STEWARDSHIP FOR ROUNDUP READY? CANOLA - A FOCUS ON THE COMPONENTS THAT REDUCE POTENTIAL SELECTION PRESSURE FOR RESISTANCE TO GLYPHOSATE

| Date: 16 Sep 2009

Figure 1. PRAMOG Summary Sheet.

Roundup Ready® canola provides growers with a new option as part of an overall weed and herbicide management strategy in their cropping rotation. It gives growers the alternate option of using Roundup Ready Herbicide, Group M, over the top of their canola crop. The application of Roundup herbicide provides farmers improved flexibility in timing of application for weed control and the range and size of weeds that can be controlled in one application, when compared to current weed control options in conventional or Triazine Tolerant canola.

As part of the introduction of Roundup Ready canola, Monsanto Australia has developed a Resistance Management Plan (RMP) in conjunction with leading Australian weed scientists to ensure the sustainability of both Roundup Herbicide and the Roundup Ready canola technology. Weed resistance to glyphosate, the active ingredient of Roundup Herbicide is rare, but does exist in a number of Annual ryegrass (Lolium rigidum), Barnyard grass (Echinochloa colona) and Liverseed grass (Urochloa panicoides) populations in Australia.

Annual ryegrass in particular is a significant weed of concern in Australian broadacre farming systems. Populations of annual ryegrass resistant to various herbicide groups have developed throughout South-Eastern and Western Australia.

Potentially the simplest mechanism for reducing the potential for resistance development is to not use glyphosate in the year following Roundup Ready canola. However, this approach is not always practical, in which case farmers will require more flexible options.

The Roundup Ready canola Resistance Management Plan incorporating the Paddock Risk Assessment and Management Option Guide (PRAMOG®) allows farmers to make informed decisions on how to manage Roundup Herbicide sustainably (within Roundup Ready canola) on a paddock by paddock basis. PRAMOG is a compulsory component of growing Roundup Ready canola and the results must be recorded before a grower can be granted a Technology User Agreement (TUA) to buy and grow Roundup Ready canola.

The Resistance Management Plan for Roundup Ready canola utilizes PRAMOG (Figure 1) as a step-by-step risk assessment process on a paddock by paddock basis - the three steps are:

Step 1: An evaluation of glyphosate use history in the paddock – this step involves looking at the past 20 years of glyphosate use on a paddock in terms of the number of times glyphosate has been used and the selection pressure that individual applications would have for resistance development. For example a winter fallow application of glyphosate will impose more selection pressure than a knockdown followed by full soil disturbance so it is given a higher rating.

Step 2: A determination of glyphosate resistance “risk status” for annual ryegrass – by combining the history of glyphosate use from step 1 with the number of other modes of action that a farm has resistance too, this step indicates which of the 3 different categories for management in the year following Roundup Ready canola the paddock falls into. The three categories are:

1. A minimum of one additional management practice must be nominated and implemented.
2. A minimum of two additional management practices must be nominated and implemented.

NG - A minimum of two additional management practices must be nominated and implemented and Monsanto recommends that you do not use glyphosate in the year following Roundup Ready canola.

Step 3: A choice of management actions based on “risk status”. Depending on your resistance risk from step 2 you choose 1 or 2 additional management practices for the year following Roundup Ready canola. A number of options for these additional practices along with an indicative level of control are included in the Resistance Management Plan.

Figure 1. PRAMOG Summary Sheet.

In the 2008 limited commercial release of Roundup Ready canola in Victoria and NSW around 30% of paddocks were in the PRAMOG 1 category, 60% in 2 and 10% in NG (figure 2). This number varied by region with some areas having significantly more NG paddocks than others. The higher ratings were generally due to farmers operating minimum till farming systems with a high reliance in glyphosate. However, in these systems farmers are generally practising other integrated weed management (IWM) techniques and for the 2009 canola season there has been a change in the rating of some glyphosate applications when people practice IWM to reflect the effect that this has on resistance development.

Figure 2. 2008 Roundup Ready paddocks by PRAMOG category (n=160)
Figure 2. 2008 Roundup Ready paddocks by PRAMOG category (n=160)

In 2008 all 160 paddocks were inspected 14 -21 days after Roundup Ready Herbicide application by the Technology Service Provider to assess the performance of the herbicide application. Approximately 70% of paddocks rated their weed control rate as Excellent and 30% as Good. No paddocks were rated as Average and only 1 Poor level of weed control was recorded. There was no difference in the rating of the effectiveness of the weed control between the different PRAMOG groups (Figure 3).

Figure 3. 2008 Weed control rating by PRAMOG category.
Figure 3. 2008 Weed control rating by PRAMOG category.

Through the Resistance Management Plan, Monsanto is working to ensure the sustainability of Roundup Herbicide in the Australian agricultural sector. In addition, a major benefit of Roundup Ready canola is that Roundup Herbicide can control weeds with established resistance to other groups of herbicides, for example Group A or Group B resistant weeds. Controlling these weeds in the canola rotation stops weeds from setting seed, which reduces recruitment to the weed seed bank, and controls weed proliferation in following crops in the rotation. The availability of Roundup Ready therefore supports the sustainable use of Triazine Tolerant and IMI herbicide systems in crops such as lupins and other pulse crops, as well as canola.

The Roundup Ready canola accreditation program also forms part of the stewardship of this technology. All growers intending to grow Roundup Ready canola are required to complete an accreditation program that includes information focused on the adoption and implementation of the Resistance Management Plan. Growers are also provided with a detailed technical manual, which acts as a reference document for the technology, and for the accreditation course. The document covers, in detail, all elements of the Crop Management and Resistance Management Plans for the technology, as well as agronomic guidance and other relevant information.

Contact details

Dr James Neilsen
Monsanto Australia
Level 12 600 St Kilda road
Melbourne 8008
Ph: 03 9522 7122
Fx: 03 9522 6111
Email: james.eric.neilsen@monsanto.com