Make every drop of herbicide count
For ten years, WeedSmart has stood alongside growers and agronomists, promoting science-backed practices known to drive down the weed seed bank and stave off the threat of herbicide resistance.
To mark this milestone, the WeedSmart team and our research partners have reviewed the WeedSmart Big 6 tactics and made a few modifications, including the addition of ‘Optimise spray efficacy’.
Dr Ken Flower, director of the Australian Herbicide Resistance Initiative and Dr Chris Preston, Professor, Weed Management at The University of Adelaide, contributed to the review to highlight the importance of ensuring that ‘every drop of herbicide applied counts’.
“Herbicides are an essential component of broadacre grain and cotton cropping systems in Australia, and the decisions growers make around herbicide use and application have long-term effects,” says Dr Flower. “The fine-tuned WeedSmart Big 6 provides growers and agronomists with key guideline principles to use when making critical decisions about what is applied and how each spray job is done.”
Before herbicide selection has taken place, it is very rare for an individual weed to be resistant to two herbicides. Mixing herbicides at full label rates in a single application takes advantage of this fact.
Within an integrated weed control program, try to make sure there is herbicide rotation and mixing going on in each phase – in the fallow, pre-seeding, in-crop and for desiccation. When done with a determination to stop seed set and remove survivors, it is possible to keep weed numbers low.
Following resistance-prone herbicides with another tactic to control survivors in a fallow or pre-sowing situation and prevent weed seed set will keep more herbicide options available well into the future.
Herbicide resistance testing is the most cost-effective way to know what herbicides will and won’t work in a particular paddock.
“Low-dose applications increase the chance of weeds developing herbicide resistance, and there are several ways a weed can receive a low dosage of herbicide,” says Dr Flower. “All herbicides must be applied at label rates, with attention given to delivering the full, effective dose to unstressed weeds, in suitable environmental conditions and with the sprayer set up correctly to maximise efficacy and reduce spray drift.”
“Experienced and careful sprayer operators will pay attention to mixing partners, water quality and droplet size, as well as environmental conditions at the time of spraying.”
Further resources
GRDC Podcast, 10 years of WeedSmart and the ‘Big 6, with WeedSmart extension agronomists Jana Dixon and Greg Condon
