Invasive plant ecology and management research

Integrated control of aquatic weeds

Project Leader: Tobias Bickel

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

New aquatic weed management tools

Project Leader: Tobias Bickel

Aquatic weeds are a serious threat to agricultural, amenity and environmental aspects of Queensland’s valuable freshwater resources. Despite the profound impacts of aquatic weeds, there are few effective control options. Foremost, there is a lack of efficient herbicides that control the wide range of aquatic weeds affecting lakes, reservoirs, wetlands and irrigation systems. Consequently, aquatic weed management is often conducted haphazardly and results in poor control. This project will research two new aquatic herbicides (flumioxazin and florpyrauxifen-benzyl) and their efficient and safe use in various situations. We will determine the required herbicide dosage to effectively control different aquatic weeds under various environmental conditions and monitor herbicide breakdown and fate in sensitive aquatic environments. This research will develop innovative herbicidal control tools for many exotic aquatic weeds that are currently difficult or impossible to control.

Management of aquatic weeds in sensitive environments

Project Leader: Tobias Bickel

Herbicides are a useful tool to control aquatic weeds in a range of water bodies. However, application of herbicides to water bodies can result in significant damage to non-target aquatic plants. Native aquatic plants perform important ecosystem functions and need to be protected. This project aims to develop new herbicidal control options to manage aquatic weeds such as salvinia in sensitive aquatic ecosystems while limiting impacts on desirable native vegetation.

Advancing the detection, control and management of Siam weed in northern Australia

Project Leader: Simon Brooks

The ability of land managers to effectively control Siam weed across Queensland and the Northern Territory is limited by a lack of consolidated and local best practice information. This project will investigate the effectiveness of different control techniques and provide best practice information to better address the goals of individual land managers. The project is also investigating several possible technologies to remotely detect Siam weed from the air. Aerial imagery has been collected in Queensland and will be used to train detection models for use across northern Australia.

Research supporting the management of nationally significant tropical weeds

Project Leader: Simon Brooks

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. Project staff and collaborators continue to gather Melastome growth and other data to refine survey frequencies and estimate detection probabilities. This project also develops and reports on indicators of progress towards eradication based on field data from control teams.

Clidemia was previously the target of national eradication programs but is considered not eradicable and so has transitioned to a containment program. While clidemia research has concluded, apart from a seed longevity trial, this project continues to provide technical advice to staff and stakeholders implementing the containment program.

This project also supports field operations by investigating the time to maturity of the eradication target white ball acacia (Prohibited Matter), which is also concluding.

Research on weed seed dynamics

Project Leader: Simon Brooks

Information on the seed ecology of priority weeds across north Queensland will indicate how long weed control sites need treatment, providing there is no further seed input. Testing has been completed on chinee apple, calotrope, Captain Cook tree, neem tree, mesquite, yellow bells, lantana, leucaena, parthenium, sicklepod and gamba grass. Assessments of the seed longevity of sagittaria, prickly acacia and harrisia cactus are still running and more species may be added. To provide further evidence of their seed longevity, seedling emergence studies have been implemented for chinee apple, leucaena, prickly acacia, mesquite, elephant ear vine and neem tree. This project is also comparing seed longevity based on field burial conditions with a shorter ageing test conducted in the laboratory. Additional experiments are being planned to determine the effect of temperature and soil depth on weed seed germination and elucidate emergence triggers.

Encapsulated herbicide control of woody weeds

Project Leader: Simon Brooks

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. Three field trials commenced in 2021-22 and a further three are planned in 2022-23.

Real-time, drone-based, parthenium weed identification for improved pasture management

Project Leader: Olusegun Osunkoya

The project aims to identify weeds using drone-based imagery processed using machine learning. We will demonstrate this capability with identification of parthenium (Parthenium hysterophorous) - an annual Weed of National Significance costing millions of dollars in control and lost production in Australia.

The problem will be addressed in two steps:

Step 1 is to significantly improve the object identification of parthenium in the field using high resolution drone images and improved deep learning algorithms.

Step 2 is to live stream the high resolution drone video to the base (i.e. ground), then carry out the out weed recognition on a field computer in real time

Impact and management of Navua sedge

Project Leader: Olusegun Osunkoya

There are few quantitative data on the yield loss to the grazing/cropping industries caused by Navua sedge. We have established research plots in eight grazing sites in far north Queensland infested with Navua sedge. Within these experimental plots, we identified high-medium-low infestation subplots and quantified pasture diversity and soil seed bank composition. In the plots with different Navua sedge infestations, we will impose grazing and herbicide treatments, and again survey the plots to quantify yield loss, changes in above-ground biomass of desirable plants, changes in soil seed bank composition and changes in soil biochemistry.

In 2021-2022, we used questionnaires to gauge the economic loss caused by the weed to impacted graziers of the Atherton Tablelands. In 2022-2023, we will extend the questionnaire to other stakeholders in northern and far northern Queensland.

Risk assessment for new and emerging invasive weeds

Project Leader: Olusegun Osunkoya

Given limited funding, it is important that new and emerging weeds are continually identified, ranked in terms of likelihood of spread and impact, and feasibility of management. The most recent assessment of risk for new Queensland weeds was in 2013. This project will assess the risk of >200 emerging weed species in Queensland using the published literature, unpublished reports and field experience of pest managers. The project will also the assess the determinants of invasiveness including biotic (e.g. species traits) and abiotic (e.g. environment) influences.

Aquatic weeds of northern Australia – ecology and control

Project Leader: Melissa 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 Amazon frogbit (Limnobium laevigatum).  This project addresses ecological questions to improve management of current infestations and predict further infestations.  Control options will also be investigated.

Specifically, research will investigate:

  • Seed and vegetative reproduction abilities in regional populations of Hygrophila.
  • Herbicide control of bogmoss.
  • Seed viability and longevity in regional populations of Amazon frogbit.
  • Seed viability and longevity in regional populations of Aleman grass.

Sicklepod ecology and control

Project Leader: Melissa 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, road and power corridors and creek banks. It degrades riparian zones and pasture systems reducing biodiversity and beef production. In this project we aim to improve management tools for sicklepod by investigating: seed production and longevity, pre-emergent herbicide efficacy, and low-volume-high-concentration herbicide application techniques.

Efficacy of foliar herbicides on Aleman grass (Echinochloa polystachya) and Nemo wetting agent for broad application in aquatic situations

Project Leader: Stephen Setter

The 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 Far North Queensland Regional Organisation of Councils. The trial will initially investigate effective herbicide and wetter rates for the control of Aleman grass in field situations. If successful, the findings will support an application to the Australian Pesticides and Veterinary Medicines Authority for a minor use permit for Aleman grass control. If the herbicide trial is inconclusive or unsuccessful, an application for additional screening will be lodged. 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.

Improving pest control activities through timely submission of permits

Project Leader: Joe Vitelli

The project will facilitate chemical registration and permit applications for pesticides for the control of invasive species by Queensland pest managers. 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 seamless renewal and extension of permits.

There are currently 51 minor or emergency use permits issued to Biosecurity Queensland by the APVMA and a further seven permits issued to other states that Biosecurity Queensland sought inclusion to allow the control of declared and emerging weeds found in Queensland.

Red witchweed eradication

Project Leader: Joe Vitelli

Red witchweed (RWW) is a national eradication target having received high acclaims on its progress from an external audit in 2018.  An integrated control study was initiated in 2014 in the sugarcane-growing area of Habana, to investigate the efficacy of agronomic practices for depleting the RWW seed bank and preventing further seed production over a 10-year period. Pre- and post-emergent herbicides were applied to sugarcane and are being compared with catch crops, trap crops and fumigants. Additional trials have been established at the Ecosciences Precinct to determine whether seed depletion of RWW can be accelerated even further with a continuous false host soybean crop, punctuated with multiple applications of the fumigant ethylene.

Management of giant rat’s tail grass using wick wipers

Project Leader: Joe Vitelli

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.

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 and timing of grazing pressure but a limited understanding on how to use both glyphosate and flupropanate 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 wick wipers.

Management of sticky florestina

Project Leader: Wayne Vogler

Sticky florestina (Florestina tripteris) is an annual plant from semi-arid North America that was introduced to central-western Queensland anecdotally in the 1960s and reported as a pest in the late 1980s. Local governments are reporting a current profusion of the weed along roadsides. There is considerable scope for further spread of the weed as seeds are readily spread by livestock, wildlife, machinery and along waterways. The project is conducting research to improve control and management outcomes of this invasive weed.

Strategic invasive grass control to reduce the risk of further invasion in northern Queensland

Project Leader: Wayne Vogler

Gamba grass, grader grass and giant rat’s tail grass are serious invasive weeds in northern Australia resulting in large scale environmental damage and economic loss. The project will engage with a wide range of land managers including local government, indigenous, conservation and agricultural land managers to identify and control or eradicate strategic outlier infestations of these grass species on both privately and publicly-owned land.  These outlier infestations are early invasion populations of these invasive grasses that, if not controlled, will become established and provide a continuing source of seed for further invasion. Control of these early invasion populations will reduce the risk and rate of spread of these grasses and future detrimental impacts to the environment and agricultural production.