9 August 2012
Food production is one of the greatest global challenges of the 21st century, and in order to sustain world food production and Australia’s long-term role as an important part of the region’s food bowl, Australian growers need reliable control of crop weeds.
Herbicides are an essential management tool for controlling yield-reducing crop weeds, yet their sustainability is threatened by the growing evolution of herbicide resistant weed populations.
“The average consumer doesn’t think about weeds when they are buying their bread, rice, milk or meat. However, throughout Australia, herbicide resistance in weeds is having a dramatic effect on yield production,” said Sue Cross, Head of Development at Bayer CropScience.
Chris Preston, Associate Professor at the School of Agriculture, Food and Wine at the University of Adelaide said, “The financial effect of resistant weeds on yield varies depending on the crop and the weed, and could cause limited to total crop loss”.
Strategic approach needed
“Tackling the issue of herbicide resistant weeds should not rely solely on finding new herbicide solutions,” Sue said.
“The cost of discovering and developing new chemicals is increasing and the regulatory hurdles are extremely high, which means we should protect what chemistry we already have.
“The best way to do this is by following an integrated approach to weed management, utilizing also the many non-chemical tools available.
“The need for a strategic approach is highlighted by the plight Australian grain growers’ face in the battle against resistant weeds, particularly annual ryegrass,” Sue noted.
Chris Preston said annual ryegrass has the right biology to enable it to develop herbicide resistance.
“Ryegrass is a challenge for growers because it has great genetic diversity, produces large numbers of seed and is cross-pollinated by wind; but its seed does not have a long life in the soil.
“In Australia we built up large ryegrass populations as pasture for sheep, but as the wool industry became less attractive, we converted much of the land to crops, tackling the ryegrass solely with herbicides, but farmers need something more sustainable,” Chris said.
In the face of growing environmental and economic pressure, sustainable farming is becoming accepted as critical to maintaining the viability of individual farms and the industry – locally and globally.
“Bayer acknowledges weed resistance and the challenges it presents. Our focus has been on the grower and providing solutions, not just purely product-only answers,” Sue said.
Integrated Weed Management: Strategic response
Integrated Weed Management (IWM) is a strategic response compatible with sustainable farming. It involves long-term management of weeds by combining targeted chemical, biological and cultural methods.
“IWM is compatible with conservation farming as it provides a sustainable broad-based way to manage weeds long term,” Sue said.
“Bayer is a vocal advocate for IWM and our approach includes our products, Sakura® and Velocity®, which are complementary to IWM programs.
“We work closely with growers and advisors to help them develop and implement practical IWM strategies so their farms can be more efficient and more sustainable year on year. This means more profits from healthier crops and better yields,” Sue added.
Mike Rouch, Senior Development Specialist from Bayer, said Bayer’s products fit in well with IWM systems.
“Sakura for example is a pre-emergent herbicide, and when incorporated with other weed management practices, it can help slow the buildup of resistant weed populations where they are not already established,” Mike said.
Based on the active ingredient pyroxasulfone, Sakura has demonstrated up to 97 per cent control of populations of annual ryegrass resistant to Group A, B and D herbicides. The product has an excellent fit with conservation farming as it works particularly well with a minimum or no-till farming approach where it facilitates the use of knife points to plant seed with little soil disturbance.
“An added benefit of Sakura is that it is effective in up to 50 per cent trash cover.”
Rick Horbury, Technical Advisor from Bayer, said Velocity is a post-emergent herbicide that should also help extend the life of existing and important herbicide options such as Tigrex®, Ally® and MCPA LVE.
“Velocity contains a unique mode of action and introduces a Group C+H herbicide into the cereal herbicide rotation. This prolongs the useful life of existing chemistry which assists growers in maintaining a more viable gross margin in the long run,” Rick said.
IWM: Strategy plus tactical options
In addition to herbicide applications and rotating herbicide mode of action (MOA) groups, growers should consider crop rotation and phytosanitary measures such as equipment sanitation, managing weed seeds at harvest and altering soil cultivation practices as part of an overall weed management strategy.
Sue added, “The key to IWM is diversity of cultural and chemical management tools that effectively and sustainably reduce weed populations in subsequent crops.
“Many of the measures may individually have limited effect but, in combination with other practices, they can work together resulting in much greater overall effectiveness in controlling weeds,” Sue said.
Andrew Weidemann, Grains Group President of the Victorian Farmers Federation (VFF) has successfully used an IWM approach in his various grain crops on his farm in the Wimmera.
“Without an integrated approach to managing resistant weeds in my crops, we would experience much more crop loss year on year and a build up of herbicide resistant weeds,” Andrew said.
“In the integrated approach of managing herbicide groups of chemicals, we strategically rotate the use of chemical groups and implement a hay program across those areas that have a high potential for resistance,” he added.
IWM: Sustainable future
Looking to the future, Sue has noted that IWM studies have shown that the integrated approach provides sustainable weed control, and creates an environment for better weed management.
Another great benefit of IWM is that it gives farmers the flexibility to grow the crops that they want to grow on their farm.
"Integrated weed management is really the best path forward. We’re seeing more and more growers adopting the technique. With the right education and support, IWM programs such as Andrew’s are effective and easily incorporated into growers’ current and future farming practices.
“Our purpose is to propel the future of farming in Australia. This expresses Bayer’s ambition to address the big issues including the long-term sustainability and viability of Australian agriculture,” Sue said.