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Bayer Assist

For friendly informed advice about Bayer CropScience products, please call Bayer Assist free from UK landlines on:

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Cereal Herbicides 

Resistance Management  

Resistance Management

Herbicide Resistance Management

Many farmers now have herbicide resistant populations of grass weeds on their farms. In some instances these resistant grass weeds have been introduced from other locations by the movement of "contaminated" farm equipment etc. However, in most cases resistance will have developed on the farm over a number of years due to the over reliance on a restricted range of chemical control measures. This results in the selection of individual plants that are able to survive the herbicide. With repeated selection these resistant plants survive and multiply until they dominate the population.

Two major forms of herbicide resistance occur in the UK. The most common "Enhanced Metabolism Resistance" (EMR) results in plants being able to breakdown a range of herbicides with different modes of action. This form of resistance is partial leading to poor weed control. The other major type of resistance is "Target Site Resistance" (TSR) where the site of action of the herbicide is effectively blocked in the resistant plant. As such the herbicide is totally ineffective and the plant is completely unaffected by the herbicide. Two types of TSR have been identified in the UK. One affects "fop" and "dim" herbicides (e.g. clodinafop, fenoxaprop etc.) which inhibit the enzyme ACCase and the other affects sulfonylurea broad-leaved weed herbicides (e.g. mesosulfuron-methyl) which inhibit the enzyme acetolactate synthase (ALS)

Atlantis WG is an ALS inhibitor which provides high levels of grass weed control. As such, if used as the sole means of weed control, it would impose a high selection pressure on grass weed populations which could lead to the rapid selection of resistant individuals. These would then build up rapidly over time if no other measure was taken to control them and the field efficacy of Atlantis WG would be reduced. Whilst no target site resistance to ALS inhibitors has yet been identified here in the UK it does occur in grass weeds in other countries. Consequently the development of Target Site Resistance (ALS) in grass weeds in the UK must be considered a real threat to the long term field performance of Atlantis.

In order to minimise the risk of resistance development to Atlantis WG in grass weeds such as black-grass and rye-grass it is essential that the Atlantis WG Resistance Management Strategy is followed at all times. The key elements of this strategy are :

Hit 'em hard and Hit 'em early

  • Treating weeds when small and actively growing with an effective rate of Atlantis WG will maximise the control of resistant weeds.
  • To achieve this always apply Atlantis WG at 400 g/ha in tank mix with biopower (1L/ha), ideally at the 1-3 leaf stage of the grass weed

Use in association with effective products with different, non-ALS, mode of action

  • Always use Atlantis WG in tank mix with an effective non-ALS residual partner
  • Do not use Atlantis WG as the sole means of weed control in successive crops.
  • Always use non-ALS herbicides throughout the cropping rotation

Monitor effectiveness

  • Always investigate any odd patches of poor control. If unexplained then a resistance test may be appropriate