I’m off a family farm in South West Victoria; it’s a mixed farming enterprise comprising of cropping (mixed cereal and pulses), fine wool and prime lambs. I undertook my undergraduate degree at the University of Tasmania in Hobart on a full scholarship, it was a fantastic opportunity to be exposure to such diverse agricultural production; and during my honours year I investigated the impact of herbicide residues in poppies. My passion for research into herbicide resistance continued to grow and after finishing university I started a job with SARDI working in cereal, pulse and canola herbicide tolerance. I am currently undertaking a PhD and my research is aimed at providing a better understanding of resistance development in L. rigidum to pre-emergent herbicides in the Group J (thiocarbamates) family. This also includes management strategies for grower implementation. I was fortunate to make the discovery and publish a scientific paper ‘Resistance to multiple PRE herbicides in a field-evolved rigid ryegrass (Lolium rigidum) population’. Being supervised by three highly respected experts in this field Chris Preston, Gerjeet Gill and Peter Boutsalis at the University of Adelaide’s Weed Science Research Group, has been an incredible experience and privilege.
In laymen's terms, what did your research find?
A population of ryegrass from a paddock on the Eyre Peninsula, South Australia is confirmed resistant to all of the pre-emergent herbicides, Avadex, Arcade, Trifluralin, Propyzamide, Sakura, EPTC and Thiobencarb. This study documented the first case of field-evolved resistance to thiocarbamate herbicides in ryegrass.
In non laymen's terms: A population of rigid ryegrass (Lolium rigidum Gaudin) from a field on the Eyre Peninsula, South Australia, was suspected of resistance to thiocarbamate herbicides. Dose–response studies were conducted on this population (EP162) and two susceptible populations (SLR4 and VLR1). The resistant population exhibited cross-resistance to triallate, prosulfocarb, EPTC, and thiobencarb with higher LD50 to triallate (14.9-fold), prosulfocarb (9.4-fold), EPTC (9.7-fold), and thiobencarb (13.6-fold) compared with the susceptible populations SLR4 and VLR1. The resistant population also displayed resistance to trifluralin, pyroxasulfone, and propyzamide. The LD50 of the resistant population was higher for trifluralin (13.8-fold), pyroxasulfone (8.1-fold), and propyzamide (2.7-fold) compared with the susceptible populations. This study documents the first case of field-evolved resistance to thiocarbamate herbicides in L. rigidum.
Associate Professor Chris Preston, Geoff Philips, Dr Nick Berry, Associate Professor Gurjeet Gill, PhD Candidate David Brunton, Graduate engineer Keagan Grant
What is the problem with the herbicides, why are weeds becoming resistant so quickly?
We’ve spent the past 20-30 years using herbicides to control weeds and it's going to take considerably longer to undo. We know ryegrass is exceptional at evolving resistance to herbicides, but to do it in such a short space of time - wow. We have selected through herbicides, weed species that have the capacity to survive these applications. Widespread resistance to post-emergent group A and B and pre-emergents herbicides such as trifluralin is well known due to repeat use over many years. However, of greatest concern is resistance evolution to newer chemistries such as Boxer Gold, Arcade and more recently Sakura. Adoption of non-herbicidal weed control strategies remains low. Herbicides still remain the most cost effective weed control method and as a result resistance continues to evolve.
What is driving the rise in Herbicide Resistance we’re seeing?
History of herbicide use plays a major role but a reluctance by industry to readily adopt non-herbicidal weed control tactics has been a major driver of resistance evolution. Currently it seems when one herbicide fails, we go to the next and new herbicide modes of action are becoming less common. We’re not the only ones to have found herbicide resistance, in northern NSW and Queensland there have been new cases of glyphosate resistance in sowthistle, fleabane, feathertop rhodes grass and ryegrass; it seems to be a daily occurrence now. Getting industry excited about new methods of weed control is important. It will be necessary to incorporate non-herbicidal methods in combination with herbicides. Doing so will aid in prolonging the use of this precious resource.
What does your research mean for Australian Farmers in practical terms?
Herbicide resistance is a major threat to cropping systems worldwide. Many herbicides previously used for weed control, have failed or are failing to provide adequate control of major grass and broadleaf weeds. Annual ryegrass is one of these problematic weed species, which has developed resistance to a number of pre and post-emergent herbicides, across multiple herbicide groups (modes of action). The current story of herbicide rotation has clearly been demonstrated as a non-sustainable long-term tactic. Incorporating non-herbicidal methods of weed control in combination with strategic herbicide use is fundamentally the way forward.
How important is harvester setup for HWSC?
Harvester setup is the biggest thing to get your head around. If you can comfortably harvest with 2 headers, you may need to consider 3 if you want to do HWSC properly. We slow right down, for example, in bulky crops to allow the straw to process and in some conditions, you just have to stop and move to a different paddock. We are introducing windrowing this harvest to try and get the weeds while they are green before they've set, to reduce the losses at the cutter bar.
You've decided to upgrade your MY17 Seed Terminator, what influenced this decision?
We would've held off on the upgrade kit if it wasn't for the wear package released with the MY18 Seed Terminator. We're hoping to have fewer constraints from weed pressure, free up our rotations and increase profit margins.
What do you see as the future of this technology?
New chemicals aren't being developed, just different modes of action and we are running out of options pretty quickly. Harvest to harvest, all year round we have to be conscious of weed management; combining chemicals just isn't enough, weeds are developing herbicide resistance quickly. If they ban glyphosate, and one day it may happen, I estimate 60% of farmers within our local shire wouldn't be able to crop. We've all been looking for something mechanical for a long time. I think the mill technology needs to be introduced to all headers, across all farms, its a good move for Australian Agriculture.
For our dual enterprise that extra month of feed is worthwhile, but we might do better crops with the residue retention. If we ran a Seed Terminator it would certainly be harder with the livestock side of things unless of course Kikuyu and all those other summer feeds kick in. If we were 100% crop we would certainly have a Seed Terminator, but with the integration and the synergies of our dual enterprises a chaff cart is a better fit.
Has the chaff cart improved the weed burden in the three years you've been using it?
I can see areas that have been bad, that are now ok, but if we have a non competition year from getting too wet and the crop fails, then the weeds tend to build up quickly. Its up to us to perhaps spray top them in that situation to die it down. but when your collecting the weeds, then killing the weed seed with the sheep and then having a competitive crop its been working really well. I don't think we'd be able to do continuous crop like we've done for 22 years without it. We've only burnt a some paddocks couple of years in that time. Returning residues to the ground is really good, avoiding burning and keeping our reliance off the chemicals.
What crop rotations have you used in the past? How important is the combination of crop rotation, chemicals and HWSC?
In the early days we rotated lupins, wheat and canola. Lupins were ok where they grew really well, but you'd have anywhere from 10% to 50% of the paddock not survive the winter, so all of a sudden every time you grew lupins you would more than quadruple your weeds, especially rye grass. After that we tried rotating just canola and wheat following the dollars, we wanted a legume but didn't know of any that would work well in our environment, other than pasture, but then a couple of growers on the Island brought in broad beans which worked really well. Broad beans built up our rotation and compete fairly well with the weeds. Having three reasonably competitive crops, in addition to the chemical regime, and the collection of seeds with the chaff cart, we feel we can keep going and not have to give up on farming.
Nick Berry (left) with his mum and dad Lloyd & Christine Berry on the family farm.
How does it feel not burning and what did you do instead of burning this year?
Burning an entire program of either windrows or chaff dumps was quite a time consuming job when you consider the time involved in the whole process from installing firebreaks around chaff dumps to lighting and monitoring fires and weather conditions. One of the things I enjoyed this year was not having to constantly monitor the wind forecast looking for good opportunities for burning dumps and then having to adjust the other farm activities to fit around this. This year we spent more time on doing some more liming, equipment prep for seeding. It certainly felt like we had more time. I think this is a difficult thing to put a value on but I believe that when I have seen it estimated at $2/ha it is undervalued…..obviously depending on what you choose to do with that time
What do you think not burning does for your soils and future productivity?
I think maintaining soil cover is important. Spreading the residue evenly across the width of the harvester is still a challenge though. We may see some N tie up from the build up of cereal stubbles in particular but I think the return of K into the system along with some moisture retention improvements should go a long way, if not beyond offsetting this.