Trials to Improve Understanding of Herbicide Resistance

Dr Peter Boutsalis, of the University of Adelaide, talks about herbicide resistance trials.

Trials in Victoria and South Australia

Knowledge about herbicide resistance is very important and the only way that we can get a good idea of what’s happening out there using an unbiased approach is to randomly select paddocks, collect weeds and then test for resistance. Since 2005 the GRDC has been funding us to do these trials and we’ve sort of moved right across the South Australian and Victorian cropping zone.

Just behind me here, I’ve got an example of all the brome populations that we’ve collected over the past five or six years. Each particular part is a single field. So this is one particular farmer field, and as you can see, there are a lot of farmer fields there. This brome is being well controlled with a lot of the herbicides.

But we also starting  to see there are some nice green in clumps and that indicates that these Brome populations are resistant. This kind of information can indicate to us where the problems are and this helps chemical companies focus their research ideas and try to extract most of the information so we know that is a lot of resistance in ryegrass.

In Brome it’s not as common, resistance, but it is coming and we have to be prepared and be proactive before the problem gets out of hand, like it has for ryegrass in previous years. Traditionally we’ve been using a single herbicide. Trifluralin, Boxer Gold Sakura and various other herbicides and so what we are thinking and farmers are doing it as well, we are trying to be more innovative and try and mix herbicides to try and extract the most activity out of different herbicide mixtures so we can get the best performance.  So Brome is becoming a very big problem because of no till farming and because of the limited amount of herbicides that do control Brome.

Testing Different Herbicides

So, here in this trial we’ve got up to 50 odd different herbicides, individual herbicides and herbicides combinations to try and get indications of which ones may be really effective in the field. Also some of the herbicides we have used in here are confidential but they aren’t actually registered in australia so we are working with private industry to test new active ingredients to see if any of these can be really useful to farmers not only as a single product but also in mixtures with existenting products.

One of the most important pieces of equipment what we have is this laboratory sprayer where we can control the nozzles, the water volume, the speed, to some extents, really create paddock conditions, obviously without the wind. We always use agricultural nozzles not all the farmers are using out there.

So we try to replicate the spraying conditions as much as possible. Anything that sort of survives our herbicides in this conditions we can be very confident are herbicide resistant. So we really try to help farmers control resistance by increasing the amount of different active ingredients to try and control the weeds