Chemical Management of Bracken ~ Summer 2016

Monday 11th July 2016

Toll's Hill Fields; restored grass & heathland species ~ © BareFoot PhotographerToll's Hill Fields; restored grass & heathland species ~ © BareFoot Photographer

Although some Bracken is good it is a very dominant plant and, if not controlled, it will take over the landscape; suffocating many of our other wildflowers which are not as fast growing. Throughout Scilly's history Bracken has been used by locals in various ways; i.e animal bedding, fuel, packing materials, but as this now happens less and less the way that Bracken is managed also needs to change.

“We will never remove all of the Bracken; we wouldn't want to as it is a part of the ecosystem and small pockets can provide shelter for some species, but it is important that our smaller, less aggressive plants are supported and able to continue to thrive.”  

Best practice guidelines state that the primary method for Bracken management should be mechanical control, when Bracken is in full growth, with grazing acting as a complimentary tool once the mechanical process has been established. Over time as the Bracken is weakened less cutting should be required.

Past Bracken management utilised grazing animals as the primary method of control (due in part to available resources) which has resulted in a slowly developing understory of grasses and wildflowers; however, these continue to be dominated by a canopy of bracken during the summer months.

In more recent years the Trust has been following best practice guidelines, mechanical control complimented by grazing; with the best time to cut and weaken Bracken being between June & August. These cuts can however coincide with the flowering of common and nationally scarce species (i.e. Cat’s ear and Balm-leaved figwort) and as a result continued ongoing mechanical control could be seen to be in conflict with our aim to improve biodiversity in the long term.

Additionally in some areas cutting and grazing has started to produce the desired outcome and further cutting does not seem to be impacting on the remaining Bracken; in these cases an alternative to cutting has been investigated and identified.

Chemical control of Bracken is not only recommended but also falls under best practice guidelines, with the chemical of choice being Asulox (active ingredient Asulam) a selective herbicide that targets only Bracken, and in some instances other fern types.

How will it be done?

Asulox is selective herbicide which our Ranger Team will be applying in the seven areas detailed below sometime during the next 6 weeks,  using knapsack sprayers; the reasons for this method of application being threefold:

  1. It will ensure more accurate application, ensuring herbicide is not wasted on non-target plants;
  2. It will minimise the impact of chemicals being released into the environment
  3. It will also reduce the amount of chemical used in each target area.

Not only being more environmentally sound but also having financial benefits, which is an important consideration for a charity with a limited income.

Although Asulox is a selective herbicide we feel it is most appropriate to ensure the least amount of chemical discharge and contamination in the areas being treated; hence the use of knapsack sprayers.

Our chosen method of treatment requires very specific weather conditions and as such the areas being treated will be worked on at short notice.  Fences will be erected and posters will be displayed around the areas during the treatment, and for a 24 hour period following the treatment, but no footpaths will be blocked during this process.

Asulox is an irritant and may cause irritation if it comes into contact with skin; as a result of this, to ensure that the chemical has the best chance of working and to avoid contamination of other sites, we are asking that people do not enter the areas being treated for a 24 hour period following the treatment. Please ensure that pets and livestock are also prevented from entering the treated areas for their comfort and safety.

For more information regarding the areas being treated and the reasons for treatment please see below.  Treatment will take place when weather conditions are appropriate; maps of each site are available through links at the end of the area description):

Site 1 - Bant’s Carn

Grazing at Bant's Carn ~ © BareFoot PhotographerThe reason for treatment of this area is two-fold:

  1. The rhizomes of the Bracken are under-mining the Bronze Age field system boundaries and continued use of machinery could also damage these features.
  2. The grassland also holds important species such as Heath milkwort and the scarce Bird’s-foot, which have returned due to the grazing management of the site.

Continued cutting over the last few years has not reduced the Bracken further and so an alternative method is required.

A map of the area being treated can be viewed here

Site 2 - Innisidgen

The reasons for treatment in the area of heathland and the plantation is to protect the trees from damage by the Bracken and to remove the invading Bracken from the plantation and regenerating heathland below.

A map of the area being treated can be viewed here

Sites 3, 4 & 5 - Salakee, Toll’s Hill & Fields

Salakee Site A - This site has an established heathland sward that is being encroached by invading Bracken which needs to be stopped before it gets firmly established and takes over.

A map of the area being treated can be viewed here

Salakee Site B - This site has recently been cleared to prevent encroachment onto the waved heath below, this is an important habitat on Scilly.

A map of the area being treated can be viewed here

Controlling the encroachment of Bracken earlier will enable us to keep the site clearer in preparation for re-seeding with further Heather.

Toll’s Hill – Bracken is being managed and controlled on Toll’s Hill to prevent further encroachment onto the fields below; as the site has regenerated quickly it could now be enhanced further by grazing. Removing the Bracken now will reduce the amount of cutting and will enable us to graze, re-seed and clear further areas sooner on a site that has some great heathland indicators such as Heath bedstraw and Heath grass.

Toll’s Hill Fields – The grass/heath mosaic is now well established but Bracken is beginning to encroach from Toll’s Hill; control is needed in order to stop the Bracken swamping the field and damaging the grass and heath species which are currently doing well.

A map of the area being treated can be viewed here

Site 6 - Mount Todden

Mount Todden ~ © BareFoot Photographer

This site has regenerated quickly and can be enhanced further by grazing.

Repeated cuts of the Bracken may be detrimental to the grassland if continued so it is considered now is the best time to remove the Bracken by chemical control in order to least effect the grassland and ensure a healthy environment where grazing can take place.

A map of the area being treated can be viewed here

Site 7 - Gugh

The reason for treatment in this area is the large increase in Babingtons leek and Balm-leaved figwort since cutting of Bracken has been taking place. Continued cutting in the future may have a detrimental effect on these locally rare and nationally scarce species.

A map of the area being treated can be viewed here

There are strict regulations and guidance around obtaining and using Asulox; these have been adhered to by the Isles of Scilly Wildlife Trust. Chemical treatment of invasive species is a standard practice in land management and is used by other environmental NGO’s (non-governmental organisations) and farmers across the UK.

  • We always carry out a survey prior to cutting and land management to ensure that there are no breeding birds which could be effected.
  • Treatment may be carried out in other areas in future years subject to success rates and availability of resources.

If you have any queries or concerns regarding this or any other work carried out by the Isles of Scilly Wildlife Trust please do not hesitate to contact us.  Our contact details can be found here.