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Asulam is the active ingredient in the product Asulox.  It is no longer approved for use in the UK or in Europe. 

After the registration of Asulox was withdrawn at the end of 2012, the Bracken Control Group applied for annual Emergency Authorisations, which covered all of the UK, to keep Asulox available for bracken control.  

The annual applications were successful across the UK, up to and including the 2022 season, but only for England in 2023.  

On the 13th October 2023, UPL Europe Ltd., the manufacturers of Asulox, announced their decision to cease the research programme that aimed to prove that the use of Asulox was safe and effective for bracken control and allow the reinstatement of full regulatory approval (now under UK regulations).  A link to the UPL letter confirming this can be found here. 

Without the support of this research programme, a further application for an Emergency Authorisation for 2024, and beyond, could not be submitted.

Asulox in 2023

The application for Emergency Authorisation for the use of Asulam for bracken control during 2023 was approved in England only.

The full approval is available to download and this contained the latest version of the product label.

The dates included in the approval were as follows:

19 Jun 23 Emergency Authorisation issued Storage, promotion, sales, and transfer authorised.
1 Jul 23 Application of Asulam can commence.
11 Sep 23 Expiry date: for sale & distribution and use of stocks. Storage of stocks can continue, and stocks can be moved for disposal.  Asulam cannot be applied after this date.
27 Oct 23 Expiry date: for  storage and disposal of stocks. It will be illegal to store Asulam after this date.


Scotland, Wales and Northern Ireland refused to approve the application. Further information was provided:

Refusal letter for Wales & Scotland for Asulox 2023 (PDF)

Refusal letter for Northern Ireland for Asulox 2023 (PDF)

Hazel Dormouse

The Asulox approval for 2022 stated that “to protect mammals, application is not allowed where the hazel dormouse is known to breed”. This restriction applies to asulam application from the air and ground.

Additional guidance has been issued by CRD & Natural England and can be viewed here.  As there are very few confirmed records in Scotland, this guidance only applies to England.

Alternative Herbicides

The loss of Asulox is recognised as a major blow for those who wish to control bracken, and this brings into focus the search for an alternative to Asulox.  

This process started in 2012, with the establishment of the National Bracken Chemical Control Trials (NBCCT).  Reports on these trials are included under the Research menu of the website and key findings have been summarised in Bracken Briefings 13 & 26.

There is no alternative chemical control option available immediately, and this leaves areas of the country, where physical control methods (such as: cutting, bruising, rolling, ploughing) are not suitable or safe, without a valid bracken control method.

Alternative Herbicides - Glyphosate

Glyphosate (marketed as RoundUp®) is a non-selective, organophosphate pesticide, which is used widely to protect crops against weeds.

Its high solubility in solvents, especially water, and high mobility, allows the rapid leaching of the glyphosate into the soil leading to contamination of groundwater and accumulation in plant tissues.

Glyphosate was included in the NBCCT.  It had the lowest level of control on both fronds and rhizome systems, and had the greatest and longest negative impact on the ‘non-target’ habitat attributes.  See the National Bracken Chemical Control Trials 2012 – 2020 Final Summary Report - available in Research Reports under the Research menu.

For England, the Rural Payments Agency issued guidance on 9th April 2024 stating that Glyphosate may be used to satisfy the requirements of a Countryside Stewardship (CS) agreement, as an alternative to Asulox, if such use is approved by Natural England or the Forestry Commission.

In view of the potential for long-term damage to soil and non-target species, it remains to be seen whether Natural England or the Forestry Commission will authorise the use of glyphosate for bracken control as part of CS.

Glyphosate may have a role for carefully planned, small-scale control of bracken, but the side effects must be considered before application takes place.

Bracken Control Using RoundUp® Products.   Bayer, the owners of  RoundUp®, issued a Technical Bulletin in 2022 covering the use of the product for bracken control. The views expressed are Bayer's own and are not necessarily endorsed by the Bracken control Group.

An experimental approval (Extrapolated Trial Permit) for the application of glyphosate from a drone may be approved during the first half of 2024.  For background information about the use of drones, see Bracken Briefing No.24.

Alternative Herbicides - Amidosulfuron

Amidosulfuron (marketed as Squire Ultra, amongst other products) was introduced around 1992 for the control of broad-leaved weeds in cereals, linseed and grassland.

Amidosulfuron was also included in the NBCCT.

If applied at the same time of year as Asulox, (July-August) outside the bird breeding season, there are questions about the effectiveness of amidosulfuron for controlling bracken.

If applied early in the season (May-June), amidosulfuron has the potential to achieve moderate or good level of control over a three-year period but with a significant negative impacts on both the diversity and structure of the habitat involved.

For more information see Bracken Briefings Nos.14 & 15 and the ADAS Report: Comparative assessment of risks of two bracken herbicides - available on the Research Reports page.

Bayer, the manufacturers of Squire Ultra, has announced that it will not be producing the product after the end of 2024. Therefore, it will not be possible to complete a bracken control programme starting in 2024 that uses Squire Ultra.

In view of the concerns about the side effects, the questions about its efficacy and the lack of long term availability, the use of amidosulfuron products to control bracken is not recommended.