least two years to exhaust the seed bank.
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/EA01129
Abstract: A 2-year study investigated fire as a potential control technique for the invasive woody weed Prosopis pallida (Willd.) K�nth by comparing changes in plant density and stem basal area between burnt and unburnt plots. Three months after burning only 8% of the original 1760 plants per hectare remained alive, compared with 100% survival in control plots. Over the ensuing 21 months, a further 2.5 and 21% of the original plants died in burnt and control plots, respectively, and 90% of control plants that died were young plants (less than 0.5 m in height). Burning also reduced recruitment of P. pallida during the 2 post-fire years, although very few seedlings that emerged remained alive at the end of the study period in either control or burnt plots. Two years after treatments were applied, the population of P. pallida in control and burnt plots had decreased by 7 and 93% of the initial populations, respectively. Similarly, the total stem basal area of P. pallida in burnt plots after 2 years was 0.9 m2/ha, 93% less than that in the unburnt controls. Seedling recruitment had a minimum impact on stem basal area in both control and burnt plots, contributing less than 0.005%. Subsequent control measures will be necessary to treat any plants not killed by fire and any new seedlings.
Publisher: MDPI AG
Date: 15-03-2023
Abstract: Fireweed (Senecio madagascariensis Poir.) is a herbaceous weed-producing pyrrolizidine alkaloid that is poisonous to livestock. To investigate the efficacy of chemical management on fireweed and its soil seed bank density, a field experiment was conducted in Beechmont, Queensland, in 2018 within a pasture community. A total of four herbicides (bromoxynil, fluroxypyr/aminopyralid, metsulfuron-methyl and triclopyr icloram/aminopyralid) were applied either singularly or repeated after 3 months to a mix-aged population of fireweed. The initial fireweed plant density at the field site was high (10 to 18 plants m−2). However, after the first herbicide application, the fireweed plant density declined significantly (to ca. 0 to 4 plants m−2), with further reductions following the second treatment. Prior to herbicide application, fireweed seeds in both the upper (0 to 2 cm) and lower (2 to 10 cm) soil seed bank layers averaged 8804 and 3593 seeds m−2, respectively. Post-herbicide application, the seed density was significantly reduced in both the upper (970 seeds m−2) and lower (689 seeds m−2) seed bank layers. Based on the prevailing environmental conditions and nil grazing strategy of the current study, a single application of either fluroxypyr/aminopyralid, metsulfuron-methyl or triclopyr icloram/aminopyralid would be sufficient to achieve effective control, whilst a second follow-up application is required with bromoxynil.
Publisher: MDPI AG
Date: 18-11-2021
Abstract: Mimosa bush (Vachellia farnesiana) is an invasive woody weed widely distributed in Australia. While it can be controlled using several mechanical and chemical techniques, this study evaluated a novel herbicide delivery mechanism that minimizes the risk of spray drift and potential non-target damage. This method, developed by Bioherbicides Australia, involves the implantation of encapsulated granular herbicides into the stem of intact plants or into the stump after cutting off plants close to ground level (cut stumps). Trials were implemented near Moree (New South Wales, Australia) on intact (two experimental runs) plants and cut stumped (two experimental runs) plants. For each trial, an untreated control plus the conventional basal bark application of a liquid formulation of triclopyr + picloram mixed with diesel was included for comparison. Encapsulated glyphosate, aminopyralid + metsulfuron-methyl, hexazinone and clopyralid were also tested in all trials. In addition, encapsulated triclopyr + picloram, and metsulfuron-methyl were included in one of the intact plant trials. Aminopyralid + metsulfuron-methyl was consistently most effective on cut stump and intact plants, whilst clopyralid provided highest mortality when applied to cut stumps and single-stemmed intact plants. Particularly for multi-stemmed intact plants, clopyralid should be applied to each stem. Overall, the highest efficacy was achieved on single stemmed plants, but with further refinement of the technique, it should be possible to achieve similar results for multi-stemmed in iduals. This method resulted in a reduction in the use of herbicide and environmental contamination while significantly improving speed of treatment.
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/EA01125
Abstract: If treatments imposed to control exotic plants also have a deleterious impact on their residual seed bank, the duration and extent of follow-up control may be reduced. Fire is one such technique that has this ability, particularly if seeds are located on or close to the soil surface. Three studies were undertaken in a riparian habitat in the dry tropics of northern Queensland to quantify the effects of spring burning on the seed bank of the exotic weed bellyache bush (Jatropha gossypiifolia). The first determined the distribution of seeds within the vertical profile of the trial site. The other 2 studies were experiments that quantified the effects of fire on germination and viability of both dispersed bellyache bush seeds and seeds held in mature capsules. Dispersed seeds of 2 types (intact and ant-discarded) were placed at the following 6 positions in the vertical profile of bellyache bush infestations: 0.5, 1, 2 and 4 cm depth below ground, on bare ground, and below fuel. Seeds held in capsules were located at random on the crown of bellyache bush plants. For both experiments, comparisons of burnt plots were made with unburnt controls. Fire was imposed in spring (September) the season in which burning for weed control in northern Queensland generally occurs. While maximum fire temperatures averaged 590 ± 46°C, the temperatures that seeds or capsules were exposed to depended on their location within the vertical profile, with temperatures decreasing in the following order: below fuel crown of bellyache bush 1 cm 0.5 cm bare ground 2 cm 4 cm below ground. There were negative correlations between seed germination and peak fire temperature and between viability and peak fire temperature. Seed viability was nil for seed under fuel but % for seeds placed on bare ground or ≥2 cm below ground. Fire reduced germination and viability of seeds held in capsules by 31 and 35%, respectively, when compared with unburnt seeds. While ant-discarded seeds generally had a higher germinability than intact seeds, they were more susceptible to fire. This may be attributed to loss of the external protective barrier of the seed coat (exotegmen) caused by the feeding of ants. Bellyache bush seeds were recorded across all soil depths, reaching a peak of 3.8 million seeds per hectare at 1–5 cm soil depth. These results suggest that while bellyache bush seeds are susceptible to fire, many are buried beyond the reach of lethal temperatures. Therefore, viable seeds will be available for post-fire recruitment and other measures, such as chemical control, may need to be employed in conjunction with burning.
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/RJ10038
Abstract: Bellyache bush (Jatropha gossypiifolia L.) is an invasive weed that has the potential to greatly reduce bio ersity and pasture productivity in northern Australia’s rangelands. This paper reports an approach to develop best practice options for controlling medium to dense infestations of bellyache bush using combinations of control methods. The efficacy of five single treatments including foliar spraying, slashing, stick raking, burning and do nothing (control) were compared against 15 combinations of these treatments over 4 successive years. Treatments were evaluated using several attributes, including plant mortality, changes in population demographics, seedling recruitment, pasture yield and cost of treatment. Foliar spraying once each year for 4 years proved the most cost-effective control strategy, with no bellyache bush plants recorded at the end of the study. Single applications of slashing, stick raking and to a lesser extent burning, when followed up with foliar spraying also led to significantly reduced densities of bellyache bush and changed the population from a growing one to a declining one. Total experimental cost estimates over 4 successive years for treatments where burning, stick raking, foliar spraying, and slashing were followed with foliar spraying were AU$408, AU$584, AU$802 and AU$789 ha–1, respectively. Maximum pasture yield of 5.4 t ha–1 occurred with repeated foliar spraying. This study recommends that treatment combinations using either foliar spraying alone or as a follow up with slashing, stick raking or burning are best practice options following consideration of the level of control, changes in pasture yield and cost effectiveness.
Start Date: 06-2023
End Date: 05-2027
Amount: $239,375.00
Funder: Australian Research Council
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