Wild Radish Control: Understanding the Seedbank and Resistance Management

Cameron Taylor, Birchip Cropping Group (BCG)
Peer reviewers: Harm van Rees (Cropfacts) and Simon Craig (Agronomise)

Background
From BCG wild radish research trials over the last three years, it is evident that populations are currently in a state of flux, with more incidences of resistance to herbicide Groups B, F and I emerging across North West Victoria. Much of this has been attributed to a heavy reliance on Group B herbicides to control grass weeds such as brome and rye grass. The consistent use of MCPA ester and amine formulations (Group I) is resulting in the effectiveness of these products diminishing. Subsequently the selection pressure being placed on these herbicides is increasing.
A radish plant can produce up to 5000 seeds which, due to the hard-seeded nature of the pods, can stay in the top soil for up to eight years without germinating. The plants are highly competitive and when present in high numbers can greatly affect crop yields. This is the reason such importance has been placed on controlling 100 per cent of wild radish every year.
In 2014 BCG carried out research trials to help growers understand the life cycle of wild radish in the Mallee and to identify methods that decrease the radish seed bank in problem paddocks. Adopting practices that help to reduce the number of viable weed seeds present in the seed bank (predominantly by preventing new plants from setting seed) improves the productivity of the paddock and decreases the need for costly herbicides, delaying the onset of further herbicide resistance.