Weed ecology and management research

Weed seed dynamics

Research officers: Simon Brooks, Dannielle Brazier and Clare Warren

This project aims to provide a comprehensive information on the seed ecology of ‘Restricted matter’ and priority weeds across north Queensland. This information will assist land managers when developing control programs by providing an indication of how long they may need to treat sites once a control program is started, providing there is no further seed input. The seed burial trial site allows the longevity of seeds to be determined at different depths of burial in black clay and river loam soil types and under bare ground or full grass cover conditions. Testing has been completed on Chinee apple, calotrope, captain cook tree, neem tree, mesquite, yellow bells, lantana, leucaena and gamba grass. Testing for prickly acacia, parthenium, and sicklepod is still running and more grass species may be added. To provide further evidence of their seed longevity, seedling emergence studies have been implemented on Chinee apple, leucaena, prickly acacia, mesquite and neem tree. This project has also been running controlled ageing tests to compare seed longevity under field burial conditions with a shorter aging test under specific laboratory conditions. This project also conducts experiments to identify seed germination requirements to understand weeds range and emergence triggers.

Research supporting the management of nationally significant tropical weeds

Research officers: Simon Brooks and Kirsty Gough

This project provides support to the National Four Tropical Weeds Eradication Program (NFTWEP) by undertaking ecological and control research. Research focusses on seed longevity studies, determining age to reproductive maturity and identifying effective herbicides. This project will continue gathering Melastome growth and other data to investigate detection probabilities. This project also develops and reports on indicators of progress towards eradication based on field data from control teams.

Siam weed and clidemia were previously the target of national eradication programs but they have transitioned to on-going management programs after it was not considered feasible to eradicate them. Most recent clidemia and Siam weed research has concluded and the findings are being written up, and this project continues to provide technical advice to staff and stakeholders implementing the plans.

Ecology and management of Wet Tropics weeds

Research officers: Melissa Setter and Stephen Setter

Weeds are a major threat to the economic productivity and environmental integrity of the Wet Tropics. Many economically significant industries (including agriculture, horticulture, fisheries and forestry) are affected if Wet Tropics weeds are not managed effectively. Weed encroachment can decrease biodiversity, placing rare and threatened communities and species at risk. Socially, weed invasion can decrease people’s enjoyment of the Wet Tropics (e.g. by affecting recreational fishing through debilitation of fish nurseries, by reducing scenic quality of natural areas, by decreasing the diversity of birds). Both the social and environmental considerations also affect the high tourism value of the region.

There is a paucity of information on several key weed species threatening the Wet Tropics Bioregion. Study species include two Weeds of National Significance, and several others declared under state and/or local government legislation. Research is targeted at key aspects that will support on ground management, such as determining the longevity of seed banks, age to reproductive maturity, dispersal mechanisms, and control options. Research includes herbicide trials, rate of spread, and seed longevity in soil and water. Species studied have included pond apple, hymenachne, navua sedge, neem tree, leuceana, and bellyache bush.

Ecology and management of Stevia ovata

Research officers: Melissa Setter and Stephen Setter

Stevia ovata (Candy leaf) is an emerging weed whose only Australian records are in the southern Atherton Tablelands of north Queensland. It is deemed such a threat to the area that it is declared under local law by the Tablelands Regional Council (TRC), ranking as the sixth highest priority weed in their Pest Management Plan 2013-17. It is also included in weed lists from the FNQPAF (Far North Queensland Pest Advisory Forum) and WTMA (Wet Tropics Management Authority) and listed as category 3 restricted biosecurity matter in the Biosecurity Bill.

A Stevia ovata Working Group comprising stakeholders such as local government, state government, energy companies and landholders requested research into herbicide control of Stevia ovata, along with some basic biology studies to quantify seed bank longevity and age to reproductive maturity.

Research into the following aspects has been completed:

  • Germination requirements
  • Reproductive maturity
  • Seed longevity in soil (in Wet and Dry Tropics)
  • Seed longevity in water
  • Pilot herbicide screening
  • Herbicide screening
  • Rate refinement trial
  • Low volume/high concentration “splatter”
  • Pre-emergent herbicides

Ecology and control of aquatic weeds of north Queensland

Research officers: Melissa Setter and Stephen Setter

Aquatic weeds are a burgeoning problem with the increase in commercial trade of aquatic plants, particularly via the internet. Several escaped aquarium plants are particularly problematic in the Wet Tropics, but with potential distributions across large parts of northern Australia. These include Hygrophila costata, Bogmoss (Myacca fluviatilis), and Amazonian Frogbit (Limnobium laevigatum). This project proposes to answer specific ecological questions to improve management of current infestations and predict/restrict further infestations. Control options will also be investigated for selected species.

Specifically, research is currently planned into:

  • Seed and vegetative reproduction abilities in regional populations of Glush Weed.
  • Herbicide control of Bogmoss.
  • Seed viability and longevity in regional populations of Amazonian Frogbit.

Other species and activities may be incorporated if the need arises.

Ecology and management of sicklepod

Research officers: Melissa Setter and Stephen Setter

Sicklepod (Senna obtusifolia) is a serious weed of many parts of northern Queensland, from Cape York to Mackay, and in many situations, including pastures, crops, and corridors such as road and powerline clearings and creek banks.

In this project, we aim to improve management tools for sicklepod by investigating:

Seed longevity and production

Some ecological information currently being used lacks substantiation, particularly regarding the longevity of the seed bank in local conditions, which can have enormous impact on management decisions. Reproductive characteristics such as timing of and age to seeding will also be investigated.

Pre-emergent herbicide efficacy

A number of post-emergent herbicide control options are available for sicklepod, however regional stakeholders have specifically requested that pre-emergent herbicide options be investigated. This is because sicklepod has a relatively short life cycle that occurs during the wet season when access to plants can be limited. To optimise effect of pre-emergent residual herbicides, investigation of seasonality of seed production and environmental triggers for germination (rainfall and temperature) relative to local conditions may also require some investigation.

Low-volume/high-concentration herbicide application techniques

These techniques are particularly suitable for areas with poor vehicle accessibility, and several selected herbicides and possibly different application equipment will be tested for their efficacy on sicklepod.

Management of giant rat’s tail grass

Research officers: Wayne Vogler and Clare Warren

There has been a significant amount of work done on GRT since the mid 1990s on the ecology, management and potential biological control of this weed. The findings of this research have been published in two editions of a management manual the last of which was completed in 2007. However knowledge gaps around use of flupropanate, effective use of fertiliser, the effect of fire on flupropanate and GRT management in seasonally wet areas remain. This project aims to fill in some of these knowledge gaps to improve the management of giant rats tail grass (GRT) in a range of situations including grazing, peri-urban and forestry.

The project will be conducted in conjunction with Gladstone Regional Council and Economic Development Queensland to address issues raised by these organisations but that have broad application across most management situations. Small scale plot and/or pot trials will be conducted over a number of years to provide answers to specific knowledge gaps, the outcomes of which will assist current GRT management programs.

Improved herbicide options for weeds in north Queensland

Research officers: Wayne Vogler, Melissa Setter, Stephen Setter, Dannielle Brazier and Clare Warren

This project aims to improve herbicide control options for priority weeds in cental and northern Queensland.

A current focus is increasing the range of species that can be controlled using low volume, high concentration herbicide applications (e.g. splatter guns). The use of low volume, high concentration applications of herbicide has proven effective for control of lantana, bellyache bush and Siam weed growing in difficult to access areas as treatments can be applied using backpack style equipment. Land managers and local government officers are now seeking low volume, high concentration options for other priority weeds, such as prickly acacia (seedling regrowth) (Vachellia nilotica), rubber vine (Crypostegia grandiflora ), Chinee apple (Ziziphus mauritiana) and Gamba grass (Andropogon gayanus).

A project to look at Splatter gun technology for the control of high priority rangeland weeds in northern Australia was funded by Department of Agriculture and Water Resources until March 2020. This was sub contracted to the University of Queensland (Shane Campbell) to complete with support from researchers at TWRC.

Grader grass (Themeda quadrivalvis) flourishes throughout Cape York Peninsula, including many areas with limited accessibility in the wet season. A herbicide that can be applied towards the end of the dry season and activated with the first substantial rains of the Wet Season would be a significant aid to land managers.

Integrated control of parthenium in southern Queensland

Research officers: Olusegun Osunkoya, Kunjithapatham Dhileepan, Jason Callander and Christine Perrett

Landholders are managing Parthenium hysterophorus in central and northern Queensland through a combination of herbicide control and varying grazing pressure, and are supported by eleven biocontrol agents. In southern Queensland, at the invasion front for parthenium, landholders are having less success in managing the weed. There are a number of potential reasons for this, including biological control agents are few or not long established, the climate and vegetation differ and parthenium’s life history appears different (e.g. timing and extent of flowering) to that in the north. Landholders are also not familiar with managing the weed, particularly the integration of biological and conventional control techniques. In July 2018, we commenced collaborative work with North Burnett Regional Council in the field to experimentally examine a range of control strategies for parthenium. The project aims to determine the efficacy of biocontrol agents, optimal timing of herbicide control and the effect of grazing pressure on the weed growth. Experimental field plots are being used as demonstration plots and to provide extension to landholders. Aerial imagery was captured at one field site (Gayndah) to provide a pre-trial baseline as well as to compare remote sensed demographic data of the weed with that obtained via small-scale ground-truthing. Prospects to develop parthenium spectral signature, necessary for optimization of automated future landscape/landuse surveys, was discussed with BQ, QUT and Aspect imaging with promising collaboration opportunity.

Using pest distribution to assess pest risk and prioritise management

Research officers: Olusegun Osunkoya, Bradley Gray, Moya Calvert and Christine Perrett

This two-year extension builds on previous work on pest species prioritization and analyses of data from the Annual Pest Distribution Survey (APDS), a dataset spanning 2003-2014. Using the APDS data and stakeholder consultation at the regional level over 2016 – 2019, weeds and pest animals have been prioritized for research and management based on their distribution, current and future impact. However, such prioritization did not take into consideration the speed and patterns of invasions - a set of traits that are obtainable from standardized invasion curves. At the management level, invasion curves to guide control options are readily mentioned, but none has been constructed for any pest species in Queensland. We aim to combine the short-time APDS estimates (2003-2014) with long term herbarium records (HERBRECS)(> 150 yrs.) to develop standardized invasion curves. The standardized invasion curves can monitor, confirm or predict the temporal and spatial dynamics of both recent introductions (emerging species) and the widespread/established pests at regional and statewide scales. The information is critical to cost-efficient management effort and the implementation of appropriate rapid-response technique/s.

Collaborative prioritisation for improved invasive species management at multiple scales

Research officers: Olusegun Osunkoya, Bradley Gray, Moya Calvert and Christine Perrett

This is an ARC Linkage project with UQ, QUT and QPWS. Managing invasive species is complex. By necessity, it involves a range of different societal actors, including government departments and agencies, and non-government sectors (e.g. indigenous management groups and individual landowners). Further complexity arises because invasive species affect a diversity of land tenures that span multiple jurisdictions. A single invasive species (e.g. foxes) can occur on both agricultural lands and protected areas, cross multiple local and regional governmental boundaries, and span freehold, leasehold and public land. Presently, the invasive species management groups, like BQ and QPWS, almost always operate independently due to different jurisdictions and varying goals. However there are potential benefits of a collaborative approach across agencies to planning and action in this space. A lack of coordination lead to the inefficient use of limited resources and, importantly, reduced benefits for the environment and society. The aim of this Linkage Project is to develop and apply a new pest animal and plant prioritisation framework that recognises the fact that invasive species are managed at multiple spatial scales, and by multiple agencies.

Integrated control of aquatic weeds

Research officers: Tobias Bickel and Christine Perrett

Previous research showed that Flumioxazin controls a wide range of established and emerging aquatic weeds, such as sagittaria, salvinia and amazon frogbit. In particular, it achieves excellent control of cabomba at very low concentrations and will be the only tool available to control new detections of other submerged aquatic weeds. Cabomba and sagittaria are WONS species and currently difficult to control as efficient herbicides or biocontrol options are not available.

We will continue our five year project on integrated management of cabomba and other aquatic weeds in collaboration with CSIRO. While CSIRO research focuses on cabomba biocontrol, our research will investigate aquatic herbicide control techniques and strategies. In this year we will focus on application techniques in larger lakes to determine application rates and techniques to maximise the efficacy of flumioxazin to control cabomba in larger systems. For example, we will develop and test new application techniques to maximise efficacy to control submersed aquatic weeds while minimizing cost and non-target damage. We will also investigate the uptake, breakdown and environmental fate of flumioxazin in a natural environment.

In this year we aim to (1) start field trials in a reservoir (2) determine the fate of flumioxazin once applied to natural water bodies and (3) collaborate with CSIRO and SEQwater for future integration of biological and herbicidal control options in drinking water reservoirs.

It has to be stressed that while the current project focuses on cabomba, we use this species as a model organism and the output of this project will deliver invaluable information for best management practice to control a wide range of aquatic weeds more efficiently in the future.

Control packages for weed eradication targets

Research officers: Joe Vitelli, Natasha Riding, Anna Williams and Annerose Chamberlain

Project aims to develop reliable and effective control options that can be integrated into eradication programs for Queensland Prohibited and Restricted pest plants. The project will have a state-wide focus, bridging both aquatic and terrestrial environments, and will combine field, glasshouse and laboratory studies. Red Witchweed (RWW), Fireweed and GRT will be the main species targeted in 2019/20.

GRT: Little is known about the relative outputs (volumes) of the various wipers on the market, nor about factors affecting the deposition of herbicide from these wipers. This variability by each device and between devices makes it difficult to give precise recommendations on the herbicide concentrations needed to kill weeds. Researchers and chemical companies are often providing conservative recommendations on spray volumes (2-50L ha -1) and herbicide concentrations required that would give good control when using wiper applicators. Glyphosate is considered to be the best herbicide for the wiper application as it is highly systemic but its broad spectrum control often reduces its usage in pasture situations. More selective herbicides such as flupropanate though effective at controlling tussock grasses such as GRT, fail to reduce seed viability with paddocks treated with flupropanate for the control of GRT continue to produce seeds with high viability (>85%) 12 months after application. This project aims to optimise two herbicides (glyphosate and flupropanate) and the spray volume required to control and suppress seed production of GRT plants growing in pastures and along roadsides through the use of weed wipers.

Improving pest control activities through timely submission of permits

Research officers: Joe Vitelli and David Holdom

The project will facilitate the development of chemical registration submissions and the review and evaluation of permits and products for herbicides used by DAF and local government authorities for the control of invasive plants. Timely permit submissions will ensure 1) key deliverables within the Invasive Plants and Animals Program are met, 2) extended delays in acquiring new emergency and minor use permits to control declared pest plants and animals are minimised, and 3) an effective network is maintained with the Australian Pesticides and Veterinary Medicines Authority (APVMA), leading to a seamless renewal and extension of permits.

There are currently 44 minor or emergency use permits issued to Biosecurity Queensland by APVMA and a further 6 permits issued to other states that Biosecurity Queensland sought inclusion for Queensland to be added. These permits allow for the control of declared and emerging weeds found in Queensland.

Impact of native pathogens on giant rat’s tail grass

Research officers: Joe Vitelli, David Holdom, Jane Oakey, Wayne Vogler and Roger Shivas

Field surveys of endemic pathogens of Sporobolus in Australia was undertaken with funding through the Australian Government Rural R&D for Profit Grant, with money leveraged through industry, state and local government contributions. Sporobolus is a genus of about 200 grass species in tropical and subtropical parts of the world, including Africa, temperate and tropical Asia, Australasia, North and South America. In Australia, 18 species are endemic, and a further six species are naturalised weeds. Giant rat’s tail grass (GRT) and the other introduced weedy Sporobolus grasses are unpalatable, perennial, tussock-forming grasses of serious concern to the grazing industry across eastern Australia. GRT reduces carrying capacity and productivity of more than 450,000 ha of pastoral land in eastern Queensland, New South Wales and areas of Victoria and is a high risk fodder contaminant.

This project will target two outcomes: 1) Utilising molecular tools to better target weedy Sporobolus classical biological control agents and effectively study the genetic diversity of Sporobolus; and 2) to investigate endemic Australian pathogens.

This pathogen survey project has identified over 500 fungal isolates belonging to 13 different genera. Eight genera ( Stagonospora, Microdochium, Colletotrichum, Neopestalotiopsis, Pestalotiopsis, Phoma, Septoria and Curvularia) are known to be pathogenic grass fungi worldwide. Three species have been recognised as new, and more isolates remain to be characterised. In addition, the pathogen survey uncovered the first record of the leaf smut Ustilago sporoboli-indici in Australia (GRT leaf smut) in 2017, which was previously only known from South Africa on GRT. The smut fungus produced black sori spores in the leaves, leaf sheaths and stems which rendered infected shoots almost sterile with very limited seed head production. GRT leaf smut has since been found in the Queensland regional areas of Bundaberg, Conondale, Childers, Gin Gin, Miriam Vale and Taunton, spanning a distance of greater than 350km. This smut can infect a large number of GRT shoots indicating that it has the potential as a classical biocontrol agent in Australia. The utilisation of endemic pathogens for the control of GRT in Australia at this stage remains untested.