The old adage that ‘when you buy quality, it only hurts once’ rings true in the case of the new herbicide Sakura® (pyroxasulfone) to combat annual ryegrass.
Many cheap products can appear to be great value at first, but when they break down soon after purchase they are often deemed to have been a waste of money.
The same is true for herbicides.
When you buy seemingly expensive new herbicides and apply them at the full label rate, it hurts the hip pocket.
Cutting the rate saves money – making your budget look good - and appears to work well at first.
Until, a few years down the track, herbicide resistance emerges as a result of using below recommended label rates.
And, not only has the weed population on your farm developed resistance to this herbicide, it can also develop cross resistance to herbicides that you have not even used yet.
That is the alarming finding of GRDC-supported UWA-based Australian Herbicide Resistance Initiative (AHRI) researchers.
AHRI postdoctoral fellow Dr Roberto Busi warns that Sakura® (Group K) is a great pre-emergence herbicide to control ryegrass, but using below-label rates poses a risk of rapid evolution of ryegrass resistance and should be avoided.
The pattern of rapid resistance evolution of Sakura® is similar to previous research into the use of low rates of diclofop-methyl (Group B) on ryegrass.
It is recommended Sakura® be used at full label rates and in rotation with other pre-emergence herbicides as part of an integrated weed management strategy that also incorporates non-herbicide weed control methods like harvest weed seed control and growing a competitive crop.
Key factors to consider when using Sakura® in 2013 for best results include:
- Use at full label rate of 118g/ha
- Rotate if used last year
- Best herbicide rotation is Sakura® (Group K) or Boxer Gold® (Group J & K) year one - trifluralin (Group D) year two (where trifluralin is still effective) - alternate Sakura® or Boxer Gold® year three
- Pre-seeding knock-down with glyphosate (Group M) and/or paraquat (Group L) soon after the break
- Harvest weed seed control is a critical component of an integrated weed management strategy
To develop a cost efficient herbicide budget, AHRI suggests growers consider using the more expensive herbicides at full rates over smaller areas and concentrating on doing a good job – rather than cutting rates over bigger areas.
Incorporating non-herbicide weed control tools makes the farming system more sustainable and paves the way for higher levels of cropping intensity.
Using a combination of herbicide and non-herbicide weed control practices will help to ensure a long term cropping future.
AHRI researchers presented the latest Sakura® trial results at the Global Herbicide Resistance Challenge conference and the 2013 Agribusiness Crop Updates in Perth in February. Reports are available at: www.grdc.com.au/UpdatePapers.
Further information about this research project is also available at www.ahri.uwa.edu.au, and in the March/April edition of Ground Cover, see article: Label rates lesson.
Dr Roberto Busi, AHRI
Professor Stephen Powles, AHRI
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