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Group I Herbicide Resistance in Wild Radish …… So, What’s Our Strategy?

Herbicide resistant wild radish is a developing issue within Victorian cropping systems. While resistant Wild Radish populations have been present in areas of Western Australian cropping regions for some time, similar resistance has now crept into Victoria. Chris Preston, in conjunction with University of Adelaide, first detected resistant populations in the Hamilton region around 5 years ago. 

 

Further to these findings, last year an incidence of poor Wild Radish control in a wheat paddock near Hamilton sprayed with a Group FCI herbicide prompted Western AG to send samples for resistance testing to Plant Science Consulting. Results indicated a 40% resistance to Group I phenoxy chemistry (MCPA) and 10% resistance to the Sulfinoamide (Eclipse) subgroup of Group B herbicides.

Photo 1. Resistant wild radish biotypes versus non-resistant check to LVE MCPA. Photo courtesy of Plant Science Consulting P/L

Historically in the Hamilton region, tank mixes for wild radish control in wheat have consisted of LVE MCPA (Group I), Ally (Group B) and Tigrex (Group F and I) so, whilst a result showing 40% resistance to Group I isn’t surprising, this is cause for concern. Resistance levels at this percentile are considered weak, however spray efficacy is still impacted as plants can recover by the development of new shoots and if left unchecked further resistance could occur rapidly.

 

To combat this ever-increasing issue, Western AG are recommending application strategies to ensure that Wild Radish populations are not surviving through sublethal doses by adopting a two-spray approach taken to Wild Radish control. Ensuring that target plants are small, using products that contain multiple chemical groupings and using top label rates are all suitable tools that need to be used to ensure effective control of Wild Radish in crop.  

 

Overall, when it comes to Wild Radish resistance, a “take no prisoners” mentality is critical to ensuring populations are managed at every opportunity with timely applications to minimise the reintroduction of resistant seeds back into the seedbed. A lack of control now could result in a major issue that is very difficult to control in the future, as what has happened in Western Australia. The Western AG Agronomists will be partnering with growers to carry out further testing over the coming months to determine resistance levels on a property level so that appropriate control can take place to stop the spread of resistant seeds. Further information on these findings will be shared later in the year. If you have any concerns about Wild Radish resistance on your farm, please contact your Agronomist to have a resistance test sent to Plant Science Consulting.
 

 

Article produced by - Claudia Higgins, Western AG Hamilton