Australian grain growers know all too well that there is no quick fix when it comes to weed control. Rather, a range of strategies are usually needed to overcome what is one of the most challenging threats to profitable production.

The WeedSmart team has honed its ‘Big 6’ strategies over a decade, presenting growers with a practical, science-backed toolbox to combat weeds and reduce the risk of herbicide resistance.

WeedSmart is an industry-led initiative, supported by GRDC in partnership with agricultural companies and research institutions whose objective is to share and build weed-control knowledge.

At its 11th annual WeedSmart Week event held this year in Port Lincoln, SA, close to 300 delegates heard from more than  20 growers, agronomists and researchers based in and around the Eyre Peninsula about the latest in weed control and how they are using the Big 6.

Jana Freebairn, an agronomist based in SA’s Lower North, is one of five WeedSmart extension agronomists located across Australia. She told attendees that in 2023, the Big 6 had been revamped to reflect the importance of using herbicides appropriately to maximise their efficacy. ‘Optimising spray efficacy’ is now a pillar tactic with a tagline  to ‘make every droplet count’.

Ms Freebairn said it was important to highlight best practice herbicide use to optimise effectiveness and reduce the development of resistant weeds. Reducing spray drift was also important from a stewardship perspective to prevent off-target damage, she said.

“A lot of direct weed control is achieved through herbicides, but spraying in the wrong conditions, with the wrong tank mixes or with the wrong application methods, can contribute to herbicide resistance,” she said.

Using the right product at the right time and applying it correctly to make sure that every droplet you spray hits the target will maximise the results. It’s such a critical component of weed management that we want to highlight  it as a tactic within the Big 6 strategy.

Systems approach

But Ms Freebairn said that a robust herbicide program is only one part of the weeds management picture.

By taking a “whole-of-farm” approach using multiple tools, you could build a farming system that works to suppress weed numbers over the long term, she said. “‘Don’t look at weeds in isolation’ is a key WeedSmart message.”

Ms Freebairn encourages growers to consider the issues that may have led to a particular problem – such as soil health, poor crop competition or poor control of seed-set in previous years – and then how to build a rotation and a farming system to counter this.

Along with optimising spray efficacy, the other five pillars of the Big 6 involve rotating crops and pastures, increasing crop competition, mixing and rotating herbicides, stopping weed seed-set and implementing harvest weed seed control.

Ms Freebairn said weed prevention strategies need to be part of all major decisions, from equipment choice to crop choice, timing of sowing, harvesting, fertiliser inputs and soil amelioration.

The importance and breadth and unceasing challenge of weeds management was reflected by the strong turnout of growers, consultants and industry representatives from across the region, the state and the country at WeedSmart Week.

First-hand insight

WeedSmart project manager Karen Smith said the event provided opportunities for growers to hear about science-backed solutions to “weed out” herbicide resistance and find pathways to adopting control measures on-farm.

Panel sessions involving growers from the Eyre Peninsula (EP) discussed applying the Big 6 in farming systems, opportunities around introducing legumes into crop rotations, destroying weed seed with  impact mills and automated spot spray application technology.

Ms Freebairn said it was fascinating to hear first-hand from growers on the EP about the technology they are already using, such as drones, to target specific weeds: “It’s almost come about from necessity with conditions getting too wet for ground rig sprayers and people are now using drones to not only map weeds but spray them as well.”

WeedSmart Week participants also visited on-farm sites to see first-hand the impact of subsurface paddock drainage on timely operations and how a rock-crushing Reefinator machine can improve crop production in rocky paddocks. Both tactics are helping to suppress weeds through better crop establishment and vigour.

New technology was also on show as part of a machinery expo, including weed seed impact mills and camera-assisted ‘green-on-green’ automated spot spraying to target weeds in-crop.

Ms Freebairn said technology targeting specific weeds was an exciting development in weed control that would lead to more profitable businesses.

If you are reducing your herbicide usage through ‘green-on-green’ spraying technologies, you can use more expensive herbicides in smaller amounts to achieve better weed control, she said.

Ms Smith said WeedSmart Week was held in a different growing region each year, providing opportunities for participants from around the country to learn from one another in their common fight against weeds.

In 2025, WeedSmart Week will be held in August in Geraldton, WA.

More information: Karen Smith, karen.s.smith@uwa.edu.au, weedsmart.org.au