Glyphosate is the most important herbicide used in agriculture in Australia. However, glyphosate is coming under threat from market concerns, particularly some premium markets in Europe, and from the emergence of glyphosate resistant weeds. This project was conducted to increase awareness among the grain production community in South Australia of the problem and to explore potential alternative practices. Seven field trials were conducted across 2022 and 2023 at Wangary, Minnipa, Hart, Struan and Gawler to examine the potential for glufosinate mixed with Group 14 herbicides and other strategies to replace glyphosate for pre-sowing weed control. Glufosinate-based alternatives to glyphosate can be as effective at pre-sowing weed control, but will be considerably more expensive. The dry sowing trial at Gawler demonstrated the benefits of selecting effective pre-emergent herbicide strategies for dry sown wheat. A video was produced including farmer tips for successfully adopting harvest weed seed control on the farm. Discussion surrounding the project has increased the awareness of farmers and farm advisors of the need to protect glyphosate from loss due to resistance. The project also increased discussion within the agrichemical industry of potential replacements to glyphosate.
Project description:
Glyphosate is the most important herbicide used in agriculture in Australia. However, there are market concerns about glyphosate use in the growing of agricultural products, particularly some premium markets in Europe. In addition, glyphosate usefulness is decreasing due to the emergence of glyphosate resistant weeds. There are two key uses of glyphosate in grain crop production in South Australia. These are application prior to sowing the crop and the practice of crop-topping, using glyphosate once the crop is mature to reduce seed production of weeds. This project was conducted to test a previously published synergy between glufosinate and Group 14 herbicides as a potential replacement for glyphosate in weed control prior to sowing the crop.
A set of 5 demonstration trials were conducted to test rates of glufosinate and two recently registered Group 14 herbicide products for control of weeds prior to sowing. An additional trial examined double knock approaches, using two herbicides within 14 days to control glyphosate resistant weeds and improve weed control. The final trial tested strategies for weed control in dry sowing of wheat, which can avoid using glyphosate.
The demonstration trials showed that it was possible to replace glyphosate use with other strategies and achieve equivalent weed control. However, these other strategies require the use of higher rates of glufosinate and Group 14 herbicides making them considerably more expensive than the use of glyphosate alone. Using glufosinate and a Group 14 herbicide as the first component of a double knock strategy was also effective. In the dry sowing demonstration trial at Gawler the use of a pre-emergent herbicide followed by an early post-emergent application of Mateno Complete was the most effective strategy to manage annual ryegrass in dry sown wheat.
There were 6 crop walks and a field day at the trial sites with 337 farmers, farm advisors and industry participants attending. In addition, the project has developed a podcast with a local agronomist discussing strategies of managing glyphosate resistant weeds in the high rainfall zone. A video featuring a South Australian farmer discussing the benefits and practicalities of harvest weed seed control and how the practice is used on their farm. A fact sheet was developed to more broadly disseminate the learnings from this project.
The main beneficiaries of this work will be farmers who should have more confidence in adopting practices to replace glyphosate in their farming systems if necessary. The increased interest by the agrichemical industry in exploring solutions to pre-sowing weed control could lead to additional choices for farmers in the future.
The dry sowing pre-emergent herbicide strategies can be adopted now by farmers who regularly use dry sowing. The increased knowledge of farm advisors about effective weed control strategies or dry sowing wheat should aid adoption by farmers. The increased costs of the glufosinate and Group 14 herbicide strategies compared to glyphosate will be a barrier to adoption so long as glyphosate is available and effective. However, should glyphosate resistance continue to increase in South Australia or glyphosate be unavailable for market reasons, these strategies may become more attractive.
Key achievements and results:
- While effective pre-sowing weed control strategies exist as alternatives to glyphosate, their current cost is significantly higher.
- Mixtures of glufosinate and Group 14 herbicides, along with other strategies, can achieve equivalent weed control to glyphosate in many cases.
- Dry sowing practices offer a viable option to reduce the need for pre-sowing herbicides, especially when combined with effective pre-emergent herbicide selection.
- Early post-emergent applications of Mateno® Complete proved effective in managing weeds emerging after dry sowing.
- Widespread adoption of these alternative pre-sowing strategies and dry sowing practices can help conserve glyphosate for future use.
Benefits to industry
- Preserves glyphosate: By developing and adopting alternative strategies, growers can prolong the effectiveness of glyphosate, ensuring its continued viability as a crucial tool for weed control.
- Minimises disruption: Having readily available alternatives minimises potential disruptions and allows for immediate adoption if glyphosate is ruled out due to resistance issues or market demands.
- Future sustainability: Ongoing research and development efforts by agrichemical companies hold promise for more cost-effective and sustainable solutions.
Recommendations for growers
- Implement effective pre-sowing weed control strategies as an integral part of your farm’s weed management plan.
- Consider dry sowing practices, especially when combined with strategic selection of pre-emergent herbicides, as a viable option to reduce reliance on pre-sowing herbicides.
- Include early post-emergent applications of registered products for effective weed control in dry-sown crops.
- Partner with agricultural advisors to develop a tailored weed management plan specific to your farm and crop rotation.
- Actively participate in research trials and demonstrations to stay informed about new weed control technologies and best practices.
DISCLAIMER
Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the South Australian Drought Resilience Adoption and Innovation Hub (SA Drought Hub). No person should act on the basis of the contents of this publication without first obtaining specific, independent, professional advice. The SA Drought Hub and contributors to this publication may identify products by proprietary or trade names to help readers identify particular types of products. The hub does not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred to. The SA Drought Hub will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication.
Further information:
Project Images
Effect of knockdown herbicide treatments on weed growth 14 days after application at Hart in 2022. From left to right: untreated; glyphosate + Hammer®; Liberty® + Voraxor®.
Effect of knockdown herbicide treatments on weed growth 14 days after application at Hart in 2023. From left to right: untreated; glyphosate + Hammer®; Liberty® + Terrad’or followed by paraquat.
Annual ryegrass populations present at the dry sowing trial at Gawler in 2023. Left: Nil; Right: Overwatch® followed by Mateno® Complete.