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Helping herbicides through harvest weed seed control



A ‘Story from the Field’ about a plant biology professor? Sounds a bit inappropriate, but then again, Steve Powles is no ordinary academic. He’s been involved in farming all his life and was one of the first to identify resistant ryegrass back in the 1980s. As the owner of a 300 ha farm devoted to wheat and canola cropping in Western Australia, he’s also fully aware of how severe a problem ryegrass and wild radish is for Australian grain farmers – and knows from personal experience how to manage it.

For six generations since the 1820s, the Theron family has been farming in the Swartland region of the Western Cape. Andries (56) and his son Frikkie (30) co-manage the 1,000-hectare Soutkloof Farm near the small town of Moorreesburg 90 km north of Cape Town. In this region wheat has always been the main crop, but it’s not just drought that has become a growing threat over the past 20 years. Up to the mid-1990s, Swartland farmers grew more or less nothing but wheat on fertile soils with high yields. But when herbicide resistance first raised its ugly head back then, Andries started rotating. “You’ve got no chance to exclude yourself from your neighbors. Herbicide-resistant seed spreads fast and no farm is an island,” Andries points out.


Crop rotation critical

“Until the mid-1990s I just grew wheat, but then I noticed that yields were dropping and I’ve since been experimenting with other crops – first canola and now barley as well,” Andries explains. Right now, half the Soutkloof acreage is fallow land (medics, clover, etc.) or cattle pasture, and half arable land. “Crop rotation is critical in controlling weeds. Our canola is ok because each year we can still use a different mode of action to tackle broadleaf weeds. On ryegrass we take a zero tolerance line with a pre-emergence spray. It’s the last effective mode of action we’ve got so we’re protecting it carefully. During the growing season we’ve got no other crop protection agent we can use to take out weeds. What really worries me is wild radish, which is becoming more and more resistant. In badly infested areas we plow it under, although we know that feeds the weed seedbank, or pull it out manually.” What’s more, the drought conditions of recent years are badly affecting spraying applications. “Right now, they’d only be about 60% effective if we didn’t increase the amount of water in the crop sprayer to maximize efficiency. We’re using 150-200 liters of water per hectare instead of 100,” Andries adds. With water a scarce resource in the Western Cape that adds to the problem. But based on his decades of experience and expertise in grain farming Andries has developed an integrated approach to tackling these issues.


Farmer-funded research

Andries’ concern for the wellbeing of his fellow farmers, particularly in the context of increasing weed resistance, has been the driving force behind his engagement in various agricultural associations as Chairman of the Winter Grain Trust, member of the Executive Committee and recently retired Vice-Chairman of Grain SA (which provides strategic support and services to South African grain producers to support sustainability), and Vice-Chairman of the Protein Research Foundation. “Farmers here in South Africa are used to taking on responsibility,” Andries explains, “and all the research on weed resistance, for example, is funded by us farmers!” He firmly believes that weed resistance is an issue that can only be tackled by integrated efforts from the entire agricultural community and crop protection industry.


“No silver bullet”

Andries explains the economic problems of wheat production, not just in South Africa. With profits low, farmers need to save money (e.g. on herbicides). Besides, many of them do not realize just how severe the weed-resistance threat is and are still expecting new modes of action to turn up. “But there is no silver bullet,” he says. The only way to control weeds is through diversity in the methods used. “It’s so important to educate farmers about these issues,” he adds. “And I’d also like to see higher-quality advice from agricultural advisors here in South Africa. In Australia, for example, their recommendations are much better.”

Andries’ son Frikkie had the chance to go and farm in Canada. It was a tempting prospect but he decided to become the seventh-generation Theron to run Soutkloof Farm. “He wanted to try and make a difference here,” Andries says with pride. The Therons can’t do a rain dance to beat the drought, but they are doing a lot to tackle resistant weeds – and spreading the message throughout South Africa.

Non-chemical help for herbicides

In Australia there is high awareness of weed resistance because it is a massive issue for grain farmers. “In countries where there’s less awareness, it’s mainly because weed resistance isn’t impacting farmers enough. But it will,” Steve says. “Our failure to get the message across to farmers is what has disappointed me most in my career. That’s why we now spend 30% of our research budget on communication measures.” Steve is under no illusions about how severe the resistance problem is worldwide: “The golden age of herbicides is over. Back in the 1980s, new herbicides were common and resistant weeds rare. Nowadays, new herbicides are rare and resistance weeds common. The low-hanging fruit has been picked. The chemicals we still have are precious and need to be protected. That’s where I see a vital role for harvest weed seed control – in helping herbicides.”