Date: August 22, 2023
Shay Phelan
Journal: Irish Independant
Eventually there has been a couple of dry days where harvesting can be carried out and straw baled, there has been a lot of frustration on farmers behalf with the weather, the yields, quality and new regulations. It has been a harvest that most, now, just want to get finished as quickly as possible and move on to 2024 crops.
Planning for harvest 2024 has already begun with winter oilseed rape drilling already under way. While oilseed rape ticks a lot of boxes for many farmers including the two and three crop rule which will be in force for 2024, there were a few issues with it in 2023, including clubroot, so choose your fields carefully. This does not only apply to oilseed rape but it also should apply to other crops especially where grass weeds are an issue.
In 2023 we have seen a huge increase in the reporting of blackgrass, Italian ryegrass and other grass weeds around the country. These fields are the ones that you should plan your rotation around as we are seeing the these weeds are becoming more and more difficult to control. At the risk of beginning to sound like the boy who cried wolf, this problem is increasing all the time and our reliance on herbicide control alone is beginning to fail.
In Oak Park, we are continuing to test weed samples, including grasses, for resistance and some of the results we are seeing are now quite scary. Take black grass for example, we now have many different populations in Ireland now which have developed resistance to multiple herbicides including Pacifica Plus, Monolith, Stratos Ultra, Falcon, Centurion Max, Astrokerb and lately we have sen a population with reduced sensitivity to glyphosate meaning this population will need high rates of glyphosate to kill it. So my question to anyone dealing with blackgrass what is your plan to control it? Do you sow a crop and hope for the best or do you switch to spring cropping and use cultural methods to control it? My fear, listening to some commentary from around the country, is that many people have a very relaxed attitude and will continue as normal. I was told by a farmer recently, that a neighbour who had blackgrass was told by his advisor to make sure to bale the straw and get it off the farm, while another assured his client that the blackgrass was under control and wouldn’t be a problem in 2024.
It was however heartening to see some farmers take the time to get samples tested for herbicide resistance and then build a plan around that information but most have not. These will simply continue to use herbicides that claim to give control and if that fails then will burn it off with glyphosate before the seeds are viable. Bear in mind this approach has failed in the UK and that all the costs on the crop, circa €2,000/ha, will be spent at that time, with the exception of harvest costs. That’s a very expensive gamble. Common practice in the UK now is to use multiple active ingredients, or stacking ingredients, with costs are running into almost €400 /ha, for grass weed control alone and they still can’t eliminate it.
In June as part of the IPMWorks project, I travelled with the group of the participating farmers to visit cereal farmers in Denmark to investigate some of their Integrated Pest Management (IPM) techniques in dealing with grass weed issues. On the farmers we visited, herbicide resistant Italian ryegrass was the biggest problem that they all had to deal with. They also had blackgrass and resistant annual meadow grass but the Italian ryegrass is their biggest worry as it can develop resistance to a herbicide within 4 years of repeated application of the same active ingredient. To deal with the problem they are using as many different IPM techniques as possible such as crop rotation, increased seed rates, stale seed beds, rotational ploughing, delayed drilling, rogueing etc. to try to reduce the populations in fields. When they have no other option, as populations become too high, they simply put the field into grass and swap it with the local dairy farmer in return for one of their fields, for five to ten years.
Again, here in Ireland we have populations of italian ryegrass which are also resistant to many herbicides, we have wild oats that are resistant to Axial Flo, and we also now have discovered annual meadow grass that is resistant to als herbicides e.g. Pacifica Plus. Plan to use the different IPM techniques to control these problems starting now, probably, with stubble cultivations. Spring cropping offers the opportunity for an extra cultivation or two to try to get as many weeds to grow as possible.
One of the main goals of the IPMWorks project is to look at alternative methods of controlling different pests in light of the targets set down by the EU commission of reducing the use of chemical pesticides by 50% by 2030. This will no doubt further restrict the numbers of herbicides that are available and in turn will increase the likelihood to resistance developing to many weeds including grasses. What was obvious in Denmark was that those who took action early and used crop rotation and other tools were able to control grass weeds better than those who continued with the same cropping system.
The Teagasc herbicide testing service based here in Oak Park, is free and available to anyone who wants to avail of the facility. We are not just looking for grass weeds we are also looking for broadleaf weeds also. A few of the famers and advisors who have used the service have found it very useful in helping them to make decisions. Without this information and without taking early action against grass weeds, we might find ourselves, like our Danish friends, looking for the number of the nearest dairy farmer.