It is now widely recognised that weeds adapt within a tillage system at various levels, and in various ways.
This specific issue was discussed at the recent Teagasc Enable Conservation Tillage Grass Weed Conference by John Cussans, weed biology and management specialist at the National Institute of Botany (NIAB).
Cussans confirmed that weed populations will adapt within all farming systems. While herbicide resistance is often the focus in discussions about weed adaptation, there are multiple layers to the issue.
“We do tend to obsess on herbicide resistance as a key way that weed populations are adapting to herbicide use,” Cussans commented. “Actually, we see adaptation on a number of different levels.”
According to Cussans, the adoption of minimum tillage and reduced cultivation intensity in the UK have played a key role in allowing weed populations to adapt within tillage systems.
This is part of a strategy that includes creating habitats for pollinators and protecting bird habitats and food sources. However, this seemingly positive change comes with unintended consequences.
Cussans highlighted a growing threat from invasive weeds due to these changes in cultivation practices, leading to biosecurity concerns.
Weeds traditionally not prevalent in the UK find hospitable environments in these habitats, becoming significant challenges.
How weeds adapt
The NIAB representative referenced the influence of different farming systems on different weed species.
He focused on the example of blackgrass in the UK, explaining how the spread of a specific farming system, rather than the weed itself, contributed to the proliferation of certain species.
“The system which encouraged the blackgrass spread to the north and to the west, and so the weed didn’t spread, the system spread,” he stated.
The third factor referenced by Cussans is the importance of understanding that within individual weed species, adaptation is not limited to herbicide resistance.
Using ryegrass as an example, he illustrated how weeds can adapt to key elements of the system, becoming more problematic.
Cussans also addressed the lack of regulation in the seed supply chain, leading to the unintentional introduction of problematic weeds onto farms in the UK, while he also urged farmers to be vigilant and proactive in dealing with these challenges.
Additionally, the NIAB representative stressed the importance of botanical skills and awareness.
