Australia - Fighting feathertop Rhodes grass with new GRDC videos
Australia
December 14, 2017
The onset of the summer storm season could deliver more than grain growers are expecting – not just in the rain gauges but also in the paddock with falls likely to spark a fresh flush of problem weeds like feathertop Rhodes grass (FTR).
For some cropping regions of New South Wales and Queensland, this follows a dry winter and wet spring which is likely to have prompted germinations.
Research has shown FTR is often one of the first weeds to establish on bare ground and can germinate on as little as 10mm with emergence as soon as two days later.
FTR (Chloris virgata) is a major weed of fallows and roadsides in central Queensland and is becoming increasingly common in southern Queensland, NSW, Victoria and South Australia.
Control is becoming more challenging with confirmed cases of glyphosate resistant populations, forcing growers to rely on an integrated management strategy incorporating practices such as tillage, crop choice, crop competition, residual herbicides and the use of double knock applications in fallow.
However growers’ first line of defence comes in understanding the characteristics and behaviour of FTR, enabling an appropriate and effective integrated management strategy to be developed according to Independent Consultants Australia Network (ICAN) senior consultant Mark Congreve.
Mr Congreve explains the key factors of FTR, considerations when developing a control strategy, fallow herbicide options and fallow application recommendations in a new series of Grains Research and Development Corporation (GRDC) Know More videos. Videos are available on the GRDC’s YouTube channel www.YouTube.com/theGRDC or by following this link.
“The key thing is to start with the biology of the species and what we know about FTR. It’s going to be one of the first weeds to establish on bare ground, it likes germinating off the soil surface and, in favourable conditions and especially in wet summers where adequate control may be difficult to achieve, plants will rapidly produce large volumes of seed, with paddocks potentially becoming overrun very quickly,” Mr Congreve said.
“Understanding the biology of FTR, enables us to target its key weaknesses. These include its dislike of competition and the fact that the seed doesn’t last very long on the soil surface or even when it is buried. The seed will generally only last 12-18 months before either germinating or losing viability.
“If growers can prevent new seed from being set for one to two seasons, the seedbank will rapidly drop to very low levels. By stopping seed set, FTR can be virtually eliminated from paddocks within just a few years.”
When developing a herbicide control program for FTR in fallow, Mr Congreve encouraged growers to consider a range of herbicide options, and not rely on glyphosate.
“Extensive trial work has proven that glyphosate is relatively ineffective on FTR. FTR was never an easy weed to control with glyphosate, and now, populations of glyphosate-resistant FTR are present right across the northern region from central Queensland to southern NSW. As a result, growers can virtually forget about using glyphosate as a standalone control tactic,” he said.
“Other knockdown options for controlling FTR in fallow are limited, but some of the Group A herbicides such as Shogun® or haloxyfop have shown to be effective.”
However Mr Congreve cautioned against over-reliance on Group A herbicides, warning that they are among some of the quickest modes of action to select for resistance. There has typically been a higher frequency of individuals with genes that give resistance to Group A herbicides in the unselected natural populations of several weed species.
“Weed growth stage is critical to the performance of Group A herbicides with small, actively growing weeds more likely to be effectively controlled than larger or stressed weeds,” Mr Congreve said.
“All applications of Group A herbicides made in fallow should be followed by a double knock of a robust label rate of paraquat.
“This is both to help ensure effective control, but also to slow the selection for Group A resistance.”
Growers considering using Group A herbicides on FTR are urged to check the APVMA website https://portal.apvma.gov.au/pubcris to ensure that their product of choice is registered for use on FTR or a permit is in place to support use.
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