Weed Science Research Group

The Weed Science Research Group conducts research in the areas of integrated weed management, herbicide resistance, weed ecology and crop-weed interactions in Australian agricultural systems.

Research projects

Our research projects focus on agricultural weeds of concern to growers in Australian broad-acre farming systems. Our projects adapt and evolve according to our latest findings and the needs of the agricultural community. 

  • Crop competition for weed management and maintenance of crop yield

    crop competition project

    We investigate the integration of cultural weed control tactics with herbicides to improve crop competitiveness against weeds across different rainfall zones in the southern and western grain growing regions.

    Our research will help determine the stability of the performance of different weed control tactics against ryegrass, brome grass and wild radish across the different rainfall zones and regions.

    This GRDC-funded project is undertaken collaboratively with farming systems groups in the southern and western regions, enabling rapid transfer of project outputs to growers and advisers.

    Project goals
    • Quantify the effect of combinations of crop competition factors on weed seed-set and crop yield; and
    • Refine strategies and improve crop competitiveness across different rainfall environments in the southern and western regions of Australia.
    Crop species in focus
    • Southern region: wheat, barley, canola and faba bean
    • Western region: wheat, canola and narrow leaf lupins
    Weed species in focus
    • Ryegrass
    • Brome grass
    • Wild radish
  • Management of annual ryegrass in the high rainfall zone (HRZ)

    HRZ Crop Walk

    Annual ryegrass can be particularly challenging to manage in the high rainfall zone (HRZ). Widespread resistance to post-emergent herbicides used in cereals means there is strong reliance on pre-emergent herbicides for ryegrass control.

    Annual ryegrass seed banks in the HRZ tend to be high and there is late emergence of weeds due to the long and cool growing season. These late emerging plants contribute to high seed set that maintains populations.

    As a result, ryegrass populations quickly rebound when management is reduced. Late maturity of cereals means that 50% or more of the ryegrass seed can be shed prior to harvest, reducing the efficacy of harvest weed seed controls. On the plus side, moderate populations of ryegrass (<100 plants per m2) have less impact on yield than they do in other regions.

    High Rainfall Zone PortalProject goals

    This project aims to demonstrate annual ryegrass management strategies in the HRZ, providing confidence for agronomists and growers to make on-farm management changes that are effective and profitable.

    Project sites
    • 5 demonstration sites are established across southern Victoria and the south east of South Australia.
    • Sites are sown to wheat in 2019, with break crops in 2018.
    • Each site has 4 annual ryegrass management strategies of increasing management intensity, to demonstrate strategies that may provide effective and profitable management of annual ryegrass in the HRZ.
    • The management strategies employed at each site have been developed with local agronomists.
    • There will be opportunities to view the sites during the season.
    • Plot plans, treatments and data collected at each site is available via the HRZ ryegrass management portal.
  • Mechanisms, evolution and inheritance of resistance (Concluded)

    Broadleaf weeds

    Herbicide resistance in weeds limits the options available to growers to control weeds in an efficient and cost-effective manner, making them a major threat to profitable grain production systems in Australia. Herbicide resistant weed populations have been discovered throughout Australia including in grain crops, fallows, orchards, vineyards, fence lines and irrigation channels. This project is concentrating on key existing and emerging weed resistance issues of importance to Australian grain growers.

    We investigate:

    • The biochemical and molecular mechanisms involved in resistance, such as target-site mutations, reduced translocation of herbicides throughout the plant, gene amplification and rapid necrosis.
    • How selection for herbicide resistance mechanisms occur in the various weed species and populations.
    • The evolutionary dynamics of herbicide resistance e.g. inheritance studies to determine the number and cross-resistance patterns of genes contributing to resistance.
    • The most effective approach to manage various herbicide resistance situations.
    Weed species and herbicide resistances in focus
    • Glyphosate resistance in brome grass, barnyard grass, sowthistle and feathertop Rhodes grass
    • Diflufenican and 2,4-D resistance in Indian hedge mustard
    • Phenoxy herbicide resistance in sowthistle
    • Clethodim resistance in ryegrass
    • Resistance to pre-emergent herbicides in annual ryegrass

    The knowledge gained from this project will underpin strategies to delay the onset of herbicide resistance and also to manage the impact of existing resistances, by informing appropriate rotations and sequences of herbicide applications as part of an integrated weed management strategy. Better herbicide choices by growers will delay the onset of resistance to key herbicides in their crop rotations.

  • Emerging weeds in Australian agricultural systems (Concluded)

    weed seed biology

    Weed populations are dynamic in nature and changes in farming systems, farm management practices and climate are resulting in a changing weed spectrum. Several weed species that previously were mainly weeds of pastures (e.g. barley grass) have now become significant weeds of crops, thereby increasing costs and reducing yields.

    Growers are seeking information about the behaviour of these emerging weeds, especially seed-bank persistence, in order to manage them effectively. At present such information on weed seed biology is not available for many of these weed species.

    Project goals
    • Review existing knowledge of seed dormancy, life-cycles and seed-bank persistence of identified emerging weed species.
    • Characterise 10 major emerging weed species in each of the northern, southern and western cropping regions of Australia, through field experiments and laboratory studies. To better understand weed seed biology our focus is on the following characteristics:
      • seed dormancy - especially the effect of climate and management practices on seed dormancy;
      • seed-bank persistence - build-up and depletion rates, effect of rainfall and depth of seed burial;
      • rate of seed drop (dispersal after maturity) and weed spread; and
      • competitiveness with crops.
    • Facilitate development of integrated weed management strategies by providing information on weed seed biology to decision support systems, growers, agronomists and consultants.
    Weed species in focus
    Grasses Other
    • brome
    • barley
    • windmill
    • liverseed
    • button
    • sweet summer
    • feathertop Rhodes
    • wireweed
    • sowthistle
    • wild turnip
    • bifora
    • roly-poly
    • caltrop
    • turnip weed
    • bladder ketmia
    • prickly lettuce
    • Afghan melon
    • marshmallow
    • Mexican poppy
    • Indian hedge mustard
    • bedstraw/cleavers
    • doublegree/three corner Jack
    • statice/sea lavender

    The knowledge about weed seed and seed-bank biology gained from this project will allow the development of effective control tactics, including integrated weed management strategies, for these emerging weeds.

    More information about the weed species that are emerging under current management systems will allow growers to make informed decision about their weed management programs in the future, enabling them to reduce the impact and costs of their weed problems.

  • Weed management in Australia’s southern region mixed farming systems: Strategies to combat herbicide resistance (Concluded)

    herbicide resistance strategies

    We develop effective non-chemical and chemical management tactics for strategic use against particular weeds. We also explore the implementation of cost-effective weed management in mixed cropping systems with pasture rotations. This research will prove critical in limiting the spread of new and emerging weed species and slowing the development of herbicide resistance(s).

    Weed infestations result in significant costs to both continuous cropping and mixed farming producers across southern Australia, both in terms of crop productivity and also livestock health and productivity.

    Changes in weed species spectra and their biology is reducing the efficacy of previously successful weed management strategies. As weeds adapt to changing farming practices evolution of herbicide resistances and weed species shifts occurs, both of which are threatening the continued success of conservation farming systems across the southern region.

    Project goals
    • Assess and address the impacts of major weeds in continuous cropping and mixed farming systems across southern Australia.
    • Evaluate management practices that will be appropriate for controlling weed species in a changing environment where herbicide resistance is problematic.
    • Develop effective management strategies to combat herbicide resistance while maintaining the benefits of conservation farming.

    Led by Professor Leslie Weston from Charles Sturt University, our group is primarily involved with broadacre cropping systems across South Australia and Victoria, and will concentrate on:

    • Surveys of herbicide resistance in key weed species.
    • Research trials for weed epidemiology with a focus on strategic management of 3 key weed issues:
    • Annual ryegrass management in high rainfall zones
    • Management of clethodim resistant weeds in rotations with high frequencies of break crops
    • Management of imidazolinone resistant brome grass in cereal rotations
    • Identifying new solutions for major weeds in continuous cropping no-till systems, towards development of new knowledge on chemical management strategies and use patterns.
    Weed species in focus
    Grasses Broadleaf Other
    • Annual ryegrass
    • Barley
    • Brome
    • Wild oats
    • Indian hedge mustard
    • Sowthistle
    • Wild radish
    Other weeds found to be present at high frequencies.

    Knowledge gained from this project will result in the development and demonstration of new and effective chemical and cultural management strategies for major weeds in the southern grains and mixed farming region. Findings will assist growers to optimise their weed control tactics in the context of continued profitable no-till farming practice and to also consider the potential of integrating a profitable livestock enterprise.

  • New uses for existing chemistry (Concluded)

    Seeding pass

    Herbicide resistance is a major problem in Australian grain cropping, reducing the herbicide choices available to growers and increasing their costs. There is a need to increase the availability and flexibility of controls for herbicide-resistant weeds, including new herbicide uses.

    Worldwide, Australia is a small market for agrichemicals and new herbicides typically remain unregistered despite gaining registration in other countries.

    Project goals
    • Develop data to facilitate and promote registration of new uses for existing herbicides
    • Identify new uses for existing registered pre- and post-emergent herbicides
    • Register these new uses on herbicide labels or permits
    • Broaden the choice of herbicide uses available to growers

    This project is led by Dr Bhagirath Chauhan from the University of Queensland and our group will primarily concentrate on pot experiments and field trials targeting identification of herbicides that are able to control brome and barley grasses.

    Weed species in focus
    • Barley grass
    • Brome grass
    • Awnless barnyard grass
    • Feathertop Rhodes grass
    • Fleabane
    • Sowthistle
    • Wild radish

    Knowledge from this project will make available new herbicide treatments for site-specific management of crop weeds. It will provide growers with more options when tackling problem weeds including those with herbicide resistances.

Our research is supported by and affiliated with: