The Teagasc Grass Weed Conference which is underway today, Wednesday, November 8, represents the culmination of the five-year Enable Conservation Tillage (ECT) project.
The accompanying report highlights a number of recommendations, relevant to both inversion and non-inversion tillage systems, where the control of herbicide-resistant grass weeds are concerned.
But as Michael Hennessy, head of Teagasc’s Crops Knowledge Transfer Department, pointed out, there a number of ‘take-home’ messages from ECT that should resonate with all tillage farmers.
Grass weed control
Firstly, the challenge of herbicide-resistant grass weed does exist in Ireland. However, steps can be taken to control these weeds effectively and minimise their production impact within tillage crops.
“Farmer awareness is the critical first step,” Hennessy said.
“Growers must know which weeds to look out for and to step in with control measures as quickly as possible.
“Initially, hand roughing prior to seed setting may be all that’s required. Additional steps can be taken in cases where the problem has developed beyond this stage.
“But the worst of all worlds is the development of grass weed populations that have multiple herbicide-resistant traits, he added.
In these instances the only option available may be to revert fields back to grass leys according to the Teagasc representative.
“Regular grazing or silage cutting over a concerted period of time will help to reduce resistant seed banks that had previously built up in the soil,” he said.
Ensuring that imported machinery is adequately cleaned will stem the threat of resistant grass weed infestations coming into the country.
But as Michael Hennessy pointed out, this is akin to shutting the stable door after the horse has bolted.
“The reality is that the challenge of herbicide grass weed resistance is already with us,” he explained.
“So, machinery moving from field or from farm to farm has the very real potential of escalating the problem still further. And this is an issue that farmers and contractors will have to address.”
ECT project
The work carried out under the aegis of the ECT project has highlighted a number of key points.
All tillage systems, both plough and non-plough, can be operated successfully while keeping grass weeds to a minimum.
An ECT survey has confirmed that grass weeds are an increasing problem in all tillage systems.
Non-plough regimes tend to have better rotation, do more stale seed beds and use higher rates of herbicides.
However sowing dates tend to be earlier and higher where weed burdens are apparent, specifically where bromes and Italian Ryegrass (IR) are concerned.
Moreover, a greater level of herbicide resistance in IR populations is more prevalent within non-plough systems.
Herbicide-resistant grass weeds such as blackgrass and IR are increasing. Where there is multiple resistances within the same population, crop production becomes almost impossible.
All farmers must be vigilant to stop the entry or spread of the weeds into their farms.
Spotting a problem early and hand roughing before seed set is the best policy.
Where weeds are established, growers should consider very aggressive tactics, including crop burn-off and grassing down, to prevent further spread.
ECT project focus farmers have shown the way in how to reduce weed populations. But they were also brave enough to share their experiences, which led to population to build-up.
Methods
Good rotation is essential according to Teagasc. Growers should avoid successive winter barley crops within non-inversion. Such an approach will lead to increases in sterile brome populations.
Growers should utilise different herbicide types. Grass margins can work extremely well to control grass weeds.
Rotational ploughing should be considered in non-plough systems where the weed burden is very high.
Growers should use pre-emergence herbicides, where possible. An over reliance on post-emergence products will increase the risk of developing herbicide resistance.
And finally, non-inversion – direct drill relies on a degree of flexibility in our system to cope with wet conditions. Given these circumstances, an element of light cultivation may also be necessary.