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.

Brome grass is one of the two “weeds-to-watch” for southern farmers.  The other is wild radish in its many combinations of herbicide resistance.

Brome grass swamping a fire break - a great source of weedsI talk about brome grass and not rigid or great brome, as I do not know anyone who can tell them apart in the paddock. In a lab under a binocular microscope, it is possible. For management purposes they should be considered the same species.

Brome grass is on the increase with the increase in minimum tillage because of limited availability of effective in-crop herbicides, delayed germinations and an ever expanding spread of herbicide resistant populations, particularly to Groups A and B. There are now 3 populations of brome identified resistant to glyphosate – two in South Australia and one from the Victorian Mallee.

The other problem is its ability to shatter. I passed a barley paddock near Kojonup, Western Australia, in late November which had a massive infestation of brome grass visible. When I passed the same crop two weeks later, most of the brome seed had dropped to the ground (see below). For harvest weed seed management to work here, the barley should have been harvested as soon as it was ripe.

Now you see it, now you don't - heavily infested barley crop where brome has shed after two weeks.Follow the link below to read a comprehensive interview with Chris Preston, University of Adelaide, regarding management of brome grass.

After a very relaxing Christmas we decided to head toward Esperance (W.A.) to spend New Year with some friends.

One thing that really stood out during the trip was how much fleabane was emerging from stubbles. Closer inspection of paddocks also revealed melons up to 50cm across.  

A healthy stand of fleabane regrowing after harvestYes it is sad that I noted this while on holidays, however this is the lot of an agronomist.

Some paddocks were visibly moisture stressed while others are looking healthy and growing actively.

All of these weeds germinated with the spring rains that have produced such good crops in southern Australia.

These weeds will be sucking moisture from the soil which can mean the difference between planting the 2014 crop on time or waiting for more rain. This will be particularly important for those earlier sown crops like canola and lupins.

Although harvest has just finished for some, and continuing for others across southern Australia these weeds must be dealt with as soon as possible.

A few reminders for good control in summer include:

• Don’t spray stressed weeds – this can be a combination of:
  • moisture – check plants are fresh and springy in the morning
  • heat – temperatures above 30°C can stop plants growing
• Control weeds as early as possible – size & stress
• Keep herbicide rates at the upper end of the label rate
• Keep application volumes and droplet size up
• Use the best quality water available – if in doubt have it tested
• Spray in the morning, but avoid still conditions which often mean inversions. Spraying at night might seem like a good idea but you have to deal with inversions and shifting wind directions

For more information see GRDC Summer fallow spraying Fact Sheet 

Here it is easy to see the fresh shoots post harvest

The GRDC now have 36 weed management videos on YouTube http://www.grdc.com.au/IWM-videos starting with the importance of weed seed capture at harvest and working through to use of double knock techniques to control hard-to-kill weeds.

The final five videos are clear explanations by Bill Gordon, spray application consultant, on how to make sure the herbicide gets to the target with sufficient coverage to maximise weed control and not waste your money.

Self propelled sprayer