Adoption of integrated weed management increases cropping system resilience to new weed incursions and resistance

Weeds cost Australian crop growers over A$3B annually in lost yield revenue and expenditure on controlling existing weeds. The invasion of a new weed species or new forms of herbicide resistance can add to this cost when they are not readily controlled by existing practices. An additional and potentially under-recognised benefit of integrated weed management (IWM) strategies aimed at preventing seed-set and increasing weed suppression could be to minimise the cost and spread of unexpected new incursions or forms of resistance, thereby restricting further spread across cropping regions. We quantify the additional cost of gaining a resistant weed incursion into a field (e.g. through weed mobility) and assess the relative value from having a diverse IWM program already in place. The RIM-model was used to evaluate the costs of gaining glyphosate-resistant annual ryegrass in a winter cropping system. Scenarios examined glyphosate-resistance risk with/without IWM practices on a common crop rotation in the Riverina and Sunraysia/Mallee regions of southeastern Australia. Modelling results reveal that the size of weed seedbank and the cost of gaining glyphosate resistance in these contexts were less when more diverse weed control practices and competitive crops were used. IWM increased resilience to the incursion of the new form of resistance by reducing the cost of controlling resistant weeds by 80%. This study highlights the potential fo value from investing in diverse IWM to achieve effective management of existing weeds, while reducing costs and risks from new resistance and weed introductions. Based on weed seed production results, the practices are likely to reduce the risk of a potentially mobile new weed type spreading at the paddock, farm, and landscape scale. The potential for this additional risk reduction and resilience benefit is deserving of additional consideration when evaluating the value of investing further in diverse IWM strategies.

Monjardino, M., Islam, M., & Llewellyn, R. (2024). Adoption of integrated weed management increases cropping system resilience to new weed incursions and resistance. Proceedings of the 23rd Australasian Weeds Conference Brisbane August 2024., pg195. https://acrobat.adobe.com/id/urn:aaid:sc:AP:24e14be0-0ebf-450d-8433-5b3c7fd07a45?viewer%21megaVerb=group-discover