6. RESISTANCE TESTING WILL BE HELPFUL
RESISTANCE testing of the 197 samples against post-emergence contact herbicides shows considerable variability in resistance status.
For example, about 46% of samples are sensitive to both Atlantis (mesosulfuron + iodosulfuron) and Axial Pro (pinoxaden) meaning their use will be useful. But 47% of samples are confirmed as resistant and either probably or likely to reduce performance.
There are regional differences. In the North Yorkshire and Co Durham cluster, there is a much higher proportion of Atlantis ‘RRR’ resistance (40%) compared with Axial Pro (10%), yet in the South Yorkshire cluster it is the other way round, with just 6% RRR with Atlantis, compared with nearly 30% with Axial Pro.
Knowing your population’s resistance status will help make better management decisions.
WHAT DO THE CATEGORIES MEAN?
- S – Susceptible (over 81% control)
- R? – Early indications of resistance, possibly reducing herbicide performance (72-80% control)
- RR – Resistance confirmed, probably reducing herbicide performance (36-72% control)
- RRR – Resistance confirmed, highly likely to reduce herbicide performance (0-35% control)