More Velocity® resistant radish – but we can control it with mixes

Written by: Pete Newman

“She’ll be right mate, that radish isn’t resistant, it was just the ….”


Spray application

Weed size

Dud batch of chemical


Not enough sun

Too much sun

We’ve become accustomed to wild radish dying in our cereal crops these days with a number of reliable products now on offer.


Resistance testing by Dr. Roberto Busi at AHRI is now starting to find a number of Velocity® resistant wild radish populations.


The good news is that they can be controlled, it just takes the right mix.

Yes, we sound like a broken record, but mixing herbicides is such an important message and the results speak for themselves.

In his most recent research, Roberto’s team tested 376 wild radish populations to 21 herbicides and mixes over four years, finding that wild radish can always be controlled with three or four herbicide modes of action in the mix.

If you see surviving wild radish, don’t make excuses, come back with a robust mix, and prepare to take a resistance testing sample so you know what you’re dealing with.

This research was a massive effort. Growers and agronomists took 376 wild radish samples from paddocks where resistance was suspected, and Roberto Busi and his team at UWA tested each sample with 21 herbicides and mixes.

That’s 7199 individual resistance tests, screening 104,000 individual seeds and seedlings.


This is where the samples came from.


The results are summarised in the table below. There’s a lot of numbers here so I’ll narrow it down to the highlights.

There are high levels of resistance to 2,4-D, MCPA, Brodal (diflufenican), Picolinafen, Imi’s, and SU’s (e.g. Logran). Not so long ago this list of herbicides was all we had to fight radish with. Talk about taking a knife to a gun fight!

Then Velocity came along and we could kill radish again. But now we are starting to see resistance to this great product, with 15% of populations showing some level of resistance.  Often the resistance seen in pots is still low due to the well-known synergy between Group 27 (pyrasulfotole, topramezone) and Group 6 (bromoxynil).  But this low level resistance gives us an early warning of Velocity resistance so we can jump on it quickly in these paddocks.

And then a number of other mixes were developed, and somehow it turns out you can have levels of resistance to all of the mixing partners, but put them all in the same tank together and it works! See Quadrant below. Also check out Velocity + MCPA + Glocker.

And now we have a number of group 14 (G) products to which there is currently no resistance, giving us more in the arsenal.

Table 1: Resistance test results of 376 wild radish populations from Western Australia sampled over four years from 2019 to 2022. S = susceptible less than 5% survival, DR = developing resistance 6 to 19% survival, R = resistant 20% survival or greater


Modes of action in the mix

The next two graphs confirm that the more chemical modes of action you have in a mix, the better the chance of killing wild radish.

The first chart is the average wild radish kill rate with either 1, 2, 3 or 4 modes of action (MoA) in the mix. Average wild radish control increased from 85% with a single herbicide, to over 99% with a mix of four modes of action.

Figure 1: Average wild radish control (kill rate %) for 1 to 4 modes of action mixed in the tank.

The next chart shows the percentage of populations that tested as resistant as the number of modes of action in the tank increased.

Where only one mode of action was applied, less than 50% of populations tested as susceptible, with 27% of populations testing as resistant.

As we increase the number of chemicals in the tank, control increases with 93% of populations testing susceptible to mixes with four modes of action, and less than 1% of populations testing as resistant.


Figure 2: Wild radish resistance level to 1,2,3 or 4 modes of action mixed in the tank. Green = susceptible. Blue = Developing resistance. Red = resistant.


Resistance in wild radish has progressed, and so have the options to control these highly resistant populations. While we will start to see more populations that are resistant to quality products like Velocity®, at least we know that we can control these populations with a robust mix.  We need to keep confusing the weeds by tank mixing different modes of action and herbicide groups.   And if you see surviving radish, don’t make an excuse, assume it’s resistant and bring out the big weapons in your arsenal. Oh, and do a test as well, knowledge is power.


Herbicide Rates (for those of you looking for finer detail!)

Posted in: AHRI Insight, Resistance surveys

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