Ground Cover Supplement : GC Supplement - Weeds
5 Issue 128 | May – June 2017 | GRDC GROUNDCOVERTM SUPPLEMENT: WEEDS GROUNDCOVER NORTHERN REGION to 95 per cent if seeds are buried by cultivation to five centimetres. In addition, the seed appears short-lived, with burial for seven to 12 months reducing viability by greater than 90 per cent.” As concerns about herbicide resistance rise, the use of residual herbicides is increasing, but their efficacy can be limited when application is not followed by regular rain events. Performance can also vary by soil type and seedbank distribution. Mr Daniel also points out that residual herbicides will invariably lead to re-cropping restrictions. For this reason, the frontline weapon is still rotations. “Sorghum is considered the blowout crop for feathertop Rhodes grass, so if you’ve got a paddock with a real problem, put mungbeans in that paddock and sorghum into the others. It’s about tweaking your system rather than changing everything. “The key message is the need to put as much focus as we can on non-herbicide treatments.” ENGINEERING HOPES Narrabri-based University of Sydney researcher Dr Michael Walsh is running a project to evaluate engineering solutions to weed control. Under assessment are electrocution, heating, lasering and microwaving, and commercially available units such as harvest weed seed control systems. As research points more and more to site- specific weed control being the best option for growers, Dr Walsh says the feasibility of weed mapping is also being examined. Dr Walsh believes that more targeted weed-control technologies such as these could reduce the cost of weed control by as much as 80 per cent. “From an engineering perspective, it’s easy. The hard part is making the technology practical for on-far m use.” FENCELINE TREATMENTS NSW Department of Primary Industries technical specialist (weeds) Tony Cook is working on a project to develop new treatments for key weed species that often populate areas adjacent to crops such as fencelines and far m tracks (see breakout box). He says fenceline weed management has become crucial to the overall suppression of weed populations, but now needs a more comprehensive approach than simply relying on glyphosate. The project’s first experiments, on the Darling Downs and in northern and central NSW, suggest that bromacil can be mixed with other herbicides to broaden the spectrum of weed control to provide long-term control of broadleaf weeds and annual ryegrass. Mr Cook says more effective weed control could result in cleaner cropped By Tony Cook, Bill Davidson and Rebecca Miller Even with the best possible control of in-paddock weeds we are still prone to invasion from adjacent weed-infested, non- cropped areas such as fencelines, irrigation channels and farm tracks. The biggest threat from non-crop areas is the windblown weeds that can spread large distances. With respect to control, a new five- year project in the northern region has confirmed that bromacil can be mixed with other herbicides to broaden the range of weeds controlled in non-crop areas. Work in the southern region has already confirmed bromacil’s effectiveness at controlling ryegrass, but growers in the north are looking for options to control a much wider range of weed species. Fleabane, common sow thistle, windmill grass and feathertop Rhodes grass are widely distributed and of particular concern in the northern region. Annual ryegrass is more of a problem in central and southern NSW. In the past, growers have relied on glyphosate to control weeds in non-crop areas. But with glyphosate resistance now found in all of these weeds, it is clear that a major change of approach is required. SEARCH FOR NEW TREATMENTS This project aims to identify new treatment options with alternative modes of action. Attitudes about fenceline hygiene vary between regions. Clean fencelines in southern and western regions were driven by the need to have a good firebreak, with most farms already managing these non-cropped areas. However, in the north, fenceline management is a mixed picture. To improve this situation, it needs to be more widely understood that fenceline weed management can no longer be an ad hoc farm practice. It requires a dedicated application of treatments, either pre-emergence to weeds or at the early growth post-emergence stages. Finding suitable treatments for irrigation channels is a more difficult task. The list of ‘aquatic approved’ products from which to select is much more restrictive, but potential options are being evaluated. The key aim of this project is to collect data to support registration of new weed treatments with the Australian Pesticides and Veterinary Medicines Authority. Once registered, these options will be promoted to enable growers to better protect their crops from windblown weeds. GRDC Research Code US00084 More information: Tony Cook, 02 6763 1250, firstname.lastname@example.org paddocks and the elimination of the green bridge between crops, which has the potential to carry diseases and pests. o GRDC Research Codes NGA00003, US00084 More information: Richard Daniel, 0428 657 782, email@example.com; Dr Michael Walsh, 02 6799 2201, m.j.walsh@ sydney.edu.au; Tony Cook, 02 6763 1250, firstname.lastname@example.org PHOTO:TONYCOOK ATTENTION TURNS TO FENCELINE HYGIENE GROWER MESSAGE With glyphosate-resistant weeds on the increase, it is time to look for other options for controlling weeds in fencelines and other non-crop areas. Poorly managed fencelines are a refuge for an array of weeds that are likely to affect adjacent cropped paddocks.
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