With warmer than average winter temperatures accelerating the growth of northern wheat crops, it is imperative that growers give top priority to weed control this season to maximise crop productivity and avoid the costly issue of herbicide resistance.
In many areas this will rely on the successful in-crop management of grassy weeds such as wild oats and annual ryegrass which already harbour widespread resistance to commonly used herbicides.
Herbicide resistance management is a key investment area for the Grains Research and Development Corporation (GRDC) which is funding numerous programs to tackle the problem including an integrated weed management research project as well as the WeedSmart initiative to promote the long term sustainability of herbicide use in Australian agriculture.
GRDC manager regional grower services - north, Sharon O’Keeffe said cereal growers needed to employ a variety of tactics to effectively combat weeds including an early spray program, robust spray rates and correct spray application with consideration given to timing, wind speed, water rate, applicable droplet size, boom height and travel speed.
“The quality of water used in tank mixes is also extremely important, particularly if there are high water rates, as poor quality water can adversely affect herbicide efficacy,” Ms O’Keeffe said.
“Adjuvants must be used correctly with full consideration given to compatibility with the target weed and herbicide, including any adjuvants included in other products in the tank mix.
“In high grass weed densities, growers need to be particularly careful that tank mixes aren’t going to antagonise or reduce the efficacy of any group A herbicides which already exhibit issues with weed resistance.”
In the case of wild oats, resistance was initially identified in Group A herbicides such as Topik® however populations are now becoming increasingly resistant to Group B herbicides like Atlantis® and Hussar® as well as Group Z herbicides such as Mataven®.
In cases where the resistance status of weeds have been confirmed or poor control with a Group A chemical has been experienced in the past, Ms O’Keeffe strongly recommends that growers take an integrated approach to weed control, rotating herbicide groups as well as utilising practices such as crop rotations and fallow management.
She said it was critical that growers assess the effectiveness of each herbicide application and act quickly to remove any surviving plants.
“Keep a close eye on treated paddocks and either mechanically remove survivor weeds or mark the patches of concern via GPS so that salvage control can be undertaken,” Ms O’Keeffe said.
“It’s important that growers consult with their agronomist on control strategies to determine the impact on both the crop and the farming system as a whole.
“Growers need to be proactive rather than reactive in their weed management strategies.”
Department of Agriculture, Fisheries and Forestry (DAFF) Principal Research Scientist Dr Michael Widderick said there was a perception among some growers that small outbreaks of resistant weeds were not economical to control.
However he said it was important to remember that some weeds can set between 50 and 1000 seeds annually and if not controlled, can take over paddocks in less than 10 years.
“An integrated weed management strategy is the most effective method of controlling problem weeds, and this can include harvest weed seed management, crop sequencing, strategic tillage, double-knock treatment of weeds (chemical or mechanical) and use of pre-emergent herbicides,” he said.
The WeedSmart Northern toolbox outlines handy resources for growers to help with the implementation of successful integrated weed management strategies.
For more information, visit www.weedsmart.org.au/wp-content/uploads/2013/01/WeedSmart_SustainabilityGuide_V14-Northern_LR.pdf (581KB PDF)
Caption: GRDC manager regional grower services – north Sharon O’Keeffe said growers needed to be proactive rather than reactive in their weed management strategies.
GRDC Manager Regional Grower Services, North
0409 279 328
Elise McKinna, DAFF Media & Communication Officer
07 3087 8576
Sarah Jeffrey, Senior Consultant Cox Inall Communications
GRDC Project Code
UQ00062; UA00124; GOA0002