THE WEED Smart team has come up with six key areas that farmers can think of when making their agronomic choices that can help reduce the risk of herbicide resistant weeds.
Speaking at Weed Smart Week in Horsham, Victoria, last month Weed Smart western extension agronomist Peter Newman said there were some easy steps that could help prolong the efficacy of key herbicides and help reduce the weed burden.
Firstly he said a diverse rotation including crops and pastures to allow a similarly diverse range of herbicide products to be used was a good tool.
"Using rotations including a double break crop, fallow or even pasture can be great in running that weed seed bank down."
He said not placing too much emphasis on any one herbicide was also important.
"Rotating herbicides buys you time, mixing herbicides buys you extra shots, you can also ensure the risk of resistance is lower by always using full rates."
Another herbicide-related tip was to use a double knock strategy, with a particular view towards reducing the risk of glyphosate resistance.
"Following glyphosate with a high rate of paraquat controls the survivors of the glyphosate application."
Mr Newman said crop competition was another good way of running down weed numbers.
"Use narrower row spacings and higher seeding rates on east-west sowing and the crop will be better able to compete against the weed species."
He said stopping weed seed set was critical.
"It really is a case of take no prisoners, so options such as crop topping, hay and brown manure are all really good in terms of stopping the weeds setting seed."
Finally he said harvest weed seed control had grown in importance in terms of overall weed management strategies.
"It is the holy grail when you can capture weed seed survivors at harvest."
Mr Newman's colleague, southern region extension agronomist Greg Condon said there were ways of 'stacking' the Big Six to improve further on weed seed removal, such as harvesting high and leaving high amounts of crop residue.
"When you harvest higher there is more shade and it can store more moisture."
"Sowing on narrow rows is also good in terms of getting that competition.
He also recommended using rotations as a means to target problem weeds.
"In your faba bean or canola phase you can really hit the grass weeds hard if that is what you have a problem with."
Mr Condon also advised that early sowing was effective in lessening the weed burden, however he cautioned that it was not always possible due to the timing of the opening rains.
He said harvest management, such as spreading the residue evenly was a good way to ensure there was no problem at sowing.
"Sowing really begins at harvest now," he said.
"You have to be careful, for instance canola just doesn't like cereal straw, there are problems with hair pinning."