Take home messages

• South Australian growers are generally happy with their first experience growing genetically modified (GM) canola in 2021, with many advisors reporting they expect area planted will increase in 2022.

• Advisors described better than expected weed control (particularly annual ryegrass) in GM canola as the key benefit of growing the crop.

• Other reported benefits included high yielding alternative varieties with different blackleg resistance options, options to manage herbicide residues using varieties with stacked herbicide tolerance, the availability of the PodGuard® trait to manage harvest shattering, a smaller than expected price difference to non-GM canola, and good access to receival points.

Background

In 2021, South Australian growers had their first opportunity to produce GM canola. Bayer forecast that 11% of the 2021 South Australian canola crop was planted to GM varieties, compared to 37% in WA and 24% in Victoria. This article will explore the key learnings from the 2021 growing season, using trial data and advisor observations from both South Australia and interstate.

Advisor Feedback

In preparation for this presentation, we had discussions with a range of agronomists across South Australia about their experiences with GM canola in 2021. A summary of their responses follows:

• GM canola was targeted at paddocks with either high ryegrass populations and/or where ryegrass populations were resistant to clethodim herbicide.
• Weed control generally exceeded expectations, and increased confidence in growing canola as a ryegrass-reducing tool.
• Most growers applied two applications of glyphosate. Planned third applications to TruFlex® varieties proved difficult to fit into the 2021 growing season.
• Ancillary benefits of having access to different major blackleg genes in high yielding varieties and traits such as PodGuard® to reduce potential pre-harvest losses were highly valued by many advisors.
• Many advisors are planning to increase the area planted to GM varieties in 2022 and would like to increase use of varieties with stacked herbicide resistance to both glyphosate and imidazolinone chemistry.
• Price differences to non-GM canola and lack of suitable receival points did not appear to impede adoption.

Variety Selection

With the removal of the GM moratoria in South Australia, growers and advisors now have access to an additional 21 varieties to plant in 2022 compared to previous seasons. Beyond the ‘traditional’ Roundup Ready® varieties, current varieties now include TruFlex technology, providing an increased window for post-emergent herbicide application, varieties with stacked herbicide tolerance of triazine/glyphosate and imidazolinone/glyphosate herbicide technology, and varieties with tolerance to triazine and glufosinate and varieties with the PodGuard trait, that has the potential to reduce pre-harvest losses (Table 1).

Table 1: Agronomic and disease information for current glyphosate-tolerant canola varieties.

Harvest maturity key: 3 = early, 4 = early-mid and mid-early, 5 = mid, 6 = mid-late, winter = very late (information provided by seed companies). Technology key: GT = Glyphosate Tolerant, TF = TruFlex, RR = Roundup Ready, LL = Liberty Link® (glufosinate tolerant), * = Provisional rating. Blackleg resistance rating key: R = resistant, MR = moderately resistant, MS = moderately susceptible, S = susceptible, VS = very susceptible. Adapted from: Ware, A (2021) Canola: 2022 South Australian Crop Sowing Guide pp. 53.

The current range of GM varieties offers a spectrum of flowering and maturity times that suit most of the canola growing areas in South Australia.

Over the past 3—4 years, in some of South Australia’s most intensive canola growing regions, large areas have been planted to cultivars with Group B blackleg resistance. This has placed considerable pressure on the Group B blackleg group, with foliar fungicide applications needed to manage disease levels. Alternative major blackleg resistance genes in high yielding GM varieties have the potential to reduce this pressure and are seen as another consideration factor in variety choice.

High canola prices are driving large increases in the area planned to be planted to canola in 2022. This is putting considerable pressure on seed supply for 2022, with seed supply of many popular varieties sold out early.

PodGuard

Shattering tolerance is highly valued in many of South Australia’s canola growing areas, as they are frequently subject to strong wind events during crop maturity. Windrowing has offered a successful strategy to reduce pre-harvest losses but can be an expensive and time-consuming process at a busy time of the year.

Many canola breeding companies in Australia have selection processes where they select for lines with increased tolerance to shattering, but at the moment BASF is the only company utilising this trait in the form of PodGuard. This trait is currently available in some of their GM canola varieties.

Considerable research, funded by GRDC, in both NSW and WA has found that varieties with the PodGuard trait have superior shattering tolerance to other commercially available varieties (data displayed in Figure 1).

Figure 1. Harvested seed yield of four canola varieties near Esperance in 2015, at three harvest timings, with corresponding weather data (Source: M Seymour, DAFWA).

However, research conducted by NSW DPI as part of the GRDC-funded Optimised Canola Profitability Project found that delaying harvest too long beyond maturity will result in losses of grain size (and yield), meaning that timely harvest of canola is still important even when shattering risk is reduced.

Herbicides and weed control

To adhere to Bayer’s licence stewardship agreement, growers must only use registered formulations of glyphosate at rates and crop growth stage timings that meet label requirements.

To maximise weed control in GM canola, the use of herbicides with other modes of action, beyond just glyphosate, is an important strategy to reduce pressure on glyphosate and ensure escapes of weeds such as annual ryegrass (ARG) are minimised.

This can be done through the use of pre-emergent herbicides and through the use of post-emergent mixtures.

Experience in 2021 demonstrated the importance of these strategies. Wind events during the 2020 harvest, resulted in considerable quantities of grain being shaken onto the ground and still being present at seeding in 2021. The break of the season was patchy in some parts of the state, leading to staggered canola and annual ryegrass germinations. This resulted in considerable cereal emerging with canola and ARG over a three—four week period.

Application of effective pre-emergent herbicides were able to reduce pressure on post-emergent applications.

The incorporation of tank mixes to GM canola at the 2-4 leaf timing, such as clethodim (Group 1) also provided effective control of ARG weeds and included an additional mode of action into the spray program, reducing the potential for development of metabolic resistance to glyphosate (Group 9) herbicides. Previous research conducted has also shown that many populations of ryegrass can have resistance to either clethodim, glyphosate or both herbicides (Boutsalis et al. 2021). Pot studies conducted showed that tank mixes of 1.15L/ha of Roundup Ready® PL and 500mL/ha Clethodim 240 displayed effective control across most populations tested, with control of ARG averaging 95% compared to 73% for standalone glyphosate and 79% for standalone clethodim (Boutsalis et al. 2021).

The wider application window that is possible with TruFlex varieties also proved valuable in 2021; where staggered germination had some plants larger than the 6-leaf at the planned 2nd application timing, exacerbated by high wind and rainfall events (and hence spraying opportunities) during June/July.

Conclusion

Growing GM canola varieties does provide benefits beyond the traditional herbicide tolerance traits that South Australian growers have accessed previously. However, to make the production of GM canola stack up financially against the other herbicide tolerance trait varieties, growers will need to capitalise on the benefits to account for reduced grain prices and technology fees.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support. GRDC funded NVT data will be discussed as part of the presentation, long term yield data from the 2021 growing season wasn’t available at the time of writing. The feedback from many South Australian advisors of their observations on GM canola production in 2021 was critical to the writing of this article. The SAGIT funded project: “Variety selection and weed management options for genetically modified canola”, will be further discussed as part of the presentation. Thanks to Mark Seymour for providing the harvest loss data from the trial at Esperance. The trial at Esperance was completed as part of GRDC DAW00227. BASF have provided internal data on the PodGuard® trait. Bayer CropScience provided local trial observations and National canola statistics.

References

Boutsalis P, Kleeman S, Preston C (2021) Canola technologies and herbicide resistance. 2021 Hart Field Day Guide, 62-65.

The National Variety Trials program

Introducing TruFlex canola

Contact details

Andrew Ware
EP Ag Research
7 Seaton Ave., Port Lincoln SA 5606
0427 884 272
andrew@epagresearch.com.au
@Ware_AH

Rebekah Allen
Hart Field-Site Group
155 Main North Rd., Clare SA 5453
0428 782 470
rebekah@hartfieldsite.org.au