You are here

Share page with AddThis

Old herbicide classification making way for the future

Vine Talk columnist and Syngenta Technical Services Lead Dr Brandy (Belinda) Rawnsley.
Have you heard the latest tips, tricks and industry advice? Vine Talk author, Dr Brandy (Belinda) Rawnsley takes a look at the issues facing grape growers.

Resistance management, be it related to fungicides, insecticides or herbicides, is critical to the long-term sustainability of our industry. Australia has been at the forefront of resistance management, being the first country to mandate Mode of Action classification labelling in 1992. Several revisions to this system have been required to reflect current knowledge, however this year sees a global alignment of the herbicide classification system.

From July 2021, you will see numbers to reflect the mode of action on all new herbicide labels and in communications. It is not a simple exchange of C=3 as an existing American system has been adopted, so the number system is not sequential. Thankfully, there will be a three-year transition period so we can all adjust our manner of thinking!

There are multiple reasons for this change: letters are self-limiting; alignment to other global systems; insecticides and fungicides are already using a number system.

There will be some realignment of individual active ingredients, again, to reflect better understanding of how the chemical behaves; however, most resistance management strategies will largely remain the same.

For viticulturalists, herbicide management will remain largely unchanged. SPRAY.SEED® (as well as GRAMOXONE® 360 PRO and REGLONE®), currently group L, will become group 22. FUSILADE FORTE®, currently group A, will become group 1. Similarly, many of the pre-emergent herbicides will have a simple exchange of letter to number.

Which brings us to a timely reminder to apply a pre-emergent herbicide. Determine your pre-emergent herbicide based on the weed spectrum anticipated, soil type and herbicide history. Depending on the product of choice, this is best applied post-defoliation or pre-budburst rather than waiting until spring. By that time, annual grasses will have germinated, making the problem considerably worse. If weeds are currently an issue, use a SPRAY.SEED knockdown first or with your residual pre-emergent. 

Getting a weed management plan in play now will save you time and money later.



Dr Brandy (Belinda) Rawnsley
Technical Services Lead - Horticulture & Viticulture
Syngenta Australia
[email protected]


About Syngenta Australia
Syngenta is a leading agriculture company helping to improve global food security by enabling millions of farmers to make better use of available resources. Through world class science and innovative crop solutions, our 28,000 people in over 90 countries are working to transform how crops are grown. We are committed to rescuing land from degradation, enhancing biodiversity and revitalizing rural communities. To learn more visit and