Invasive plant ecology and management research

Weed seed dynamics

Research officers: Simon Brooks and Dannielle Brazier

This project aims to provide 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, parthenium and gamba grass. Testing for prickly acacia 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 is also running controlled ageing tests to compare seed longevity under field burial conditions with a shorter ageing test under specific laboratory conditions. This project also conducts experiments to identify seed germination requirements to understand a weeds range and emergence triggers.

Ecology and 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 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 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.

Encapsulated herbicide control of woody weeds

Research officers: Simon Brooks, Danielle Brazier and Clare Warren

Stem injection has been identified as a possible, but under-utilised tool for the control of woody shrubs and small trees. There is now a new tool to deliver dry granular encapsulated herbicides directly into woody stems. This method is particularly safe to applicators as there is no need to mix with water or diesel as a carrier, or to have any contact with the herbicide. This method is also safer for the environment as the herbicide is contained in the target plant. As such, it may be suitable for use near creeks and rivers and in Great Barrier Reef catchments where herbicide runoff is a concern.

This project will initially test five active ingredients on weeds such as Chinee apple and parkinsonia. In subsequent years the project will use field trials to refine the rates of the most effective herbicides relative to stem size. The project will also investigate the efficacy of encapsulated herbicides on weeds such as pond apple, weedy Leucaena and neem. Where gaps in past control research are identified; weeds such as prickly acacia, blue thunbergia (tubers) and yellow bells may also be tested.

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 glush weed (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.

Sicklepod ecology and control

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.

Efficacy of foliar herbicides on Aleman grass

Research officers: Melissa Setter and Stephen Setter

This project consists of a field-based herbicide trial which will be conducted in the lower Herbert and Murray River basins with in-kind support from Hinchinbrook Shire Council, Cassowary Coast Regional Council, Mungalla Aboriginal Corporation, Canegrowers Tully and FNQROC. The first component of the trial will investigate effective herbicide/wetter rates for the control of Aleman grass in field situations. If the findings are successful, they will be used to make recommendations for a minor use registration for Aleman grass control to the Australian Pesticides and Veterinary Medicines Authority. If the herbicide trial is not conclusive or successful, an additional screening process will be lodged separate to this application. In addition, the trial will test the field efficacy and application of ‘Nemo’ wetting agent as a candidate to replace ‘Bonus’ which is currently the only aquatic wetter registered for use and has been withdrawn from the Australian market.

Tolerance of gamba grass and native plants to pre-emergent herbicides

Research officers: Melissa Setter, Stephen Setter and Clare Warren

This trial will provide herbicide information to improve management of gamba grass and restoration of native plant communities following gamba grass control. Pre-emergent herbicides will be tested on co-occurring native plant species and gamba grass to determine herbicide efficacy and species tolerance of each herbicide. The test species and herbicides have been determined by consultation with relevant colleagues and experts and from the outcomes of a gamba grass workshop held in Cairns in 2019.

Management of giant rat’s tail grass

Research officers: Wayne Vogler and Clare Warren

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. This project aims to fill some of these knowledge gaps around use of flupropanate, effective use of fertiliser, the effect of fire on flupropanate and giant rats tail grass (GRT) management in seasonally wet areas to improve the management of GRT in a range of 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.

Integrated control of parthenium in southern Queensland

Research officers: Olusegun Osunkoya and Christine Perrett

Landholders are managing Parthenium hysterophorus (parthenium weed) 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 weed, 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 weed’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 and frequency of herbicide control and the effect of grazing pressure on the weed growth. We have established experimental field plots which also serve as demonstration plots for landholders. Aerial imagery has been captured at two field sites (Gayndah and Monto) to provide a pre-trial baseline as well as to compare remotely-sensed demographic data of the weed with that obtained via small-scale ground-truthing. This will require identification of a parthenium spectral signature, necessary for surveys elsewhere for monitoring to direct control and evaluating control programs.

Prioritising pest management at multiple scales

Research officer: Olusegun Osunkoya

This is an Australian Research Council Linkage project with University of Queensland, Queensland University of Technology and Queensland Parks and Wildlife Service (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, invasive species management groups, like Biosecurity Queensland 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. A lack of coordination across agencies can 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.

Spatial and temporal dynamics of Queensland pests

Research officers: Olusegun Osunkoya and Christine Perrett

Weeds and pest animals have been prioritised for research and management based on their distribution, current and future impact using data extracted from the Annual Pest Distribution Survey (APDS). This information was coupled with stakeholder consultation at the regional level, However, such a prioritization exercise did not consider the speed and patterns of invasions - a set of traits that are obtainable from standardized invasion curves. We have now combined the short-time APDS estimates (2003-2014) with long-term herbarium records (HERBRECS) (>150 years) for many established and emerging weeds of Queensland, and used the datasets 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 for cost-efficient management.

Impact and management of Navua sedge

Research officers: Olusegun Osunkoya and Christine Perrett

There are few quantitative, scientific data on the yield loss to the grazing and cropping industries caused by Navua sedge. Our initial aim is to establish field plots in far north Qld to estimate current and potential yield loss caused by the weed under varying grazing and herbicide treatments with palatable pasture grass species (e.g. Humidicola and Signal grasses). We will (i) establish field experimental and demonstration plots, survey the plots to identify high-medium-low infestation subplots, and (ii) thereafter impose appropriate grazing and herbicide treatments. Once the plots have been established and treatments imposed, we will again survey the experimental plots and quantify the yield loss, and changes in soil seed bank composition and abundance caused by different levels of infestation of Navua sedge. This will be a one-year feasibility project, with the possibility of a three-year project extension.

Integrated control of aquatic weeds

Research officers: Tobias Bickel, Christine Perrett and Bahar Faharani

Flumioxazin effectively controls a range of established and emerging aquatic weeds. It provides excellent control of cabomba at low application rates is a promising tool to manage sagittaria, salvinia and other floating weeds. These are Weeds of National Significance and currently difficult to manage due to a lack of control options. This work will continue research carried out over the last two years in collaboration with CSIRO. While CSIRO will focus on cabomba biocontrol, our research will investigate herbicidal control techniques and strategies.

Supporting pest control with pesticide permits

Research officers: Joe Vitelli and David Holdom

The project will facilitate the development of chemical registration submissions and review and evaluate permits and products for herbicides used by Biosecurity Queensland 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 45 minor or emergency use permits issued to Biosecurity Queensland by APVMA and a further seven permits issued to other states (on which Biosecurity Queensland requested Queensland be included) that allows for the control of declared and emerging weeds found in Queensland.

Control of giant rat’s tail grass using native and naturalised pathogens

Research officers: Joe Vitelli, Annerose Chamberlain, Tim Boniface and Drew Rapley

Sporobolus is a genus of ~200 grass species in tropical and subtropical parts of the world, including Africa, temperate and tropical Asia, Australasia, North and South America. In Australia, 19 species are endemic, and a further eight 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.

Exploring environments within Australia where both native and naturalised species within the Sporobolus indicus complex coexist has provided us with a nursery of pathogens capable of controlling GRT. Research will prioritise the endemic isolated pathogens and determine pathogenicity on 15 native Sporobolus species and ten closely related and or introduced pasture species. Given there are native species in the same genus, studies will be required to select the most promising pathogen to lower the risk to biodiversity and increase productivity in Queensland and New South Wales.

Control of giant rat’s tail grass using wick wipers

Research officers: Joe Vitelli, Annerose Chamberlain, Tim Boniface and Drew Rapley

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 is reducing the carrying capacity and productivity of >450,000 ha of pastoral land in eastern Queensland, New South Wales and areas of Victoria and is also a high-risk fodder contaminant. Despite a weedy Sporobolus grasses best practice manual and the widespread use of these control strategies, effective control has not been achieved and weedy Sporobolus grasses continue to rapidly spread into new areas. However, producer and local government uptake of integrated management methods for GRT in open pasture paddocks is building. There is an increase in wick-wiper use, requiring timing of grazing pressure, but a limited understanding on how to use herbicides more effectively in the presence of endemic and naturalised pathogens to achieve GRT management. 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.

Flupropanate control of giant rat’s tail grass

Research officers: Joe Vitelli, Tim Boniface and Drew Rapley

Despite the use of flupropanate in Australia since the early 1970s, there is a lack of reliable data regarding its fate, degradation and behaviour in the environment. Insight into the residual level of flupropanate post application will greatly assist in the timing of follow-up treatments and potentially improve management options.

Through a collaborative project with Powerlink, two trials have commenced. The first investigates the use of flupropanate on a range of soils in the hope that knowledge gained will improve the effectiveness of flupropanate when managing tussock grasses and the second trial will determine flupropanate concentration required to effectively control or suppress tussock seedling emergence and what concentrations of flupropanate begin to have adverse effects on competitive pasture emergents.

During 2017-18 a potted trial involving five soil types (chromosol, dermosol, ferrosol, kurosol and vertisol) and two application method (liquid and granular) were established to determine the residual behaviour of flupropanate. An in vitro dose response trial was also undertaken to determine the susceptibility of three Sporobolus spp. and five competitive pasture species to 10 different flupropanate concentrations.

The trial will go for 60 months with pots being watered three times a week. In April of each year a subset of the pots are removed, plants dried and grounded and soil sieved in readiness for analytical determination of flupropanate levels.

Red witchweed eradication

Research officers: Joe Vitelli, Natasha Riding and Anna Williams

Red witchweed is considered to be amongst the world’s worst weeds. Once established, eradication is extremely difficult and control programs are expensive and prolonged (e.g. $260 million over >50 years in the USA). Current efforts in Queensland indicate that we are on track to eradicating red witchweed from Australia in 8-10 years.

An integrated control study was initiated in 2014 in the sugarcane-growing area of Habana in central Queensland, to investigate the efficacy of agronomic practices for depleting the red witchweed seed bank and preventing further seed production over a 10-year period. Pre- and post-emergent herbicides are being applied to sugarcane and being compared with catch crops, trap crops and fumigants. A new potted trial will be established at the Ecosciences Precinct to determine whether seed depletion of red witchweed can be accelerated with a continuous false host soybean crop, punctuated with multiple applications of the fumigant ethylene.

Fireweed management

Research officer: Joe Vitelli

A field research program is investigating the fundamental seed biology and ecology of fireweed followed by integrated weed management (IWM) studies. Early research was directed onto what currently appears to be the five most important contributing factors to fireweed persistence, viz. 1) seed primary and secondary dormancy, 2) seed viability contributing to longevity, 3) seed production and soil seed bank size, 4) seed dispersal, and 5) allelopathy. This was followed with management strategies involving chemical and physical control under grazing. The work has been undertaken in glasshouses (seed bank dynamics), in growth rooms (environmental influences on seed production), in the laboratory (biochemical studies on dormancy and germination, longevity and seed reduction and kill) and in the field (IWM strategies).