Policy for Injurious Weed Control

July 2024

The Mapperton Wildlands project has been underway since 2022 to help restore nature in West Dorset. Certain areas of the Estate, previously intensively farmed, have been taken out of arable production in stages following the harvest in 2021.  Other areas are now less intensively grazed resulting in a more varied grassland and flower rich structure.  The land is now grazed by low numbers of White Park cattle, Exmoor ponies, Tamworth pigs and our resident deer herds. 

Land that suddenly ceases to be under an arable crop is susceptible to a proliferation of plants that quickly colonise bare soil. Five of these are considered to have such a high nuisance value that they have been specified under the Weeds Act, 1959, and at least three of these have increased in abundance on some of the land within the Mapperton wildlands project, which has been a cause of concern to neighbours. 

The Estate has no wish for its re-wilding project to have a negative impact on neighbouring land interests. We have therefore drawn up and implemented the following weed control policy, based on the DEFRA Code of Practice 2004 and the policy developed by the Knepp Estate.

Injurious weeds

The five plants specified under the Weeds Act, 1959 are common ragwort Senecio jacobaea, spear thistle Cirsium vulgare, creeping or field thistle Cirsium repens, broad-leaved dock Rumex obtusifolius and curled dock Rumex crispus.  All these species are present on Mapperton Estate, but it is ragwort and to a lesser extent creeping thistle and dock that are most problematic. The control of weeds of disturbed ground is extremely difficult, even with the use of herbicides in some cases. Airborne seeds of species such as thistles and ragwort need only small patches of bare land on which to germinate successfully.  

The Injurious Weeds Act does not make it an offence for any of these five species to be present on land, but is primarily concerned with their control and prevention of spread. This document presents the Mapperton Estate Injurious Weed Control policy. It deals in greatest depth with ragwort, as this is known to be toxic to livestock.

Ragwort Common ragwort Senecio jacobaea is a native wild plant of the UK. It is also native to the rest of Europe as far a southern Scandinavia and reaches across to Western Asia and North America. It flourishes best on dry, bare or disturbed chalky or limy soils and grasslands although will grow on more acid soil. It fares least well on wetlands, scrub, woodlands including plantations, hedgerows and anywhere generally on acid soils. Ragwort forms a rosette of leaves and a taller flower stem that on average is 30-90cm. This means some plants will be smaller, but some will also be much taller when in ideal conditions. When in flower it is highly conspicuous. 

There are some seven other native species of ragwort Senecio spp., and about eleven other introductions that have either escaped from gardens or from sources such as wool shoddy.  Three of the native species are more familiarly known as groundsels. Some of the native species are extremely rare and protected or they have very limited distribution. Most of the introductions are also very limited in their distribution.  

Common ragwort is by far the most widespread and abundant of these species in Dorset. Although other species of ragwort – and common groundsel Senecio vulgaris – do contain similar alkaloids to common ragwort, these species are seldom present in sufficient quantity to constitute a threat to livestock.

Environmental benefits of ragwort (from DEFRA Code of Practice)

Seed distribution

The number of seeds produced per plant ranges widely, up to 30,000 per plant is cited by some authorities. Many plants will produce far less than this, especially as a variety of insects eat flowers and seeds; and some will produce more. Most, but not all, of these seeds have a hairy ‘parachute’ and are thus dispersed by wind. Most ragwort seeds, a figure of 60% has been calculated, fall around the base of the plant, and seedfall decreases with distance such that at about 36m (120ft), 0.005% seedfall occurs. This means that for a plant that does produce 30,000 healthy seeds, 18,000 land at the base of the plant; 11,700 seeds land 4.5m (15ft) away and so on until at a distance of about 36m (120ft), 1.5 seeds land. 

Ragwort is one of a large number of European plants that contain distasteful, toxic compounds in order to deter herbivores from eating them. The chemicals contained by ragwort are known as pyrrolizidine alkaloids. These are toxic to many mammals including livestock and humans, but are especially poisonous to horses and cattle, either fresh or in hay.  However, animals including horses, cattle and their ancestors have lived alongside ragwort in Europe, Asia and Africa for many thousands of years. The weblink Ragwort Facts http://www.ragwortfacts.com/index.htm gives further information on pyrrolizidine alkaloids and the plants that contain them. 

It is difficult to be definitive about numbers of seed, the spread of ragwort, and the number of livestock fatalities it causes. Those who call for ragwort to be eradicated will tend to cite the highest seed numbers, rate of spread, number of horses killed per annum and so on, and those who view ragwort as a valuable component of a native flora will tend to cite the lowest. To try to put ragwort into some kind of reasonable context, it is only one of a considerable number of plants that can cause horse and other livestock fatalities if consumed. In southern England, these include some common species such as foxglove, ramsoms, daffodil, cuckoo pint, ivy, white bryony, bracken, black bryony, elder, spindle and of course yew. Others, including bluebell, have also been known to poison horses although not fatally. 

Policy for control of spread of ragwort and other injurious weeds

As a precaution, all land adjacent to the Mapperton Wildlands Project boundary will be treated as though it were used for pasture or forage production, including private gardens. The strip of land to a depth of about 50m around the perimeter of the wildland area and around any tenanted or privately owned land embedded within the project area but not part of it will thus, if ragwort is present, constitute the High Risk Zone identified in the Defra Code of Practice. This c50m strip of land will be topped as necessary to prevent the spread by seeds of ragwort and other injurious weeds to reduce as far as practicably possible the presence of ragwort and other injurious weeds and to prevent their spread onto neighbouring land. Land 50-100m inside the Mapperton boundary, if ragwort is present, will be in the Medium risk category, and as such should never change from Medium to High because it is always going to be over 50m from land used as pasture or forage production outside the Wildland Project area.  Land over 100m from the boundary will be in the Low risk category and should remain thus even if ragwort does occur at some density. The use of herbicide is not favoured by the Estate, as this is contrary to the aims of the project. 

Control of ragwort and other injurious weeds will therefore be undertaken by means of topping, which will be done in July / beginning of August each year.  Topping earlier than this cannot take place because of ground-nesting birds.  Topping will be carried out every year as necessary, as ragwort and other injurious weeds may re-grow or re-colonise from the land outside the buffer zone on Mapperton Estate as well as from plants outside the estate.  We may also hand pull ragwort in additional areas from time to time.

Prior to this Policy, the following measures have been taken to prevent the spread of ragwort: Land where ragwort is present up to 50m inside the Estate boundary has been topped in July. Two heavily ragwort-infested fields around Mapperton have been topped. One field adjacent to a neighbouring farm in a Countryside Stewardship scheme, with horses has also been topped. The total elimination of all ragwort, creeping and common thistle, broad-leaved and curled dock from Mapperton Estate is not feasible and, as native wild plants with significant ecological importance, neither is it desirable or a legal requirement under the Injurious Weeds Act. 

This report is based on information and research considered to be of good scientific origin, and is understood by the Estate and those consulted to be fair and accurate at the time of writing. It has been compiled on behalf of Mapperton Estate, which is responsible for complying with UK legislation under the Weeds Act 1959. Any new information, provided that it comes from a reputable source, will be considered and any necessary adjustment will be made to the estate’s Control of Ragwort and other Injurious Weeds policy. 

The Estate will endeavour at all times to follow the Defra Code of Practice on ragwort control, and to control the spread of other species cited in the Injurious Weeds Act 1959. The Mapperton Wildlands Project is a legitimate use of land by its owner. As with all land usage and change, there are some that will be in favour and some that will not, and we will do our best to balance differing views and interests.

References:

Cooper, M.R. & A.W.Johnson, A.W. (1988) Poisonous Plants and Fungi HMSO.  

Grime, J.P., Hodgson, J.G. and Hunt, R. (2007) Comparative Plant Ecology Castlepoint Press.  

Salisbury, Sir E. (1964) Weeds and Aliens. New Naturalist No. 43, Collins 

DEFRA Code of Practice 2004 www.defra.gov.uk/farm/wildlife/weeds/pdf/cop_ragwort.pdf

For further reading on ragwort please visit the following site www.ragwortfacts.com/index.html