Mix and match to avoid herbicide resistance

Herbicide resistance is a challenge no farm advisor or grower can afford to ignore. Its cost has been well documented around the world. Beyond lost yield, resistance reduces rotational choice, farm income and asset values.

Since 1979 in New Zealand, 20 different weed species have developed resistance to herbicides from one or more mode-of-action groups. The list includes glyphosate, perhaps our most commonly used herbicide. While that’s an alarming trend, on a global scale the number is low – by comparison the United States has 161, Australia 91 and in Britain, 27. That contrast highlights that it is not too late for us to modify our weed management practices, by ensuring essential herbicides such as glyphosate remain effective for longer. How do we achieve this? Well, we simply mix it up! We need to ensure our weed control strategies are diverse and incorporate non-chemical as well as chemical control tools without reliance on any single solution.

NON-CHEMICAL

One example of non-chemical weed control is crop rotation, which broadens your herbicide control options. Other non-chemical measures you can use to reduce the impact of weeds include increasing your seeding rates to increase crop competition, especially with cereals; not overgrazing to ensure you maintain highly productive and competitive pastures; spray-topping to reduce weed seed-set in pastures the year before cropping; and cultivation to deeply bury weed seeds before planting.

CHEMICAL

It is important to use herbicides at full label rates and ensure you rotate between different mode-of-action groups and not just herbicide brand names. New Zealand has 88 glyphosate brands registered to 25 registrants and they all have exactly the same mode of action – Group G. Always target young, actively growing weeds to improve control and reduce weed escapes. Make sure the correct adjuvants are used. When applying a knockdown herbicide, always look to reduce weed resistance selection pressure by tank-mixing it with another herbicide. The ideal partner is one that not only represents a different mode of action but is also effective in its own right against the target weeds. A great example of a strategic tankmix partner for glyphosate in the pre-sowing knockdown window is Sharpen®. It is a fast-acting, broadspectrum herbicide that increases the speed and spectrum of weed control compared with glyphosate on its own. Even better, as the only systemic herbicide in Group E (which includes carfentrazone), Sharpen allows far less regrowth across more weed species than alternative tank-mix partners. While the development of resistance can’t be totally prevented or reversed, it can be forestalled and its impact managed if we all take action now and incorporate the “mix it up” approach into our weed control strategies.

| Weed control strategies should incorporate non-chemical as well as chemical control tools.

For more information, contact your Farmlands Technical Field Officer, or the friendly team at your local Farmlands store.

Article supplied by BASF New Zealand

Grow fruit, not weeds

Control weeds for the whole growing season with Chateau® residual herbicide. Team up with Amigo® adjuvant to increase droplet retention and assist with drift control. • Ideal for kiwifruit, pipfruit and stonefruit as well as grapes • Controls weeds for 4 to 6 months • Pre-packed in water soluble bags – no weighing or handling required • Successfully trialled throughout NZ • No residues occur in fruit or vine foliage when used as directed Contact your local Farmlands Technical Advisor or visit nufarm.co.nz