 Conference
1999
New Zealand Plants and their Story
Pest
Plants and their Control
Kevin
Worsley
Biosecurity Department
Wellington Regional Council
The Early Years
Since the first European
settlements in New Zealand there has been a continuing influx of
alien plants. From 1789 when the first adventive plant was recorded
to today an estimated 25000 plant species have by various methods
found their way into this country. Most were and continue to be
intentional introductions brought in for a range of reasons with
the most common economic. Over 80% are plants of urban gardens but
over time many have escaped to become weeds of natural habitats
and agricultural land. Today an estimated 2000 intentional and accidental
introductions are considered weeds.
Where Europeans in particular
have colonised new lands throughout the world the translocation
of species for economic, aesthetic or cultural reasons always occurs.
This was never more so than during the early years of New Zealand
settlement where as a country of agricultural potential, introductions
mainly involved species then considered important to that industry.
European grasses and cropping seed were the earliest imports, unfortunately
often contaminated with a range of already recognised pasture weeds
such as thistles and ragwort.
Settlers desire to brighten
up areas cleared of what was to them the drab New Zealand bush introduced
more colourful flowering shrubs which included soon to become weeds
such as gorse, broom, hawthorn and brier. Often these species were
planted as a reminder of the Old Country, as live fences, for stock
shelter or fodder.
Gorse is one of the most
recognised agricultural weeds in New Zealand. Introduced from Western
Europe in the very early stages of European settlement it was recorded
by Charles Darwin during his voyage through New Zealand waters in
1835 as growing in hedges in the Bay of Islands. It's spread and
development as a weed in this country's temperate climate was rapid
but settlers failed to recognise the threat, and gorse seed continued
to be imported and plantings deliberately established into the 1900's.
The Start of Legal Control
In 1859 in what was one
of the earliest legal enactment's requiring the control of a plant
species, the provincial Governments of Taranaki and Nelson passed
laws compelling farmers to keep gorse hedges trimmed and banned
the planting of new hedges. However, in 1860 a gorse nursery established
at Wanganui was reported to be selling gorse plants for one shilling
each. A similar enterprise is recorded as operating at Featherston
in the Southern Wairarapa. This latter venture is the probable source
of what was to become major infestations through the Rimutaka road
and rail routes and further south into the Wellington area.
Let me use my home area
of the Wairarapa as an example of how humans intentionally spread
what was to become New Zealand's most costly weed to control. At
Stronvar north east of Masterton in the 1880's on what was then
a very large sheep station, gorse was sown with the seedling material
used to fatten lambs. At Mangapakeha at about the same time, gorse
established as a result of an English settlers desire to have a
reminder of home, namely a gorse hedge around his cottage. Gorse
was also sown to stabilise embankments formed during railway construction
through the Mauriceville area north of Masterton. From each of these
sites large spreading infestations over hundreds of hectares resulted,
peaking in the late 1940's and costing past, present and future
generations a great deal to clear and control. I would suggest this
example is typical of a range of weeds currently affecting agriculture
in many parts of New Zealand, as are the methods of introduction.
Other Provincial legislation
was being enacted at about the end of the 1880's, for example the
Otago Provincial Councils' requirement to clear Californian Thistle.
This species had spread through much of the Province and there was
a fear that it would over take all pastureland. One can only wonder
at what control methods were attempted in those days considering
the difficulty to clear this species even with today's technology.
National Legislation
for Weeds
The first national legislation
requiring the control of problem weeds was the 1900 Noxious Weeds
Act, followed by the 1928 Act which continued through with some
amendments until 1950. Both were administered by the Department
of Agriculture. Following the 1928 Act a local authority could if
it so decided, take over this responsibility, but generally few
did.
These were years prior
to the advent of true herbicides and periods of major world upheavals
such as the World Wars and the Great Depression so the spread of
the mainly agricultural noxious weeds continued fairly much unabated
even with the best efforts of man.
Major Changes
Following the introduction
of the 1950 Noxious Weeds Act, real control progress began. This
Act gave administrative responsibility to County Councils and although
not compulsory, government subsidies made it attractive enough for
most to become involved. This coincided with a period of extraordinarily
high returns for New Zealand farmers which when coupled with the
introduction into New Zealand of the first selective herbicides
namely 2,4-D and 2,4,5-T saw the beginning of real progress in sustainable
noxious weed control.
The 1950 Act had two
major deficiencies; one it was not compulsory for local bodies including
town and city councils to assume administrative responsibilities,
and two the Crown was not bound and could and often did ignore requests
by administering authorities to clear its own land.
These situations often
caused heated debate particularly by neighbouring landowners who
were required to clear noxious weeds only to look over the boundary
into a rail or other government reserve or drive into a town area
and note the unabated spread of the same species.
The Subsidy Years
In the late 1960's Britain
joined the EEC beginning a decline in the export value of many of
our agricultural products. To boost production the New Zealand Government
introduced a range of agricultural subsidies with one giving a 47%
rebate on the purchase of herbicides. Use and type was not specified
and a proportion of this subsidy helped to control weeds on sports
grounds, home gardens and on a range of other non-productive areas.
In 1973 the Kirk Labour
Government in its first budget announced a new subsidy covering
50% of the total cost of clearing specific noxious weeds.
This subsidy allowed
payments through MAF of 50% of the cost of chemical and application
for initial clearance and ongoing control of up to three inputs
on any site when approved by the local weed authority. Approved
mechanical clearance such as root-raking was also subject to subsidy.
The eligible species
were the then main noxious pasture weeds in New Zealand and with
slight variation between the MAF regions included gorse, blackberry,
broom, ragwort, nodding thistle and variegated thistle.
The Land Development
Encouragement Loan Scheme opened up large areas of scrub for pasture
production. Under the scheme, loans for approved work were arranged
by the Rural Bank and so long as the farmer cleared and maintained
the area involved for a determined period of time, the loan was
written off.
While in most instances
sustained production was achieved, in others the total exercise
was a disaster with large areas of steep native scrubland cleared
only to erode or revert to weeds such as broom, gorse or tauhinu.
Other production incentives
were introduced by Governments over following years, all with the
aim of clearing more land or gaining increased productivity off
existing pasture.
The 1978 Noxious Plants
Act
During this subsidy period
weed legislation was again reviewed and in 1978 the Noxious Plants
Act became law. This required the establishment of a Noxious Plants
Council with responsibility to approve the formation of District
Noxious Plants Authorities (DNPA's), oversee a range of subsidy
issues determined by the Minister of Agriculture, review and approve
the classification of noxious plants, and determine and implement
a training programme for noxious plants officers.
The Crown was at last
bound and like any other land occupier was required under threat
of prosecution to comply with the act.
DNPA's were a significant
innovation over the 1950 Act in terms of local administration. All
local authorities including urban either singularly or in groupings
were required to form an independent authority with the sole purpose
of noxious plants administration.
Each authority employed
one or more officers, approved subsidised noxious plant control
programmes and recommended to the NPC the classification of plants
in their district. Membership of the 80 DNPA's spread throughout
the country covered a range of land use interests and in some instances
an environmental influence was becoming evident.
The plants control subsidy
period ended in 1985 when with most other agricultural assistance
schemes it was discontinued in the early days of Rogernomics. This
resulted in what could be considered an intense initial period of
reversion when with low commodity prices and no financial assistance
many farmers were forced to close the gate on many of their marginal
blocks.
With a degree of hindsight
a high proportion of the areas developed under subsidy, particularly
the Land Development Encouragement Scheme, should never have been
cleared in the first place.
However in my experience
most farmers made every effort to maintain their better land under
what were very difficult conditions during the late 1980's and have
generally continued to do so to the present time.
Regional Councils
Local Government reform
and the establishment of regional councils in late 1989 saw the
demise of DNPA's. Their responsibility for noxious plant control
was taken over and became one of the many functions of the 13 regional
councils and one unitary authority covering New Zealand.
Regional Councils by
their nature and their involvement as the major administrators of
the RMA are very much concerned with environmental matters and this
began to be reflected particularly in the northern regions with
greater attention being given to species affecting the environment
rather than agriculture.
Declining emphasis on
certain pastoral noxious plants also reflected the continuing poor
returns many in that industry continued to experience.
Biosecurity Act
In October 1993 the Biosecurity
Act came into force. This legislation introduced as an Act to restate
and reform the law relating to the exclusion, eradication and effective
management of pests and unwanted organisms would eventually replace
some 28 enactment's including the Noxious Plants Act and the Agricultural
Pests Destruction Act, both administered by regional councils.
Under this new legislation
a five-year strategy for pest plants was developed by each participating
regional council through a public consultative process. Following
approval and implementation of a pest plant strategy the requirements
of the Noxious Plants Act ceased to apply in that region.
Under the Biosecurity
Act a regional council is not required to develop a strategy. However
with the exception of the West Coast all have.
Like a number of other
councils, Wellington Regional Council commenced its Pest Plant Management
Strategy in July 1996 with a five-year life to July 2001. In keeping
with the tenor of the Act the species listed and control requirements
in the WRC Strategy are more focused on invasive environmental plants
with the aim of protecting a range of environmentally sensitive
risk areas.
Plants listed are mainly
garden escapes and as such are prevalent in urban situations. The
eight plants officers employed by the WRC would spend roughly 80%
of their time on inspections and other related activities in urban
and reserve areas with Wellington City receiving the most attention.
The Current Situation
The responsibility to
clear and control pest plants lies with the landowner or occupier.
This has been the case under all the previous legislation.
Plants officers must
therefore by whatever means coerce people into clearing plants that
many will consider not to be causing a problem. Often some pest
plant species are considered attractive or a garden feature but
more often co-operation is difficult to gain because of the effort
required to clear an infestation or the cost.
WRC has an annual
budget of $37,000 as expenditure on Pest Plant promotions.
In an effort to get the message on pest plant control out to the
general public a range of activities are implemented including:
- Involvement with
displays at major garden, horticulture, and A&P shows.
- Small, unattended
displays at various venues including, shopping malls and libraries.
- Talks and plant displays
at schools.
- Regular articles
in community newspapers.
- Publishing and updating
of pamphlets and diagrammatic control information sheets.
- Talks to a wide range
of interest groups.
Wellington City Eradication
Programme
In 1989 when the WRC
was established, Old Mans Beard (OMB) was not classified as a noxious
plant in Wellington City. At that time the infestation levels were
considered to be at a level where control was impractical.
As much of the infestation
was on Wellington City Council (WCC) reserve a co-operative control
programme was negotiated between the two councils whereby WCC would
commence a progressive clearance scheme on its land particularly
road reserve and WRC would ensure control on private land. A case
was presented to the Noxious Plants Council and in 1991 the species
was classified.
Both parties started
control work soon after in the northern suburbs and a total clearance
programme has continued south. WRC now employs 3.5 full time staff
on the Wellington programme whose main function is to systematically
inspect every property in the survey area and ensure all infestations
are cleared. Since the implementation of the Regional Pest Plant
Management Strategy other species have been included in the control
programme. These are Wild Ginger and Cathedral Bells with both proving
to be common through the City.
Enforcement
To obtain total control
a firm line is taken. Where a site of one or more of the species
is located, ownership of the property is established and the owner
notified in writing and requested to clear the infestation. Generally
28 days is given for this to be completed. Where the site is small,
with the written agreement of the owner that herbicide may be applied,
a plants officer will clear the infestation as a customer service.
After 28 days the site is re-inspected and if the work is not completed
a Notice Of Direction is issued. Generally another 28 days is given
and if on inspection a satisfactory level of control has not been
achieved the owner is advised that a contractor will be directed
to enter the property and carry out the work at the owners expense.
Following normal invoicing procedures if payment is not received
the cost of the exercise is placed as a Statutory Land Charge.
Pest Plants are not often
the problem. As I have stated earlier, it is people who first of
all introduce problem species either into New Zealand or into an
area. Then by various ways they will spread them further. Over the
last 18 months we have found garden shops selling Old Mans Beard
plants, dried Wild Ginger flowers and noted in the August edition
of a well known gardening magazine an advertisement seeking to purchase
seed or plants of Cathedral Bells.
People in this country
have an amazing interest in plants and their environment. Most recognise
the damage some species pose to that environment yet often these
same people carry on unaware of the possible damage their actions
can cause. We have found on a number of occasions dumps of garden
refuge on roadsides, riverbanks and in reserve areas
containing a variety of plant species including invasive pest plants
such as Old Mans Beard, Wild Ginger and Banana Passionfruit.
On a recent inspection
of a large DOC bush reserve adjacent to an urban centre, a little
over half an hours drive north of here, I noted along the boundary
with a number of rather expensive homes (each with manicured gardens)
piles of plant material dumped over the fence into the reserve.
A casual observation revealed Tradescantia and Japanese Honeysuckle
plus a host of other but less invasive species.
Along the coastal sand
dunes of this same centre a recent inspection revealed that almost
every beachfront property had a dump of garden refuge over the fence
or further out in the dunes.
The Future
As enforcement agencies,
regional councils can only handle a limited number of plant species
if reasonable control levels are to be achieved. Some councils have
introduced service delivery where the work is carried out on behalf
and at no cost to the land occupier. This generally involves only
a few key species of limited distribution and with the potential
to have major deleterious impacts.
Service delivery on pest
plants of limited distribution can be cost effective as control
is achieved at inspection, the work is carried out by an experienced
person and limited re-inspections are required.
WRC offers a limited
service delivery on minor sites of Wild Ginger and Old Mans Beard.
This offer is determined by the inspecting officer and work can
only proceed with the agreement of the occupier. However we do arrange
and fund clearance programmes on a few potentially hazardous species
of very limited distribution even though in some cases the sites
involved may be of a reasonable size.
Sweet Pea Shrub, Moth
Plant and Manchurian Wild Rice are recent examples.
Under the current WRC
Pest Plant Management Strategy control requirements are the responsibility
of the occupier and are species driven. It is possible that in the
next Strategy this may be modified to include full service delivery
on a few key species. A decision on which species and to what degree,
will be influenced by our current Surveillance Plant monitoring
programme. Zoning for service delivery will also be considered.
The other possibility
is plant control on a site basis. This could be in co-operation
with the Animal Pest programme where KNE (Key Native Ecosystem)
sites would be evaluated to include not only animal pests but also
pest plant damage. Where appropriate, key invasive plants would
be controlled both within a site and along a buffer zone on its
periphery.
As pest plant control
on any site to the point of complete eradication is a continuous
process over a long time, a KNE programme for weeds will on many
sites be more costly and prolonged than animal control. This would
limit the number sites that could be targeted if such a scheme is
implemented.
In well-established bush
reserves, only a few weed species are tolerant of low light conditions
and therefore invasive, however with more open regenerating areas
the range is far greater.
KNE sites also include
some wetland and dune areas. Both have their own particular weed
problems which in many case will be more difficult to deal with
then bush reserve.
In the end it is public
demand that decides everything. More and more of that demand is
growing for the protection and restoration of our natural areas.
Pest plant control is
just one facet in this restorative process and regional councils
are increasingly recognising their responsibility in this regard.
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