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Policy
for Injurious Weed Control on Knepp Castle
Estate.
By
Theresa Greenaway, 21st October 2008
Knepp
Wildland Project The
Knepp Wildland Project has been underway
since 2001. Most of the Estate, previously
intensively farmed, has been taken out of
arable production in stages since 2001. The
reasons behind the decision to abandon
intensive farming in favour of re-wilding
are given in depth in the Knepp Castle
website. The land is now grazed by low
numbers of longhorn cattle, Exmoor ponies,
fallow deer and Tamworth pigs.
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 Knepp
wildland project, which has been a cause of
concern to neighbours. This resulted in
representation being made to the estate by
Shipley Parish Council in 2008.
The
estate has no wish for its wildland project
to have a negative impact on neighbouring
land interests. We have therefore drawn up
and implemented a weed control policy to
reassure those who are unhappy with the
level of nuisance weeds that at the same
time will not compromise the rationale
behind its own aims for the land.
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
Knepp, 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 Knepp
Castle Estate Injurious Weed Control policy.
It deals in greatest depth with ragwort, as
this is known to be highly 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.
In
Sussex, excluding the groundsels, only two
native species of ragwort and one
introduction are likely to be encountered to
any extent. Common ragwort is by far the
most widespread and abundant of these; hoary
ragwort Senecio erucifolius is also fairly
frequent and dose occur on Knepp and the
wider countryside in field margins, verges
and other grasslands, although it prefers
base-rich soils. Marsh ragwort Senecio
aquaticus may grow on marshy ground near
rivers and streams. The introduced Oxford
ragwort Senecio squalidus grows on waste
ground, walls, railway embankments and
similar places. 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.
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 actually 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 highly
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 Factshttp://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.
Knepp
Castle Estate Policy for control of spread
of ragwort and other injurious weeds.
- As
a precaution, all land adjacent to the
Knepp Wildland 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 (see
map) 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 Knepp 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, as well as not being
compatible with the aims of the Wildland
project, is not permissible within the
terms of the organic status conferred by
the Soil Association www.soilassociation.org/certification.
Control of ragwort and other injurious
weeds will therefore be undertaken by
means of topping, which will be done at
the end of 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
KCE as well as from plants outside the
Estate.
- Prior
to this Policy, the following measures
have been taken to prevent the spread of
ragwort:
- Land
where ragwort is present up to 100m
inside the Estate boundary has been
topped in August.
- Two
heavily ragwort-infested fields near
Shipley have been topped.
- Three
fields adjacent to a neighbouring
alpaca farm were topped.
The
total elimination of all ragwort, creeping
and common thistle, broad-leaved and curled
dock from Knepp Castle 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.
Indemnity
This
report is based on information and research
considered to be of good scientific origin,
and is understood by the author and those
consulted to be fair and accurate at the
time of writing. It has been compiled on
behalf of the Knepp Castle 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. This policy has been
read by other organisations including
Natural England and other members of the
Knepp Wildland Project Steering group.
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 Knepp Wildland 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.
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
www.defra.gov.uk/farm/wildlife/weeds/pdf/cop_ragwort.pdf
www.knepp.co.uk
www.ragwortfacts.com/index.html
www.soilassociation.org/certification
If
you would like to see maps of where we will
be cutting margins please click here
for:-
Pondtail
and Knepp Park - Dial
Post and Swallows - Dragons
Green and Shipley
Countryman
and Hooklands Lane
For
more information, look
at this extract from Buglife’s
fascinating website
www.buglife.org.uk
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