A Herbicide Resistance Guru. Helping growers combat herbicide resistance is what I do!
Adelaide, South Australia
Joined May 2016
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Good year for crop topping ryegrass in barley in the southern region, even if there is some glyphosate resistance in the paddock, still worth doing.
All 3 pots susceptible to Overwatch. Different rates of activity affected by the germination rate of different populations
Paraquat review finally out. Now try to summarise it!
apvma.gov.au/news-and-public…
Wild oat seedlings arrived in perfect condition for resistance testing. Grower testing Achieve, Axial, Atlantis & Hussar. Will have answer in 4 weeks.
More info that keeping atrazine & clethodim separated avoids antagonism. Here on DIM resistant ryegrass. The benefit of the 10 min split indicates chemical antagonism as it's unlikely there would be any biological effect in such a short time. SOA and 1% Hasten used. @WeedSmartAU
Something you don’t see often in ryegrass. Resistance to Paraquat at 1.2 and 2 L but not resistant to Glyphosate at 1 L.
Variation in DIM resistance in ryegrass. Higher clethodim rates can work. Adding Factor often better. From 500+ comparisons of clethodim resistant ryegrass, in 40% of cases, the addition of 180g Factor provided greater control. We can test this with the Quick-Test.
Peter Boutsalis retweeted
Combination of Clethodim + Roundup Ready Performance Liquid on ryegrass resistant to Dims, Glyphosate or both. Photo is of 12 populations. Each pot is a single population. The location of each pot in each tray is the same population.
Ryegrass from WA, SA, Vic and NSW chosen.
Peter Boutsalis retweeted
Plant Science Consulting tested Clethodim plus Atrazine as a tank-mix vs Clethodim followed by Atrazine spray immediately after on susceptible and Dim-resistant ryegrass. Used Hasten and SOA. Significantly better activity on resistant ryegrass when NOT tank-mixed.
Peter Boutsalis retweeted
Our replicated pot trials identified that tank-mixing Clethodim + Atrazine was antagonist vs. Clethodim alone or separating the mixes. The longer the separation the greater the control. We included 3 DIM-resistant and 1 susceptible ryegrass in the study. @WeedSmartAU
I don't think I have to explain the below too much for this ryegrass from 2025 season. This is what over reliance on herbicides can create, an absolute monster! Not much in-crop control. Perhaps Liberty? Heavy reliance on PRE and EPE plus crop topping/ Seed Terminator needed.
Peter Boutsalis retweeted
Thankyou to @WeedSmartAU & @grassrootsag for including me. We need to be clever to stay ahead of weeds and resistance and keep our key herbicides working effectively. I took home some good points from the other presenters, great to have access to this info!
A big thank to our presenters @CropDoctor54 @PBoutsalis @becsta1984 & attendees for today’s @WeedSmartAU webinar.
Clethodim is critical for ryegrass but warrants effort to stay effective. Peter, CD & Bec provided some key insights. Check the website for a recorded version.
We have a mystery wild oat sample to test for herbicide resistance. It arrived in a black post bag. The tracking Nr & barcode didn’t work. I called Australia Post & the only details they had was that it was sent on 27 Nov from Sydney. If the sender is on X can they contact me.
Peter Boutsalis retweeted
Declining clethodim efficacy in canola & pulse-based rotations can be addressed with increased diversity. Join Greg Condon & Chris Davey talking to @becsta1984 & @PBoutsalis to discuss strategies to slow clethodim resistance.
🎧 Register buff.ly/aX4tKhD
Seed volume (part 3). The more seed sent the less important dormancy is as don't have to wait for the majority of seed to break dormancy. More seed = quicker turnaround in testing. Germination of crop topped seed can be low or zero -> no resistance result @WeedSmartAU
