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67
Proceedings of the X International Symposium on Biological Control of Weeds
4-14 July 1999, Montana State University, Bozeman, Montana, USA
Neal R. Spencer [ed.]. pp. 67-79 (2000)
Biological Control of Ragwort (Senecio jacobaea L.) in Australia
D. A. McLAREN1, J. E. IRESON2, and R. M. KWONG1
1CRC for Weed Management Systems and Department of Natural Resources and
Environment, Keith Turnbull Research Institute, Frankston, 3199, Victoria, Australia
2Tasmanian Institute of Agricultural Research,
13 St John’s Avenue, New Town, Tasmania, 7008, Australia
Abstract
The history of biological control of ragwort in Australia is outlined. Five biological
control species have been released in southern Australia since the 1930s but only 3 have
established. The flea beetle, Longitarsus flavicornis, has now dispersed over all ragwort
infested areas of southern Tasmania and 90% of infestations in northern Tasmania. In
some localities it has reduced ragwort densities by up to 95%. L. flavicornis has only
established in high altitude, high rainfall locations in Victoria from where it has spread
very slowly and has not had a significant impact. Longitarsus jacobaeae has established
in a few isolated locations in Tasmania and Victoria and is yet to have a significant impact.
The ragwort stem and crown boring moth, Cochylis atricapitana, is establishing in both
Victoria and Tasmania with recoveries at 35% and 67% of release sites respectively. At
one Victorian site it has dispersed more than 10 sq. km and is reducing the height of flow-
ering ragwort plants and killing smaller rosettes during autumn. Numerous attempts
between 1930 and 1983 to establish Northern Hemisphere biotypes of the cinnabar moth,
Tyria jacobaeae, have failed. Since 1995, attempts have been made to establish a New
Zealand biotype that is adapted to Southern Hemisphere conditions. Although recoveries
have been made from several sites there is still no evidence that it can be permanently
established in Australia. The ragwort plume moth, Platyptilia isodactyla, is currently
undergoing host specificity testing and, if specific, will be released during spring/summer
1999.
Keywords: Ragwort, Senecio jacobaea, biological control, Longitarsus flavicornis,
L. jacobaeae, Cochylis atricapitana, Botanophila seneciella, B. jacobaeae, Platyptilia
isodactyla.
Introduction
Ragwort, Senecio jacobaeae L. (Asteraceae), is a weed of major economic signifi-
cance that invades disturbed high rainfall areas of Australia, North America, Canada, New
Zealand, South Africa and Argentina. Ragwort has been accidentally introduced into these
countries from its native regions of Europe and Western Asia (Schmidl 1972). Biological
control programs are now being undertaken against ragwort in Australia (Field 1989),
New Zealand (Syrett 1983), North America (McEvoy et al. 1991) and Canada (Harris et
al. 1984).
Ragwort has been recognised as a serious weed in Australia since late last century
when it was first proclaimed under the Victorian Thistle Act 1890. It is found in the Otway,
Dandenong and Strzelecki ranges of southern Victoria and in high rainfall areas of south-
68 McLaren et al.
ern and northern Tasmania. Ragwort has detrimental effects on agricultural production but
can also affect natural ecosystems. It is an extremely invasive weed which can quickly
spread throughout a property, particularly dairying, beef or equine enterprises where cat-
tle and horses selectively avoid ragwort. In disturbed areas, ragwort seed will germinate
and compete with pasture plants, leading to a decline in pasture productivity (Poole and
Cairns 1940). The annual cost of ragwort to Australia has been conservatively estimated
at $4 million, including lost production to the dairy and beef industries and the costs of
control (McLaren and Mickan 1997).
Ragwort is not a serious weed in its native environment in Europe because it is kept
in check by more than sixty different insect and pathogen species. These do not occur nat-
urally in Australia (Schroeder 1978). Biological control of ragwort in Australia has been
underway since the 1930s with 6 different agents being introduced and 5 being released.
This paper outlines the history of these releases and describes the progress being made in
controlling this weed.
Materials and methods
To determine establishment of ragwort biocontrol agents in Victoria, 50 randomly
selected ragwort plants at the release site were searched for adults, larvae or signs of
attack. If attacked plants were found, checks of another 50 plants were undertaken at 50m,
100m, 200m, 300m and 1 km intervals from the release site until no attacked plants were
found. Assessments were made at the times of year favourable for detection of the agents.
Studies on the impact of C. atricapitana on ragwort growth and survival were under-
taken at an established release site at Callignee South, in the Strzelecki Ranges of
Gippsland, Victoria. In 1993, C. atricapiatana oviposition was observed on many ragwort
rosettes. Fifty of these were tagged on 18 March and their diameters were measured and
compared to fifty rosettes not colonized by C. atricapitana in the same locality. Plant sur-
vival and growth (live rosette diameter) were measured at 4 and 6 weeks after plants were
tagged. Similarly, in 1998, the heights of fifty flowering ragwort plants attacked by C. atr-
icapitana were compared to the heights of fifty unattacked flowering plants.
In Tasmania, establishment assessments for Longitarsus spp. were based on the recov-
ery of adults in vacuum samples using a Ryobi Scrub Hornet®vacuum machine fitted with
a lawn vacuum attachment. Sampling was conducted from early January to early March,
when populations of L. flavicornis were at or near maximum densities (Ireson et al. 1991).
A maximum of 5 vacuum samples was used to determine the presence of L. flavicornis
adults at any site. Approximate area of spread was determined using the Tasmap
1:100,000 series (Ireson et al. 2000).
L. flavicornis was considered to have “established” if the population had survived at
the site for at least 2 years and was reproducing and spreading outside the area of release.
L. flavicornis was classed as “surviving” at a site (but establishment uncertain) if it had
survived and reproduced at least 1 year after release (i.e. after 1 generation), but was only
located within the area of release. A third category was used for sites at which there were
no adult recoveries, suggesting failure to establish (Ireson et al. 2000)
Results and discussion
The status and effects of natural enemies imported and released in Australia for bio-
logical control of ragwort are shown in Table 1.
69
Cinnabar Moth, Tyria jacobaeae (L.) (Lepidoptera: Arctiidae)
Biological control of ragwort in Australia began when the Council for Scientific and
Industrial Research (CSIR) introduced the foliage feeding cinnabar moth, T. jacobaeae,
into Australia. It was first released in 1930 (Currie and Fyfe 1938). Several introductions
of T. jacobaeae were made between 1930 and 1982, none of which were successful
(Bornemissza 1966; Field 1989).
In 1993, T. jacobaeae was imported from New Zealand into Tasmania (Ireson 1998).
Progeny from this stock were used for mass rearing and annual field release in Tasmania
and Victoria between 1993 and 1998. During this period over 282,000 larvae and over
2,000 (range 300-500 per site) adults were released. The mean number of larvae released
per site in Tasmania was approximately 8,000 (range 1,000-42,500) (Ireson 1998).
In Victoria, the rearing and release program was largely undertaken via a network of
city and regional schools. The large brightly coloured larvae of T. jacobaeae provided an
excellent educational tool to help teach students about biological control and how it can
be integrated with conventional control methods. Schools were provided with the neces-
sary equipment to rear the insects (donations from local business and support from the
Dairy Research and Development Corporation) and the technical help to enable them to
successfully rear and release T. jacobaeae. As many the students came from farms with
ragwort infestations, this program has been invaluable in getting information on ragwort
control back to their communities.
In Tasmania, data from monitoring 36 release sites show an annual decline in the size
of field populations and the number of sites at which the agent was recovered (Ireson
1998). By January 1999, surviving colonies were found at only 4 (44%) of the 1 year old
sites and 1 (20%) of the 2 year old sites. No surviving colonies were found at 3-5 years
old sites. In Victoria, recoveries have been made from 5 out of 11 sites assessed with one
site surviving for 3 years.
Harris et al. (1971) reported that field establishment of T. jacobaeae in Canada fol-
lowed a pattern of high mortality of laboratory reared stock during the first year after
release and a stabilisation of the population for the following 2 years. A four to five fold
increase in population then occurred in the fourth and later years. Syrett et. al. (1991)
reported similar trends in New Zealand where establishment was recorded at 35% of the
release sites. In Oregon (USA), Isaacson (1973) found no significant increase in either T.
jacobaeae density or spread at any site until 5 years after the release. Similar trends are
not yet apparent in Australia where T. jacobaeae populations are going through steady
annual decline. The average size of larval populations released in Australia (8,000 or
more) is considerably higher than in Canada, the USA or New Zealand (1,000 or less)
where establishment has been achieved (Harris et al. 1975; Brown 1989; Syrett et al.
1991).
Numerous unsuccessful attempts at establishing T. jacobaeae in Victoria between
1930 and 1982 were attributed to disease, field predation and the importation of biotypes
from Europe that were ill adapted to the ragwort infested areas of Victoria (Bornemissza
1966; Schmidl, 1972, 1981; Field 1989). In particular, Bornemissza (1966) believed pre-
dation by the scorpion fly, Harpobittacus nigriceps (Selys) was the most serious factor
preventing establishment of T. jacobaeae. The 1993 introduction of a New Zealand bio-
type was thought advantageous as the population was synchronised with the southern
hemisphere and Harpobittacus spp. were uncommon in its primary location for release
(Tasmania). However, examination of other potential arthropod predators in Tasmania has
Biological control of Ragwort in Australia
70
identified carabid, staphylinid and cantharid beetles, mites, spiders, isopods (slaters), ants
and the European earwig, Forficula auricularia L. (Ireson 1998). These groups or species
have been recorded attacking either eggs, larvae and/or pupae of T. jacobaeae in overseas
studies (Wilkinson 1965; Dempster 1971,1982; Harris et al. 1975; Isaacson 1973; van der
Meijden 1979).
In Victoria, Bornemissa (1966) recorded T. jacobaeae pupae being parasitised by
unnamed tachinids and ichneumonids. No vertebrates have been observed attacking T.
jacobaeae in Australia during the current program of releases and monitoring. It is likely
that the combined effect of common arthropod predators and parasites may be a factor in
preventing establishment of T. jacobaeae in Australia.
Lakhani and Dempster (1981) identified food availability as the main factor deter-
mining T. jacobaeae abundance. As food supply is not limiting in Australia and large
release numbers were used to attempt to overcome predation, it is possible that climatic
factors or plant nutritional factors are limiting establishment. Many areas infested with
ragwort in Australia are prone to waterlogging during winter. Waterlogging has been
shown to be detrimental to the survival of over-wintering pupae of T. jacobaeae
(Dempster 1971).
Ragwort seed flies, Botanophila seneciella (Meade) and B. jacobaeae (Hardy)
(Diptera: Anthomiidae).
The ragwort seed fly, Botanophila seneciella, (formally Pegohylemia) was first intro-
duced into Australia in the 1930s from England and New Zealand (Delfosse and Cullen
1982) but due to disease and difficulties in rearing none were released. A further intro-
duction, believed at the time to be Botanophila seneciella (referred to as Hylemia
seneciella), was made in 1958 but was later identified from voucher specimens as
Botanophila jacobaeae Waterhouse (Hoy 1958). These were released in both Victoria and
Tasmania (Hoy 1958, 1960; Schmidl 1981; Field 1989). None of the species have estab-
lished in Australia (Table 1).
Ragwort flea beetles, Longitarsus flavicornis (Stephens) and L. jacobaeae
(Waterhouse) (Coleoptera: Chrysomelidae).
A species initially identified as Longitarsus jacobaeae was introduced to Australia
McLaren et al.
Table 1.
Natural Enemies imported and/or released in Australia for biological control of
ragwort (adapted from Delfosse and Cullen 1982)
Biological Control Country of Origin Date Date Status Effect
Agent Imported Released on Plant
Tyria jacobaeae England via 1929-32 1930-32 NE -
(L.) New Zealand
England 1934-37 1935-38 NE -
England 1955, 1957 1955-62 NE -
Italy 1955 1955-56 NE -
England 1959 1956-60 NE -
Switzerland and Austria 1961-62 1962-64 NE -
71
from Annonay, France in 1977 and released in 1979. It was later identified as the taxo-
nomically similar species, Longitarsus flavicornis (Field et al. 1988). At some localised
sites in Victoria L. flavicornis has controlled ragwort infestations (McLaren and Micken,
1997) but to date has not established widely and has yet to impact greatly on ragwort
infestations. In 1984, seven populations of L. flavicornis were introduced into Australia
from Spanish locations thought to climatically match ragwort infested areas in Australia.
Though initial recoveries were promising (Field et al, 1988) establishment of these new
biotypes have also failed to effectively control ragwort in Victoria. In total, only 10 out of
127 L. flavicornis releases (most releases exceeded 1000 adult beetles) have established
and these have all been in high altitude high rainfall localities of Victoria. However, bio-
Biological control of Ragwort in Australia
Biological Control Country of Origin Date Date Status Effect
Agent Imported Released on Plant
Switzerland and Sweden 1977 1978 NE -
via Canada
Switzerland 1978 1979 NE -
Ex France via U.S.A 1993 1993-99 SU TE
via New Zealand
Botanophila England 1934, 1936 NR - -
seneciella (Meade)
Botanophila England via 1933 NR -
jacobaeae New Zealand
Waterhouse
England via 1959 1959 NE -
New Zealand
Longitarsus France 1977 1979-1999 E, A - Tas S - Tas
flavicornis E, S - Vic N - Vic
(Stephens) Spain 1984 1985-90 E, R N
Longitarsus Italy via Oregon USA 1988 1988-91 E, R N to S
jacobaeae via New Zealand locally
(Waterhouse)
Cochylis Spain 1985 1987-98 E, A L
atricapitana
(Stephens)
Platyptilia Spain 1995 NYR - -
isodactyla
(Zeller)
Status Effect on Plant
NYR = Not yet released, but release expected or possible N = Negligible
NR = Not released L = Light
E, A = Established and abundant S = Significant
E, R = Established, rare TE = Too early to judge
E, S = Established, scattered and localised Tas = Tasmania
NE = Not established Vic = Victoria
SU = Scattered, establishment uncertain
72
logical control agents are capable of adapting quickly to new environments (Myers 1976)
and in time it would be expected that L. flavicornis will adapt to attack ragwort in
Victorian locations where it hasn’t established to date.
Tasmanian studies on the biology and efficacy of the French biotype of L. flavicornis
were carried out at two established sites (Lachlan in the south and Mayberry in the north)
from 1985 to 1989 (Ireson et al. 1991). L. flavicornis was released at both sites in 1979
and by May 1989 (approximately 9 years after its release) had reduced ragwort densities
by as much as 90%. High densities of the French biotype of L. flavicornis, and corre-
sponding reductions in ragwort densities, have occurred over the same time scale record-
ed by Ireson et al. (1991) in all the major ragwort infested regions of the state (Ireson
1993; Ireson 1995). A successful redistribution program has accelerated population dis-
persal (Ireson et al. 2000). This has involved the field collection and transfer of almost 2
million adults to 875 new sites. About 88% of the transfers took place between 1993 and
1999 (Ireson et al. 2000). By February 1999, it was estimated that the French biotype of
L. flavicornis had spread throughout all ragwort infestations in southern Tasmania and
about 90% of the major infestations in northern Tasmania (Ireson et al. 2000).
On many dairy farms in northern Tasmanian, the impact of L. flavicornis is being
restricted, possibly as a result of unfavourable site conditions and incompatible manage-
ment practices. It is suspected that the pugging of wet ground by cattle is causing high lar-
val mortality at some sites (Ireson et al. 2000) and use of boom sprayed herbicides may
also be a limiting factor (Boersma 1996). Integrated management strategies are now being
developed that will utilise chemical and mechanical control methods and grazing strate-
gies that promote the survival of L. flavicornis (Ireson 1998).
An Italian biotype of L. jacobaeae was introduced and released in 1988. L. jacobaeae
adults can aestivate in summer, and survive in localities experiencing dry summer cli-
mates (Frick and Johnson 1973). This species has successfully controlled ragwort along
the Pacific northwest coast of the United States and was thought to be an appropriate
species for drier, low altitude sites in Victoria where L. flavicornis had previously failed
to establish. In Victoria L. jacobaeae was released at 17 and established at 3 sites between
1988 and 1990. L. jacobaeae has reduced ragwort density by 95% at one of these sites
(McLaren and Mickan 1997) but its spread and overall impact has been minimal to date.
In Tasmania, L. jacobaeae was released at 26 sites between 1988 and 1990. Surveys
have indicated that it has only survived at 5 sites in northern Tasmania (Ireson 1998).
Ragwort Stem and Crown Boring Moth, Cochylis atricapitana (Stephens)
(Lepidoptera: Cochylidae).
The ragwort stem and crown boring moth, C. atricapitana was introduced into
Australia from Salamanca, Spain in 1985 and released in Victoria in 1987 (McLaren
1992). C. atricapitana larvae bore into the crowns and stems of ragwort plants from
spring through to autumn and may have 2 or 3 generations in a season (McLaren 1992).
By 1992, C. atricapitana had established at only 2 of the 25 sites (8%) assessed in Victoria
(McLaren 1992) but by 1999 it had established at 28 out of 129 sites (22%) (Table 2). At
one site, C. atricapitana has spread over an area of more than 10 km2. In Victoria, it has
taken C. atricapitana 11 years to build up to a population size where it is now dispersing
and exerting some impacts on ragwort size and growth. In 1998 (ten years after release),
a comparison of the heights of attacked and unattacked flowering ragwort showed that C.
atricapitana was stunting growth and reducing ragworts height (Figure 1). Similarly, at
McLaren et al.
73Biological control of Ragwort in Australia
Table 2.
Establishment and dispersal of C. atricapitana in Victoria to February 1998
Period after release (Years) 123456-12 Total
No. sites assessed 9 30 32 6 12 39 129
Agent not recovered 7 22 22 1 7 25 84
Agent only at site 26614 5 24
Agent at least 50m from site 1 2 3 2 8
Agent at least 100m from site 1 2 2 5
Agent at least 200m from site 1 1
Agent at least 300m from site 1 2 3
Agent more than 1 km from site 4 3
Sites where agent surviving* 2 8 10 5 5 15 45 (355%)
Sites where agent established** 0125 5 1528 (222%)
# Does not include destroyed sites (e.geg. spraying, over grazing, fire, etc).
* Sites where C. atricapitana is surviving are those where it has been found
within100 m of the release site 6 months to 2 years after release.
** Established sites are those where C. atricapitana have survived for 3 or more years
or are increasing their population and have spread at least 100 m from the release
site after two years.
0
100
200
300
400
500
600
700
800
900
1000
Attacked by C. atricapitana Control
Ragwort Height (mm)
Figure 1. Impact of Cochylis atricapitana on the heights of flowering ragwort plants
at Callignee South, Gippsland, Victoria.
74 McLaren et al.
Table 3.
Establishment and dispersal of C. atricapitana in Tasmania to February 1999
Period after release (years) 6 months 1 2 3 Total
No. sites assessed 4 13 6 4 27
Agent not recovered 0720 9
Agent only at site 4311 9
Agent at least 50m from site 2 2 4
Agent at least 100m from site 1 1 2
Agent at least 200m from site 3 3
Sites where agent surviving* 464418 (67%)
Sites where agent established** 0 0 1 34 45 (15%)
* Sites where C. atricapitana is surviving are those where it has been found within
100 m of the release site 6 months to 2 years after release. It also includes
established sites.
**Established sites are those where C. atricapitana have survived for 3 or more years
or are increasing their population and have spread at least 100 m from the release
site after two years.
0
20
40
60
80
100
120
18/03/93 14/04/93 28/04/93
Date Assessed
% Rosette Survival
0
50
100
150
200
250
Rosette Daimeter (mm)
Control Survival
Cochylis Survival
Rosette Diameter - Cochylis
Rosette Diameter - Cont rol
Figure 2. Impact of Cochylis atricapitana on rosette survival and growth between 18/3/93 and
20/4/93 at Callignee South, Gippsland, Victoria.
75
the same site in autumn 1993, a comparison of ragwort rosettes attacked by C. atricapi-
tana to unattacked rosettes showed that larvae were killing rosettes and reducing the
diameter of live rosette tissues. (Figure 2).
Parasites and predators could be affecting establishment of C. atricapitana at some
sites in Victoria. An unidentified tachinid (Diptera) was found parasitising a larva while
spiders and birds such as the grey fantail, Rhipidura fuliginosa (Sparrman),have been
observed eating adult moths. The superb fairy wren, Malurus cyaneus (Latham) has been
observed flying from one flowering ragwort to another, gleaning insect prey which could
include C. atricapitana.
C. atricapitana was introduced into Tasmania in 1994. The first field release com-
menced in 1995 and by September 1998 the agent had been released at 27 sites (Ireson
1998). Results of establishment assessments at these sites to February 1999 show that C.
atricapitana had established at 5 out of 27 sites assessed (15%) but is surviving (but estab-
lishment uncertain) at 67% of sites (Table 3). The maximum distance dispersed (200 m in
3 years) is greater than at sites in Victoria where the maximum recorded dispersal in 3
years has been 100 m (McLaren, 1992). This suggests that the agent has the potential to
spread more rapidly in Tasmania.
The ragwort plume moth, Platyptilia isodactyla (Zeller) (Lepidoptera:
Pterophoridae)
Platyptilia isodactyla was selected as a potential biological control agent because it
caused substantial damage to ragwort plants (Vayssieres and Rahola 1985) and would
only feed on a few plant species within the Tribe Senecionae (Cullen et al. 1985). P. iso-
dactyla is currently undergoing host specificity testing at the Keith Turnbull Research
Institute by the Victorian Department of Natural Resources and Environment. This agent
was collected from the province of Lugo in central to northern Spain but has also been
recorded in southern Spain (Gielis 1988) and the British Isles (Emmet and Heath 1989).
Its most common host is marsh ragwort, Senecio aquaticus Hill (Emmet and Heath 1989),
which is taxonomically very similar to ragwort. Marsh ragwort and ragwort will hybridize
producing plants exhibiting intermediate characters and hybrids are apparently fertile
(Turtin et al. 1976).
Adults fly in spring and autumn (Emmet and Heath 1989) and lay eggs mainly on the
underside of leaves. An average of 100 eggs are laid per female which take 12 days to
hatch at 20°C (Masri 1995). Larvae tunnel down into the crown of rosettes or into the
stems of flowering plants where they pass through five larval instars. The larvae pupate
either inside the plant, within curled ragwort leaves or in the soil surrounding the plant
(Masri 1995). Larvae cause considerable damage with only two or three larvae being
capable of killing a small ragwort rosette.
Host specificity testing of P. isodactyla suggests that this species is unlikely to com-
plete its development on plant species outside the Tribe Senecionaeae. A total of 72
species have been tested according to the centrifugal phylogenetic protocols outlined by
Wapshere (1975) with complete development occurring on 7 species. Of these, all were
within the Senecionaeae tribe except for aster, Callistephus chin, where one adult emerged
(0.5%) but was deformed and died within a few hours. In all cases survival on plant
species was minimal (less than 6%) compared to ragwort (greater than 45%). Additional
host specificity testing is being undertaken to confirm these observations.
Biological control of Ragwort in Australia
76
Conclusion
Classical biological control using, L. jacobaeae (Italian biotype), T. jacobaeae and B.
seneciella has been used successfully to control ragwort in western Oregon (USA)
(McEvoy et al. 1991). Coombs et al. 1996 reports that this has resulted in annual savings
of $5 million from reduced livestock losses, herbicide use and increased pasture produc-
tion. In Tasmania, control of ragwort with L. flavicornis has already been achieved at
many sites. The number of infestations controlled should increase rapidly now that the
species has become widespread and has been recorded in high densities in all the main
ragwort infested areas of the state (Ireson et al. 2000). It is expected that C. atricapitana
and perhaps P. isodactyla (if released) will augment the impact of L. flavicornis in
Tasmania. These species will be particularly useful if they can survive well in areas where
L. flavicornis has failed to have a significant impact.
L. flavicornis has not been as successful in Victoria and perhaps its survival in high
altitude, high rainfall locations is equivalent to a 3 to 6 degree shift south in latitude to
Tasmania, where the species has performed well. Results obtained with C. atricapitana
(Figs. 1 and 2) now look promising. At some sites, C. atricapitana moths are dispersing
over considerable distances and a recent mass rearing program has produced 152 new
releases (McLaren 1999). It is anticipated that within the next 1-2 decades, most Victorian
ragwort infestations will be colonized by C. atricapitana.
It has been shown that the combined impact of two or more insects feeding on differ-
ent plant parts and at different times of the year can have a greater impact than either
insect acting alone (James et al. (1992); McEvoy et al. (1991)). It is anticipated that the
combined actions of L. flavicornis, L. jacobaeae, C. atricapitana, T. jacobaeae and P. iso-
dactyla (if released) in conjunction with changes in ragwort and grazing management, will
have significant impacts on reducing ragwort infestations in Australia in the coming
decade.
Acknowledgements
We are grateful to Karen Green and John Stoner (Keith Turnbull Research Institute),
Richard Holloway, Wade Chatterton and Wal Ashby (Tasmanian Institute of Agricultural
Research), and Sandy Leighton (Meander Valley Weed Strategy, Tasmania) for technical
assistance. We also thank Ian Faithfull for reviewing the manuscript. Funding support for
the program has been gratefully received from the Dairy Research and Development
Corporation and the Natural Heritage Trust.
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