It has been a slow acceptance by many farmers that blackgrass is a problem in Ireland.
Many of us have visited farms in the UK and listened to their issues dealing with the weed.
The gravity of the problem was clear to see and the continued struggle these UK farmers faced year on year resonated with Irish farmers.
However, each and every Irish farmer was glad it wasn’t their problem, and with this came a level of despondency.
Blackgrass has now been identified in all major tillage counties from Donegal to Cork and everywhere in between
If the weed is not a problem in the locality, never mind on the home farm, then real engagement with understanding the problem may not have been as strong as it could have been.
This has changed beyond belief within four to five years.
Blackgrass has now been identified in all major tillage counties from Donegal to Cork and everywhere in between.
The Enable Conservation Tillage (ECT) project, led by Teagasc, has been working with a number of farmers to guide them through the process of getting on top of blackgrass populations.
There are a number of key factors, which a farmer must take on board if blackgrass is to be brought under control. These include early detection and action and developing a zero-tolerance approach. This is the best and cheapest from of control. Where blackgrass is on your farm:
Elimination of the weed should be the goal but this may take five to six years to achieve.
A number of farmers are going through the eradication process on their farms at the moment and their experiences provide valuable learning for everyone.
In the following cases, the farmers’ identities have been kept anonymous. The case studies show both best practice in terms of dealing with blackgrass and the consequences of not taking the weed seriously.
A plough-based farmer in the south of the country discovered a small patch of blackgrass in his winter barley about five years ago.
While it seemed like a small patch, there were also some scattered plants spread through a 10ac block. The farmer burned off the small patch immediately and hand-rogued before seed set.
The farmer was very persistent in hand-roguing to make sure no plants set seed each year
Immediately after harvest, they carried out stale seedbeds and the rotation was changed to spring cropping. A key crop in this rotation was spring beans as both spring drilling and alternative herbicides contribute to blackgrass control.
The farmer chose to grow spring barley for the next four years in combination with stale seedbeds and hand-roguing. The farmer was very persistent in hand-roguing to make sure no plants set seed each year. It’s five years since that farmer detected blackgrass and the weed is now all but eliminated. However, the farmer remains vigilant and continues to walk the field four to five times a year looking for any plants which may emerge from shed seed.
A minimum-tillage farmer in the ECT project who had a high level of blackgrass on an outfarm has been working through the problem over the past three years.
Interestingly, the farmer’s own attempts to identify the blackgrass, with the help of agronomists, led to misidentification of the weed. This, in turn, delayed the start of control for a number of years and allowed blackgrass to spread, resulting in a much bigger problem.
He believes the likely source of the seed was from perching birds
However, the farmer was able to identify the most likely source of the problem.
The weed was first identified in the centre of the field underneath electric wires.
He believes the likely source of the seed was from perching birds who eat from a grain screening pile from a nearby facility and dropped seeds in this spot.
The solutions identified for eradication of the weed are much the same as the first example although the option of putting the field into grass for a number of years was debated with the farmer.
The ECT team continues to monitor the blackgrass populations and is tracking the effect of control measures.
In 2019, the average blackgrass plant count was 21 plants/m2 and this reduced to an average of 11 plants/m2 in 2020. This is a 52% reduction. There appears to be a similar reduction in plants in 2021 (we are currently analysing the data).
There is still one area of the field, however, with very high levels of blackgrass. If left untreated this will allow seed return and spread.
Burning off of this area with glyphosate before the weed sets its seed was the best solution for that patch. A reassessment of the rotation is also ongoing and the farmer continues to put in place all possible cultural practices on the farm.
The message from this farmer is that early identification is critical and a large weed infection will take well over five years of constant management to eradicate.
The ECT team visited a plough-based farmer in the northeast of the country and were immediately struck by the high levels of blackgrass present as they entered the first field. The populations of blackgrass were three to four times that of the drilled winter wheat.
The agronomist working with the farmer was hugely concerned as the problem had been building on the farm for the past five years (or possibly more). A tour of the farm revealed blackgrass in most fields at alarmingly high populations.
A limited rotation was used on the farm which consisted of winter wheat, barley and oats.
The sheer level of blackgrass on the farm showed this strategy has not worked and the ECT team also had concerns about possible herbicide resistance in some populations
The ECT team was again struck by the level of blackgrass in the field margins, roadways and around the farmyard.
Despite receiving good advice to help control blackgrass, the farmer hadn’t taken the problem seriously. He was adamant his rotational system worked for him and the available herbicides would be sufficient to achieve control.
The sheer level of blackgrass on the farm showed this strategy has not worked and the ECT team also had concerns about possible herbicide resistance in some populations.
Seeds were subsequently grown and tested for herbicide resistance in Teagasc, Oak Park.
As feared, the population was confirmed to have multiple types of herbicide resistance.
The ECT team and agronomist spent a considerable amount of time with the farmer going through the actions which would help his farm.
The first one was to put the entire farm into grass for a number of years. While the farmer listened, he was still reluctant to make significant changes.
Worryingly, by continuing to grow this level of blackgrass on his farm there is a high risk weed seeds will spread on machinery, straw, wildlife, etc, to neighbouring farms.