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Australian Herbicide Resistance Initiative (AHRI)

The significant weed science research stories of 2018

Written by: Jessica Strauss, Peter Newman, Cindy Benjamin, Kirrily Condon 

It’s been a big year for AHRI. Former AHRI Director, Stephen Powles retired from the position earlier in the year, with Professor Hugh Beckie from Canada taking on the role.  We also saw the opening of the GRDC-funded Agronomy Laboratory at the University of Western Australia. Research is at the core of what we do though and we didn’t do that in halves this year either! Not only did AHRI produce significant papers, but other weed science groups nationally also made important discoveries.

Harvest Weed Seed Control continues to see gains in uptake, with novel approaches like chaff lining seeing rapid uptake across Australia. Some more sinister discoveries took place this year too. Metabolic cross-resistance in ryegrass was confirmed in South Australia and glyphosate resistance in the Northern region was labelled as a ‘clear and present danger’.

But much like the Christmas holidays, you’ve got to take the good with the bad. As fun as catching up with friends and family over the holiday season is, you’re likely to have to endure hearing Mariah Carey’s All I want for Christmas is You several times before (and don’t forget on!) the big day of December 25.
While some of the discoveries in terms of herbicide resistance have been very concerning, it’s not all bad news, with HWSC, as well as other non-chemical approaches, like crop competition, contributing toward keeping all the tools in the weed control toolbox working.

In the last insight of the year, we’re wrapping up the most significant stories we’ve reported on for 2018 as an early present for you. Have a great holiday season and we look forward to you joining us for AHRI insight in 2019!

Spoiled Rotten – the sequel  

“We used to have to get up out of the shoebox in the middle of the night and lick the road clean with our tongues, eat half a handful of freezing cold gravel for dinner working 24 hours a day at mill and when we go home our dad would slice us in two with a bread knife. And you tell that to the young people of today and they won’t believe you.” – Monty Python – You can refresh your memory on this skit here.

Four years ago, we suggested in AHRI insight that farmers were spoiled for choice with five harvest weed seed control tools to choose from with a sixth in development. Well, a lot has happened since then. Back in 2014, we had a tow behind Harrington Seed Destructor and what we now call chaff lining was called windrow rotting.

We now have seven harvest weed seed control tools to choose from, so if farmers were spoiled for choice in 2014 they are absolutely spoiled rotten now!

We truly are spoiled rotten!

We thought it high time to update you on all of the choices that farmers have to choose from when it comes to HWSC along with what we now know about the cost of operating the various HWSC tools.

There’s now something for everyone!

“We used to have to get up in the middle of the night half an hour before we went to bed, check the weather on the internet, and go out into the freezing cold to burn narrow windrows, hold a firebug out the window of the ute until our arms fell off, and if the fire got away we had to call all of our neighbours and go and fight it. And you try and tell that to the young farmers of today and they won’t believe you”.

Learn more here.

Chaff lining…too good to be true?

How often do we hear comments like “you get what you pay for” or “it’s too good to be true”? Well, chaff lining just may be the exception to those comments.

Chaff lining has been on a rapid rise to glory in the Harvest Weed Seed Control (HWSC) scene over the past two seasons. A survey of WeedSmart subscribers showed the percentage of growers using chaff lining increased from 6% in 2016 to 26% in 2017.

Researchers would be stoked with this level of adoption, but the curious thing was that there was really no research data available specific to chaff lining. Adoption seemed to be based on grower experiences (much of which was shared on Twitter) and the fact that chaff lining is the cheapest HWSC tool to set up at $6.40/ha (compared with the next cheapest at $7.10/ha for chaff tramlining and $12.80/ha for chaff carts*).

*Figures sourced from AHRI Insight ‘Spoiled Rotten – the sequel’. Note the capital cost of chaff lining is based on a kit commercially available from Westoz Boilermaking, many growers are making their own kits at very low cost.

So, at $6.40/ha, do you get what you pay for? Is it too good to be true?

Well, now we have some compelling research data coming through for chaff lining and it seems you get really good value for money and it is true – chaff suppresses weed emergence.

In brief, this GRDC funded (US00084) research by members of the northern region weeds team, John Broster (Charles Sturt University, Wagga Wagga), Michael Walsh and Annie Rayner (University of Sydney, Narrabri) and Annie Ruttledge (Department of Agriculture and Fisheries, Toowoomba, Queensland) showed that:

  • As chaff levels increase, the emergence of weeds from under the chaff decreases;
  • Small-seeded broadleaf weeds (eg. sowthistle) are more easily suppressed than annual ryegrass; and
  • Chaff type can influence weed emergence, depending on the chaff proportion of the crop.

Learn more here.

Alphabet cross-resistance in South Australia

Do you want the bad news, the really bad news, or the really really bad news?

I’ll ease you into it.

The bad news:  A population of ryegrass from the Eyre Peninsula, South Australia has been confirmed resistant to all of the pre-emergent herbicides – Avadex, Arcade, Trifluralin, Propyzamide and Sakura, as well as two lesser-known herbicides EPTC and Thiobencarb.

“Crikey, this is the bad news!  Surely it can’t get any worse”

The really bad news: it was sampled in 2014 just two years after the release of Sakura in Australia.  You guessed it, metabolic cross-resistance is at play.

“Okay, give it to me, nothing will surprise me now!”

The really really bad news: a random survey in the South East of South Australia found many more populations of ryegrass with multiple cross-resistance to a range of pre-emergent herbicides, and the perplexing thing is that there is no predictable cross-resistance pattern.

“I’m going to have a cup of tea, a Bex, and a good lie down!”

This is the research by the team of Chris Preston, Peter Boutsalis, David Brunton and Gurgeet Gill from the University of Adelaide with GRDC investment.

This is the worst herbicide resistance news that I have seen in my 25-year long career simply due to the fact that so many herbicides are failing simultaneously.

But all is not lost, and we need to be on the front foot to give ourselves the best chance of success.  If you suspect that you have had a pre-emergent herbicide failure this year due to resistance a first steps action plan could be:

  1. Stop seed set if you can;
  2. And adopt harvest weed seed control now;
  3. And test;
  4. And use the testing results to develop a mix and rotate strategy; and
  5. Commit to smashing the seed bank.

You need to do all five to give yourself the best chance of success.

If you’re in the fortunate situation where a range of pre-emergent herbicides are still working for you, this should sound as a warning of what is to come and you should aim to smash your ryegrass seed bank now with a diverse approach while you can. To get a better idea, check out the WeedSmart Big 6 here.

Read the article in full here.

LEFT to RIGHT: UNTREATED>SAKURA 118g/ha>Boxer Gold 2500ml/ha | Back row EP162 | Front Row: susceptible ryegrass
Sprayed 4 weeks ago.

‘Clear and present danger’ – glyphosate resistance in the North

Researchers and growers have long been anticipating glyphosate resistance in the Northern cropping region and now the preliminary results from the first herbicide resistance survey in the region are confirming the ‘clear and present danger’ facing the grains industry.

A ruling of ‘clear and present danger’ was originally used to restrict American’s First Amendment rights to freedom of speech, press or assembly, particularly during a war. The suggestion being that exercising this right, could, at certain times put other Americans, or the war effort, in danger.

DAF, Qld weeds researcher Dr Adam Jalaludin collecting seed samples from a sowthistle escape as part of the first northern region herbicide resistance survey.

In the case of glyphosate, the suggestion is that while growers have previously enjoyed the ‘freedom’ to use this herbicide as their go-to, highly effective tool for weed control, there is now strong evidence that they should look for ways to protect this mode of action and implement a variety of tools such as the double knock, rotating herbicides and seed bank management as a matter of urgency.

Read more about it here.