One population of great brome, meadow brome and three populations of sterile brome have been shown to be resistant to ALS-inhibiting herbicides (mesosulfuron+ iodosulfuron and pyroxsulam) in the UK.
One population of rye brome was shown to have increased tolerance to ALS-inhibiting herbicides.
These results, published in Pesticide Management Science this month, originate from an AHDB project: Investigating the distribution and presence, and potential for herbicide resistance of UK brome species in arable farming. The research was carried out by ADAS and Rothamsted Research.
ADAS senior research consultant, weed biology, Dr Sarah Cook says the good news is that all brome populations tested were sensitive to propaquizafop, although resistance to propaquizafop and cycloxydim in sterile brome was identified in Germany in 2012.
Glyphosate control
Additionally, all bromes tested were still controlled by 360g a.i/ha of glyphosate, although some populations showed increased tolerance at this rate. All populations were well controlled by 540g a.i/ha of glyphosate, the recommended field rate for annual grass weeds, says Dr Cook.
The results indicate that although ALS resistance is evolving in brome populations, other modes of action can be used to control these populations in a diverse rotation. But growers should be alert to the risk of the evolution of rapid herbicide resistance to other modes of action in UK bromes, according to Dr Cook.
Responding to the research findings, Bayer market development manager for cereals in North Europe, Roger Bradbury says that the number of UK brome populations in which resistance to ALS-inhibitors has been detected and confirmed to date is relatively low.
"But there is good reason to be vigilant. The samples were from geographically diverse locations meaning it is likely that resistance has evolved independently in these field populations. Growers can help limit further spread of resistance by using an integrated weed management strategy across the rotation to protect the chemistry available."
Solution
He adds that as yet, other key herbicides for brome control are not known to be affected by resistance. Mr Bradbury expects that Roundup (glyphosate) pre-planting and Liberator (flufenacet + diflufenican) pre-emergence as well as ALS-inhibitors post-emergence will continue to be part of the solution for brome control.
"Within an integrated control strategy, maximising herbicide performance is critical to minimising resistance risk. There are four main factors farmers should keep in mind. Apply products at the correct timing and use the full label dose, focus on application quality to get best coverage of the target and finally make sure that application conditions favour herbicide performance such as during periods of active growth for post-emergence products," says Mr Bradbury.
What farmers should do
- If you have poor control of bromes this season map the patches and identify the species.
- Populations with suspected resistance can be sent to ADAS Boxworth, Boxworth, Cambridge CB23 4NJ this autumn.
- Identification of bromes can be tricky but there is a useful leaflet by Dr Stephen Moss - Identification of brome species - available on the CROPPROTECT website.
Source: Dr Sarah Cook, ADAS.
