The Australian Glyphosate Sustainability Group has now added a searchable database to there highly informative site.
You can can now search for glyphosate resistance by:
This will give growers, advisers and policy makers the ability to get a better idea of where glyphosate resistance is occuring and how many populations have been found.
Currently it is best viewed in Internet Explorer and Chrome.
From my back of the drum calculations, the proportion of farmers regularly testing for herbicide resistance would have to be 10 per cent at most. Many will do it as a "one-off" but this really isn't good enough for managing herbicide resistance.
One of the main reasons there is a low usage of testing is because it was sold as a “you have resistance-you don’t have resistance” tool, which doesn’t tell the farmer much about management decisions needed to be taken.
A test for trifluralin resistance in annual ryegrass. An eye-opener. (image:P. Boutsalis)To be fair, this was reasonable when resistance was rare. Now it is widespread with many weeds resistant to many modes-of-action farmers need more.
Resistance testing must be seen as a positive management tool to give farmers the knowledge of what herbicides are still effective in each paddock. Regularly testing will enable better weed control and save money. Now who could ask for more than that?
Now which herbicides will control this ryegrass?The link below is an interview with Peter Boutsalis, ‘father’ of the Quick-test® where he outlines the major benefits of regular testing.
Here is a valuable article from the latest E-weed newsletter by Sally Peltzer and Alex Douglas, DAFWA.
Despite the rain in September in many areas of WA and southern Australia, there are still dry conditions in many regions.
It is tempting to stop any harvest weed management in the dry years. “There doesn’t seem to be many seeds on those annual ryegrass plants”, I can hear you say. That’s where you may be wrong.
Research by AHRI has shown that annual ryegrass seed numbers can still be relatively high in poor seasons (Table 1). These can carry over to the following year and reduce yields. Note the comparative ryegrass seed yields for the two seasons. Not much of a yield penalty for ryegrass in a drought year when compared with wheat.
Table 1: Wheat yield and annual ryegrass seeds produced over 2 years.
|
Year |
Wheat yield |
Annual ryegrass |
|
|
(t/ha) |
(plants/m2) |
(seed/m2) |
|
|
2011 |
4.0 |
19 |
12,000 |
|
2012 |
0.6 |
29 |
7,000 |
Cut your crop lower in a dry year to catch more ryegrass seeds.
In a good year with a big crop, there will be less light penetration and the annual ryegrass tillers will be upright and easier to catch. In a low-yielding year with a light crop and an open canopy, the ryegrass tillers will be also shorter. The work done by AHRI showed that at 40cm harvest height in 2011 (high yielding crop) collected about 60 per cent ryegrass seed at crop maturity compared to about two per cent in 2012 (low yielding crop).
The more seeds dropped in one year, the less crop yield in the following year.
To illustrate the difference in cutting height in a dry year, The Weed Seed Wizard has simulated wheat yields in 2013 after 7,000 annual ryegrass seeds/m2 were set in 2012. If the crop was cut at 10 cm, only 1250 ryegrass seeds/m2 are returned to the seedbank with a resulting 400 kg/ha of wheat yield loss the next season. This compares to a yield loss of 1.4 t/ha when the crop is cut at 40 cm and most of the ryegrass seeds are dropped.
Fig. 1 Effect of weed seed management strategy on crop yield and
weed seed numbers modelled with the Weed Seed Wizard.
Also in dry years where wheat yield is low, it is possible to burn narrow windrows in wheat. For wheat crops of 2 to 2.5 t/ha or less it is possible to burn just the windrows. Cutting low is imperative to keep the fire in the windrow.
A Great Southern (WA) vigneron, who was worried about his under-vine weed control, contacted me in early September. Sally Peltzer, DAFWA, and I paid him a visit to discuss the potential problem and to collect samples for testing.
For the past 20 years the vigneron had regularly used paraquat (L) under the vines rotated with glyphosate (M) and the occasional Basta® (N) application. As can be seen in the image the paraquat applied two weeks earlier has had little effect on the annual ryegrass.
Live samples were sent to Plant Science Consulting in South Australia to conduct Quicktests® to determine herbicide resistance status before the grass had set seed.
The results are back and yes the annual ryegrass is resistant to paraquat with a low level of glyphosate resistance in some plants. Seed will be harvested from test survivors for more detailed testing in 2014.
I am now discussing best management strategies now and the future with the vigneron.
This highlights the fact that rotating herbicide modes-of-action delays resistance and doesn’t prevent it. To prevent/manage herbicide resistance multiple tactics must be used in the ONE season to PREVENT SEED SET of any survivors.
Those vineyard managers and broadacre farmers rotating modes-of-action need to have a rethink of their weed management strategies.
