Resistance to herbicides in the broadleaf weeds Raphanus raphanistrum, Sisymbrium orientale and Sonchus oleraceus as determined by random weed surveys in southeastern Australia.

John Broster; Peter Boutsalis; Gurjeet Gill; Christopher Preston

Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Resistance to herbicides in the broadleaf weeds Raphanus raphanistrum, Sisymbrium orientale and Sonchus oleraceus as determined by random weed surveys in southeastern Australia.

John Broster , Peter Boutsalis, Gurjeet Gill, Christopher Preston

Abstract

Context. Broadleaf weeds infest crops and reduce crop yield. The use of herbicides to control these weeds results in the evolution of herbicide resistance. Aims. There is limited information about the extent and distribution of herbicide resistance in for three key broadleaf weeds of this region. broadleaf weeds in southeastern Australia, so a survey was conducted to provide this information Methods. A survey of three broadleaf weeds of grain crops collected Raphanus raphanistrum, Sisymbrium orientale and Sonchus oleraceus across southeastern Australia between 2013 and 2017. Samples were screened for resistance to commonly used herbicides. Key Results. In all, 1760 fields were visited with 74 R. raphanistrum, 95 S. orientale and 488 S. oleraceus seed samples collected. Resistance to the ALS-inhibiting herbicide chlorsulfuron was most common in these species, present in 66% of S. oleraceus, 34% of S. orientale and 17% of R. raphanistrum samples tested. R. raphanistrum and S. orientale also had samples resistant to atrazine, diflufenican and 2,4-D. No resistance to glyphosate was found in any species. Multiple resistance to two or more herbicide modes of action was present in all three species. Conclusions. Herbicide resistance was identified in all three weed species in all the states where they were collected. All species had resistance to more than one herbicide mode of action. Implications. While the frequency of resistance in these broadleaf weeds in southeastern Australia is low to most herbicides, the accumulation of multiple resistance means that alternative management strategies will be required to effectively manage these weeds.

CP25041 Accepted 19 May 2025