Falling stock numbers in upland areas are seen as a major trigger for the rapid growth of the area of bracken in the UK, currently spreading at a rate of 100,000 acres per annum.
At a recent meeting of the Mull Monitor Farm, part of the national programme led by Quality Meat Scotland, beating bracken was described as "not a battle, but a war – you just have to keep on fighting it!"
Bracken control was the hot topic at the meeting at Torloisk Farm near Ulva Ferry, on the island’s western coast attended by over 50 farmers from Mull and the mainland.
Monitor farmer Iain MacKay took on a five year Short Limited Duration Tenancy (SLDT) on Torloisk, a 7,600 acre predominantly hill unit, in 2010. Prior to this he had contract farmed the unit since 2004, with help from his veterinary surgeon wife. Torloisk runs 50 pedigree Highland cows and 850 ewes.
Representatives from two bracken control companies, MFH Helicopters and PDG Helicopters, also attended the meeting at which a number of problems for farmers, including difficulty when gathering hills and shading out grass, were highlighted.
It is also toxic and harbours ticks which can transmit diseases like Louping Ill to sheep and Lyme disease to humans and can cause cross compliance issues.
It is an extremely tough and resilient fern and spreads rapidly underground via rhizomes. To kill the bracken, the rhizomes have to be destroyed, farmers at the Mull meeting were reminded.
Research suggests that there are two types of rhizome – superficial, surface rhizomes, backed up by deeper "storage" rhizomes which re-generate after what the plant recognises as attack of the surface rhizome.
The options for bracken control basically fall into two categories, physical - which includes cutting, crushing, stock trampling and chemical – weed wiping or spraying with tractor/quad mounted sprayer, knapsack or helicopter.
Previous generations, particularly in non-arable areas, cut bracken by hand for animal bedding. This cutting helped to control the bracken while also reducing the canopy, encouraging the growth of grazing vegetation.
Iain and Helen MacKay have employed numerous methods of trying to control the Torloisk bracken. "The first thing we did was to spray and crush to create access routes to help make the hill gathering easier," said Iain MacKay.
"There are no hill parks to hold sheep, so when we brought the sheep in at marking time, after releasing them, the young lambs were getting lost amidst the high bracken and risked being mis-mothered," added Helen MacKay.
A quad can take a sprayer and crusher where tractors cannot. "You must still be on the look-out for rocks, which can be really dangerous," observed Mr MacKay.
Feeding cattle with cobs amidst bracken, so their hooves would destroy the rhizomes, has also been tried at Torloisk. "This did work for a while and, as with crushing, enabled the vegetation below the bracken to grow," explained Mr MacKay. "But it was only temporary, the bracken soon came back. Also, of course, only relatively small and accessible areas are used for feeding cattle over the winter."
Crushing is most effective when the stems are both brittle and large enough to crush under the weight of the implement - during early frond growth, and should be done twice a year for three years.
If bracken is to be cut, it needs to be cut twice a year for at least three years. The first cut - when it is mature and has stopped growing – mid to late June, and then again six weeks later.
The two chemical treatments currently used are glyphosate (usually Roundup) and asulam (traded as Asulox).
The glyphosates affect almost everything, so should only be used with a weed wiper. Asulam is much more plant specific and can be applied by knapsack sprayer (adding food dye helps to identify which areas have been sprayed), tractor or quad mounted sprayer or helicopter.
Many of the sheer and high slopes of Torloisk are only accessible by the most nimble and brave human foot, greatly reducing bracken control options. The MacKays have identified the major problem areas to be sprayed by helicopter, while carefully avoiding water courses which flow down the steep slopes.
The cost of everything arriving on and leaving Mull, is inflated by across the water transport costs. By combining together last year a group of Mull farmers bought in a shipload of 900 tonnes of lime.
This spirit of co-operation has extended into eight Mull farmers, including Iain MacKay, jointly hiring in helicopter spraying services, helping to make the venture considerably more economic for each farmer than if they had acted independently.
While very few farmers now utilise bracken for livestock bedding, the recent enthusiasm for producing energy from natural resources has encouraged a small firm in Somerset to trial the harvest of dead bracken and convert it into low moisture content pellets, for burning in a biomass boiler to generate heat.
The next Mull Monitor Farm meeting will be held on 1st September.