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An update on the biological control of Bellyache Bush
No full textJatropha gossypiifolia, commonly known as bellyache bush is a serious weed of rangelands and riparian zones in northern Australia. Bellyache bush has been the target of biological control since 1996 with the release of one agent, which failed to establish. Following field surveys in Peru, Bolivia and Paraguay, a leaf miner was prioritised for thorough host specificity testing. The bellyache bush leaf miner, Stomphastis thraustica was approved for release in Australia in September 2022. Field releases commenced in October 2022. By the end of 2024, 77 releases of the leaf
miner had been made at 31 sites across Queensland and three sites in the Northern Territory. During the host specificity testing of S. thraustica, an existing leaf miner on bellyache bush in Australia was also determined to be a Stomphastis species, though not S. thraustica. The Stomphastis species already present in Australia is widespread, found at nearly all sites where S. thraustica has been released in Queensland and the Northern Territory. It is also known to occur in Western Australia. Stomphastis species cannot be easily differentiated morphologically. To confirm the establishment of S. thraustica and whether interbreeding occurs between the two species in the field we are currently collecting larval samples from release sites for DNA analysis. We are also looking at the level of leaf miner attack (potentially from both Stomphastis species) across release sites in Queensland. The leaf miner is the first of several agents currently under investigation
Preventative surveillance for high-risk invasive species – Central Queensland case study
No full textPreventative surveillance is a pre-emptive and deliberate approach that facilitates the early detection of new incursions of priority invasive plants and animals. This ensures that subsequent responses are more cost-effective and maximises the likelihood of their success. Led by Biosecurity Queensland, this approach has been implemented in Central Queensland where the large land area (571,145 km2 or 31% of the state) combined with diverse climate, habitat, industries, land use and population demographics enable a myriad of new and emerging high-risk invasive species to be potential threats.
Coordinated preventative surveillance activities commenced in Central Queensland in 2020 with a selection of targets, development of surveillance plans, implementation of surveys, facilitation of capacity building and ongoing monitoring and review. This paper provides an overview of the program with specific reference to activities and outcomes for Siam weed, high-risk cacti, spiked pepper, high-risk invasive ants, Asian black spined toads and exotic turtles.
Extensive surveys have been completed, resulting in the detection and extirpation of multiple prohibited cacti sites, and proof of freedom confidence for other targeted highrisk invasive plants and animals. Through the program, there have also been learnings including target species identification and prioritisation, pathway and entry point determination, and adaptation of survey methodologies to the target and environment
Understanding the risk: real world application of the general biosecurity obligation, more than killing invasives
No full textThe Queensland Biosecurity Act 2014 (the Act) provides a ‘cohesive legislative framework for governments, industries and communities to respond to pest species in Queensland’. A significant change identified from previous legislation has been the transition from ‘prescriptive’ measures for control and management of invasive plants, to a risk-based approach. Management decisions made under the Act will depend on the likelihood and consequence of the pest impact not on the mere presence of the invasive species. The broadening of legislative responsibilities so that everyone now has a general biosecurity obligation (GBO) is a key mechanism within the Act that supports the risk-based approach of invasive plants, along with other legislative requirements for certain landholders.
The Act does not prescribe all the actions that are needed to meet the GBO in any given situation. It leaves much of what is required to those dealing with the biosecurity matter and associated risks and describes those actions required as what is reasonable and practical to minimise the risk associated with the biosecurity matter or activity in question. The determination of the risk associated with biosecurity matter and what are reasonable and practical measures to manage the risk will be influenced by many factors. It is therefore reasonable to assume that how biosecurity risks are managed may differ from land manager to land manager but be guided by Local Government Biosecurity Plans.
In this paper we discuss the complexities and application of the GBO in the real world context of managing risk associated with invasive plants with reference to giant rat’s tail grass and lantana, two significant invasive plants in Queensland
Comparison of equations to predict the metabolizable energy content as applied to lucerne
No full textMetabolisable energy (ME) intake determines productivity in ruminant production systems and estimates of the ME content of feeds underpin nutritional production models and feeding standards across the world. An inaccurate estimation of ME content of a feed means nutritional models and decision support tools are erroneous, resulting in significant variance in expected liveweight gain or carrying capacity of a pasture. Currently in Australia there are a range of equations used to estimate ME of feeds. Utilising appropriate ME equations suitable for Australian forages, in this case, lucerne, is vital for predictive modelling for production and for any required ration or supplement formulation. The current study compared 24 ME equations in lucerne. Lucerne samples were taken at four different vertical strata grown in field trials of plants of different heights to generate samples of differing nutrient quality.
This research demonstrated that different ME estimation equations generate different ME values for the same lucerne sample. This is exemplified with ME values ranging from 10.25 to 16.58 MJ ME/kg DM for a sample in the top strata, and 7.7 to 13.75 MJ ME/kg DM for another sample in the bottom strata. The Minson (1984) equation, ME (MJ/kg DM) = 0.157 DOMD + 0.059 CP – 1.073, appeared the best equation to use for lucerne according to its lowest SD. This was congruent to the ME equation analysis for forage sorghum samples (Lwin et al. 2022).
This study did not determine which equations were biologically correct, however ME equations based on a combined regression using DOMD and CP parameter were most suitable for use in both forage sorghum and lucerne. This work needs to be validated across multiple forages in Australia to develop ME feeding standards for wider and improved applications for the extensive grazing industry
The Effects of Myrtle Rust on Post‐Fire Regeneration of Myrtaceae in Australia
No full textFire is an important factor influencing the evolution, structure and composition of Australia's native vegetation. Australia's many fire‐adapted species regenerate en masse after fire, with a proliferation of new epicormic shoots and seedlings. Given Austropuccinia psidii (myrtle rust) mainly infects new growth, post‐fire emergence of new epicormic shoots and seedlings is ideal for the development of the disease, leading to further loss of plants along with subsequent increase of fungal inoculum in the region. Extreme fire events across New South Wales and Queensland in 2019–2020 and subsequent vegetation regeneration across a wide area provided ideal conditions for disease epidemics. Surveys for myrtle rust were conducted across rainforest, coastal heath and woodland environments from south‐eastern NSW to south‐east Queensland 6–12 months post‐fire. Myrtle rust was identified in all regions and ecosystems surveyed apart from areas in south‐eastern NSW. Of the 73 Myrtaceae species surveyed in areas other than southern NSW, 44 were found with myrtle rust symptoms, ranging from small spots and limited damage to severe blighting, dieback and death of reshooting trees and seedlings. Monitoring plots were established for some of the more susceptible species, with monthly assessments conducted to determine impact levels and decline rates. The most severely impacted species were Rhodamnia rubescens and Uromyrtus australis , with infections of reshoots causing dieback. Infection of Melaleuca quinquenervia and M. nodosa reshoots and seedlings impeded recovery of populations, causing seedling and tree deaths and reducing flower set and subsequent seed production
Enhancing Root Proliferation in an Alkaline Dispersive Subsoil: a Comparative Study of Organic and Inorganic Amendments with Different Amelioration Mechanisms
No full textPurpose: Alkaline dispersive subsoils contain a range of physicochemical constraints that restrict root proliferation and limit water and nutrient extraction, leading to yield penalties. We investigated the effectiveness of organic, inorganic and a combination of organic and inorganic (combined) amendments with contrasting chemical compositions in mitigating constraints on crops grown in these subsoils. Methods: An alkaline dispersive subsoil (20 – 40 cm depth) with pH w 8.9 and an exchangeable sodium percentage (ESP) of 12.9% was incubated for 14.5 months with 19 different organic (crop residues, animal manures and composted materials), inorganic (gypsum, polyacrylamide (PAM) and their combinations (PAM + Gypsum)) and combined (combination of wheat stubble and chemical fertilisers) amendments or control. The amendments were applied as a band within a soil core. Following incubation, the incubated subsoil was mounted on a custom-built sand core and wheat ( Triticum aestivum cv. Lancer) was grown. Water use was monitored weekly. Plant biomass, root biomass, root length density, and soil physicochemical properties were determined at harvest. Results: Organic amendments with a low C:N ratio (i.e., high N content) enhanced root proliferation (up to 63%) through the nutrient patches from the mineralising organic matter and improved porosity by macro-aggregate formation (84%), and promoting fungal (500%) and bacterial (47%) abundance. In contrast, inorganic amendments such as gypsum, alone or in combination with PAM, improved micro-aggregate formation (14%) by reducing soil pH (11%) and ESP (14%) and increasing electrical conductivity (EC; 97%). Wheat stubble, alone or combined with chemical fertilisers, significantly increased macro-aggregate formation (67%), root proliferation (61%) and water use (21%). Plant biomass and water use were associated with increased root proliferation through the amended soil layer. Conclusions: The co-application of organic and inorganic amendments with contrasting modes of action might have additive effects on ameliorating alkaline dispersive subsoils with multiple physicochemical constraints
Strengthening lightweight long-span timber floors: A study on vibration performance and human perception
No full textFloor vibration is a common serviceability issue in low-rise commercial buildings across Australia with lightweight long-span timber floors (LSTFs). In the absence of validated dynamic properties, calibrated numerical models, analytical reliable methods for predicting vibration responses and sufficient studies on human perception of vibration in LSTFs, developing an efficient design becomes challenging. This study aims to provide insights into these unknowns for a simply supported 8-meter LSTF comprised of steel-wood timber truss (SWTT) joists with a particleboard slab. The research experimentally measures static deflection, natural frequencies, and mode shapes of both the SWTT and the LSTF, and uses these results to validate the numerical models. Responses to footfall excitations of the LSTF, both with and without strengthening using strongbacks, are measured through comprehensive walking tests and surveys of participants. The experimental measurements and survey results are compared with predictions from existing international guidelines recommended for designing floors to resist footfall-induced vibrations. It is demonstrated that the inclusion of strongbacks is an effective method for mitigating excessive vibrations, both from the participants’ perspective and in terms of standard compliance. The correlations between participant survey results obtained through virtual reality (VR) technology and the comfort criteria recommended in international guidelines are highlighted in the discussion
Delivery of virus-specific dsRNA using a composite nanomaterial improves the protection of shrimp (Litopenaeus vannamei) against yellow head virus challenge
No full textAquaculture systems that produce crustaceans are often threatened by various diseases, particularly those caused by viruses. RNA interference (RNAi) is a promising technology that can enhance the resilience of aquaculture species against viral infections. The success of RNAi-based protection relies on the availability of efficient delivery systems for double-stranded RNA (dsRNA), the precursor molecule in this pathway. However, the instability of dsRNA is a major challenge for any control technology that aims to function in complex production systems, especially in aquatic environments. This study investigated composite polymer-clay nanoparticles, based on a bentonite biopolymer (BenPol), for their ability to protect dsRNA from degradation and improve its delivery to shrimp (Litopenaeus vannamei). A dsRNA targeting the protease gene of yellow head virus (dsYHV) was adsorbed within these nanoparticles to produce BenPol-dsYHV complexes. The results showed that the BenPol nanomaterial was capable of safeguarding the dsYHV from nuclease digestion and stabilizing it under simulated environmental conditions in a time-dependent manner. To evaluate the release efficiency of the BenPol-dsYHV complexes in shrimp, the complexes were prepared and stored at 4 °C for 3 or 8 days before injection into shrimp. The injected shrimp were maintained for 7 days prior to challenging with YHV. The findings revealed that shrimp treated with BenPol-dsYHV complexes prepared 8 days prior to injection had a 100 % survival rate compared to all other groups. Consequently, the 8-day prepared BenPol-dsYHV complexes were further tested to determine the duration of protection from YHV infection. Shrimp were injected with BenPol-dsYHV complexes for 7 and 21 days before YHV challenge. The results showed that the mortality rates in the BenPol-dsYHV complexes and dsYHV groups were 33 % and 69 %, respectively, for the treatments 7 days before YHV challenge. However, the mortality rate was similar when the interval between treatment and YHV challenge was 21 days. The possible mechanisms underlying these observations are discussed. The results of this study suggest that BenPol is a promising nanoparticle-based delivery platform for the safe and effective delivery of dsRNA to protect shrimp against viral infections in aquaculture production systems
Herbicide-Induced Fragmentation: Regenerative Ability of Cabomba Fragments After Exposure to Flumioxazin
No full textCabomba caroliniana A. Gray (cabomba) is an invasive alien aquatic plant (IAAP) posing a significant threat to aquatic ecosystems in Australia. Its ongoing spread is primarily driven by its rapid growth rate and ability to readily regenerate from stem fragments. Flumioxazin, an effective herbicide for controlling cabomba, has been registered for use in Australia since 2021. However, exposing cabomba to flumioxazin can induce stem fragmentation, potentially facilitating further spread. This study aims to determine whether stem fragments of cabomba following treatment at different flumioxazin doses (i.e., 25, 50, 100, or 200 ppb a.i.) can regenerate new healthy shoots that could contribute to its future spread in a new environment, in either summer or winter. This study also aims to investigate how this regrowth potential changes over time after herbicide application. Results show that flumioxazin suppressed the regeneration of replanted stem fragments in a dose-dependent manner in both winter and summer. In winter, complete regeneration was suppressed at the highest concentration tested (200 ppb a.i.), while low concentrations (25 and 50 ppb a.i.) resulted in an average 45% lower regeneration rate and 93% lower regenerated biomass than the control. In summer, suppression of regeneration was lower; at 200 ppb a.i., partial regeneration (18%) occurred with a 97% biomass reduction. At lower concentrations (25 and 50 ppb a.i.), more stem fragments regenerated (66%) and biomass reduction was lower (69%) compared to winter. Furthermore, in summer, the plants gradually regained their ability to regenerate over time after herbicide exposure, regardless of flumioxazin concentration, while no such recovery occurred in winter at any concentration. The findings show that the highest tested dose (200 ppb a.i.) can effectively suppress cabomba regenerative ability, which will greatly reduce the risk of new infestations caused by dispersed fragments, particularly in winter, when cooler temperatures and lower light are suboptimal for cabomba growth. This suggests that winter may be a more effective season for flumioxazin application. However, since some regeneration still occurred in summer, even at the highest tested dose, the highest registered label rate (400 ppb a.i.) may be necessary to ensure effective suppression under warmer conditions. Further studies are needed to evaluate this higher dose and its long-term efficacy
Characterizing wheat and barley growth and phenology using multi-spectral remote sensing for site-specific precision agriculture
No full textCrop phenology informs in-season management practices such as fertilizer and pest and disease controls to optimize final yield. However, tracking crop growth stages across spatiotemporal domains remains challenging, particularly in rainfed broadacre systems subject to climatic variability. This study uses sequential high-resolution Sentinel-2 imagery to estimate phenological stages of wheat and barley across the Australian grain cropping region which comprises >20 million ha of production. An analysis pipeline was developed to estimate main crop growth stages using targeted vegetation indices (VI) and statistical model fitting approaches. Model accuracy was validated against biophysical simulated phenology and field observations from diverse environments. Both parametric models and non-parametric models were evaluated to fill data gaps and capture growth dynamics. The double logistic model was selected for its balance of performance and efficiency. Strong alignment was observed between VI-derived features and simulated phenology. Peak and right shoulder features showed high accuracy for estimating stages of flag leaf (R2 = 0.61, root mean square error (RMSE) = 8.67 days) and flowering (R2 = 0.7, RMSE = 7.66 days). Scalability was evaluated at 110 and 73 fields across Australia, for 2021 and 2022 seasons, respectively, showing moderate to high correlations with recorded phenology (flag leaf R2 = 0.57–0.58; flowering R2 = 0.7–0.85). The method also predicted tillering (R2 = 0.2–0.7), maturity (R2 = 0.73–0.85), and harvest (R2 = 0.55–0.66) where these observations were available. These results demonstrate the utility of high-resolution satellite data for estimating crop phenology and supporting zonal in-season agronomic management