Now, prior to harvest or cutting of crops is an opportune time for grain growers to collect weed seeds for herbicide resistance testing.
Determining the status of herbicide resistance provides growers with valuable information on the effectiveness of herbicides on target weeds.
Grains Research and Development Corporation Crop Protection Officer – South, Aaron Long said priority should be given to testing weeds in high risk paddocks where there is a lengthy history of herbicide use and herbicide survivors have been allowed to set seed.
He said it was important for growers to have a good grasp of the status of herbicide resistance within their own paddocks.
University of Adelaide and Plant Science Consulting herbicide resistance researcher Peter Boutsalis said while pre-harvest was the perfect time to collect samples of weed seeds for testing levels of resistance, collection could also occur during and after harvest or cutting crops for fodder.
He said contaminated grain or header screenings could also be sent for testing as commercial testing services can separate weed seeds from other material.
If the seeds are not completely dry, they should be sent in paper envelopes to avoid rotting in plastic packaging.
A paddock that contains more than one suspect area, samples from each area should be tested separately because resistance can vary across a paddock.
Testing three or four herbicides of differing modes of action can be helpful in identifying those herbicides that are still effective.
GRDC recently announced that resistance to pre-emergent herbicides from a total of three mode of action groups has now been confirmed in Australian annual ryegrass populations.
Weed seed resistance testing services are available via:
Peter Boutsalis, Plant Science Consulting, Adelaide (SA): 0400 664460, www.plantscienceconsulting.com.au
More information on herbicide resistance and weed management is available via the GRDC’s Integrated Weed Management hub at www.grdc.com.au/IWMhub