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Two sprays tackle stacked resistant radish


Treating wild radish (Raphanus raphanistrum L.) early in the growing season in the northern wheatbelt as part of a two-spray strategy – using robust herbicide rates and excellent application – can boost wheat yields by 0.5-1 tonne/hectare.

That is a key finding from large-scale 2013 trials initiated by the GRDC’s Geraldton port zone Regional Cropping Solutions Network (RCSN) and run by Grant Thompson (pictured), of Crop Circle Consulting.

The research was carried out at sites in Northampton, Casuarinas and Chapman Valley and aimed to:

  • Develop herbicide solutions and sequences that avoid using the same product twice in a single growing season
  • Get herbicide timing and application rates right
  • Delay the onset of wild radish resistance to – and prolong the efficacy of – new actives pyrasulfotole (Group H – eg. Velocity® and Precept®) and pyraflufen-ethyl (Group G – eg. Ecopar®)
  • Develop a best practice management guide for control of wild radish with multiple herbicide group resistance.

Wild radish in flower

Herbicide resistance in wild radish

There is an increasing threat of multiple herbicide group resistant wild radish and ‘stacked’ resistance in the northern wheatbelt.

In this region, there is already widespread wild radish resistance to herbicides such as SU’s, diflufenican, MCPA and 2,4-D amine.

Newer registered chemicals, such as pyrasulfotole and pyraflufen-ethyl are highly effective at controlling radish.

But there is industry concern about repetitive use of these products and a need to prolong their effectiveness.

The value of older herbicides

In the first year of GRDC’s RCSN- funded wild radish control trials in the northern wheatbelt in 2012, Peter Newman – then with the Department of Agriculture and Food WA (DAFWA) and now a consultant with the Australian Herbicide Resistance Initiative (AHRI) and Planfarm – demonstrated older herbicide groups could still be effective against wild radish.

The keys to success were:

  • Targeting weeds when small – about the size of the top of a beer can
  • Using a timely two-spray strategy with a quick and timely second spray
  • Ensuring herbicide rates are robust
  • Using correct water volumes, nozzles and speed.

For the 2013 trial results and observations, read on here

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