Chapter Two - A citrus canker outbreak in Emerald, Queensland
What is citrus canker?
2.1
Citrus canker is a highly contagious plant disease
caused by the bacterium Xanthomonas
axonopodis pv. citri. Citrus canker affects plants in the Rutaceae family,
including those from the genera Citrus, Fortunella and Poncirus.[4]
Strains
2.2
There are a number of distinct types of citrus canker
disease caused by various pathovars and variants of the bacterium. The Asiatic
variety of citrus canker (Canker A), is caused by a group of strains originally
found in Asia and is the most widespread and severe form
of the disease. While grapefruit, lime and trifoliate orange stock are
particularly susceptible to Canker A, it also affects most other varieties of
citrus, including mandarin, tangerine, satsuma and kumquat. Minor genetic variations of citrus canker
strains have been detected in the A strains in Florida
and other citrus growing regions of the world.
2.3
The canker most commonly called Cancrosis
B is caused by a group of strains originally
found in South America. This canker affects lemons,
Mexican lime, sour orange, and pummelo and is easily distinguished from strains
of the Canker A group.
2.4
A strain referred to as Cancrosis
C has also been isolated, after being found
in Mexican lime in Brazil.
The only other known host for this particular bacterium is sour orange and
strains of this particular group are not easily differentiated from the Cancrosis
B group.
2.5
A fourth group of strains, known as A*, has been found
in Oman, Saudi
Arabia, Iran
and India. This
group, which is limited in host range to Mexican lime, appears to be quite
distinct from the common A strains.
2.6
In 1981 there were reports of an additional strain –
also found to affect Mexican limes, in Mexico
– named Canker D. However, the official identification of this particular
strain remains controversial.
2.7
The symptoms of the various strains are generally
similar, and a specific strain may only be distinguished by scientific testing.
Symptoms
2.8
Citrus canker has characteristic symptoms which can
appear on the leaves, stems and fruit of an infected plant. Typically, small
yellow marks (approximately the size of pin heads) appear on the leaves. These
develop into small, pimply, watery spots which become more spongy and scab-like
over time and progress from white to tan as they grow.
2.9
Young lesions
appear raised on both leaf surfaces, but are usually more apparent on the lower
surface. As the lesions age and thicken, they become corky and often develop a
brown, crater-like depression in the centre. The edges of the lesions are
frequently watery and yellow-brown in appearance, fading to green, with a
surrounding yellow ring or halo.
2.10
Following leaf infection, the symptoms typically spread
onto stems, and eventually to branches. Cankers can occur on woody stems, the bark
may develop discoloured areas, and dieback of stems coupled with internal
reddening can occur. Ripening fruit on infected trees are also targets for
infection and affected fruit may develop scabs or pitting.
2.11
In the initial stages of the disease, lesions on the
rind of fruit often resemble large oil glands. These lesions then gradually
darken and become scab-like or cork-like in texture. Typically, lesions are
round, and occur either singly or in groups.
2.12
Canker lesions can vary in size between 5-10mm
depending on host susceptibility and the number of infection cycles. When
conditions are dry, lesions remain corky or spongy in appearance. When exposed
to wet conditions, however, lesions can expand rapidly, and take on a flatter,
water-soaked appearance.
2.13
Historically, citrus canker has had a serious impact on
local citrus industries whenever infections have been detected. A serious
citrus canker infection can cause defoliation, dieback, and premature fruit
drop. The disease can also retard the growth of young trees and set back
maturity for several years. Most significantly, the leaf, stem and fruit
blemishing directly reduces both the quantity and quality of fruit, and leads
to infected fruit becoming less valuable or completely unmarketable.
Life cycle and means of transmission
2.14
New outbreaks of citrus canker usually occur when new
shoots are emerging or when fruit are at an early stage of development. Canker
bacteria can enter through a plant's stomatal openings (the pores in the
surface of leaves through which air normally enters the leaves), or through
natural openings and wounds. A plant's susceptibility to infection can decline
with maturity and the first ninety days after petal fall are the most critical
for fruit infection.
2.15
Later infection results in the formation of small and
inconspicuous pustules only. Latent infections can occur on shoots infected in
autumn just before dormancy, with over-wintering bacteria forming lesions the
following spring.
2.16
The citrus canker bacterium can survive for up to ten
months in lesions on citrus. The bacterium can also survive for long periods in
diseased plant tissue (including discoloured bark tissue on tree trunks and
limbs) in plant debris, as an epiphyte[5]
on host and non-host plants, as a weak saprophyte[6], on straw mulch or in soil. The
viability of the bacteria decreases rapidly with exposure to sunlight or with
contact with soil micro-organisms. The bacterium does not survive well on the
surface of citrus leaves or in buried leaf litter. Dry, diseased leaves can,
however, harbour the bacteria for two to three months.
2.17
Over-wintering lesions, especially those formed on
angular shoots, are the most important source of inoculum for the following
season. During spring rains, dormant bacteria within the cankers multiply, ooze
out of lesions, and spread to new shoots and leaves and, when aided by wind and
rain, can spread to other plants in the area.
2.18
There is a higher risk of fresh infections from
over-wintered lesions in leaf or stem tissues where the initial infection
occurred in autumn. Because infections initiated in autumn are the freshest
before entering winter, they will carry a higher bacterial load than lesions
formed in summer, for instance. Similarly, bacterial levels in susceptible host
plants will be higher than in a tolerant variety. However, bacterium is able to
survive in low levels through winter in the lesions formed the previous spring,
provided conditions are mild.
2.19
Infection of young leaves in late autumn, prior to the
plant entering dormancy, can occur without the development of symptoms. As
environmental conditions become more favourable, bacterial populations
increase, canker lesions are formed and a new infection cycle can commence.
2.20
The most destructive phase of the disease tends to be
after heavy rains, (particularly during spring) and when the average
temperature is greater than 20 degrees centigrade. Dispersal of the citrus
canker bacterium within a tree canopy is aided by free moisture. Over short
distances, wind-driven rain, air currents, insects, birds and human movement
can spread the canker pathogen. Overhead or spray irrigation can escalate the
rate of disease spread in an orchard.
2.21
Over longer distances, dispersal is most common when
infected plant material is moved between areas. This includes bud wood,
rootstock, seedlings and budded trees, but less commonly fruit or leaves.
Movement of straw or mulch, contaminated clothing, tools, harvest and
post-harvest equipment are also potential sources of infection. However, the
bacteria responsible for citrus canker is able to survive on inanimate objects
for less than 72 hours, which means that if the contaminated item immediately
comes into contact with host plant material, there is an increased risk of
spreading the disease.
Prevalence of citrus canker
2.22
Citrus canker is not an endemic bacterial disease in Australia,
however it has had a serious impact on citrus industries in other parts of the
world.
2.23
Citrus canker is believed to have originated in areas
of South-east Asia and India,
and has since spread to most parts of the world. It is common in many tropical
and subtropical citrus growing areas of the world including Japan, some parts
of west and central Africa, the Middle East, southern Asia (including
Indonesia), the Pacific Islands (including Papua New Guinea), some areas of
South America and Florida in the United States.
2.24
The disease is
particularly widespread in China,
Japan, Malaysia
and Vietnam and
is also present on Christmas and Cocos Islands.
2.25
Australian citrus growing areas with climatic
conditions particularly suited to the establishment of citrus canker include
the Central Burnett region of Queensland,
the Central Coast
region of New South Wales and Darwin
in the Northern Territory. Other
major citrus production areas, such as the Riverland, Riverina and Sunraysia
districts are situated in much drier regions, making them less suitable areas
climatically for the establishment of the canker bacterium.
Previous Australian outbreaks
2.26
The first recorded outbreak of citrus canker was in the
Northern Territory in 1912. The
initial occurrence of the disease took 11 years to fully eradicate and resulted
in the destruction of every citrus tree north of latitude 19 degrees south.
2.27
In 1984, a program to eradicate citrus canker from Thursday
Island was initiated following the detection of the disease. Over
a two year period a total of 10 citrus trees were found to have canker symptoms
and were destroyed. No symptoms of citrus canker have been observed on Thursday
Island since February 1986, and the disease was declared
eradicated in September 1988.
2.28
Citrus canker was detected in the Northern
Territory again in 1991 and 1993. These incursions,
at the Lambell's Lagoon subdivision, about 50 kilometres from Darwin,
affected a small number of pummelo citrus trees. All affected trees were
destroyed, and the area was intensively monitored for two years. Citrus canker
was officially declared eradicated in the Northern
Territory in 1995.
2.29
The 1991-1993 incidence of citrus canker in the Northern
Territory was the last confirmed outbreak of citrus canker in Australia until
the disease was found in an orchard in Emerald, Queensland in late June 2004.
2.30
The importation of propagation material or fresh fruit
from overseas is one of the most likely ways citrus canker has been able to
enter Australia.
Travellers to Australia
who illegally import citrus plant material have been identified as one of the
primary risk pathways for the introduction of citrus canker into the country.
Authorities regularly intercept material infected with citrus canker from air
flight passenger baggage coming in from Asia and
arriving in Brisbane, Sydney or
Melbourne. Infected material has also been found in postal
items.[7]
Plant protection in the Australian federal system
Cooperation between
the Commonwealth and the states
2.31
In the Australian federal system, the Commonwealth and
the states share responsibility for plant protection. The Commonwealth Quarantine Act 1908, the Quarantine Proclamation 1998 and the Environment Protection and Biodiversity
Conservation Amendment (Wildlife Protection) Act 1999 operate alongside
state legislation to cover all issues relating to plant protection matters in Australia.
Department of
Agriculture, Fisheries and Forestry
2.32
All investigations into allegations of illegal importation
of plant material are conducted under the Commonwealth's Quarantine Act, which
is administered by the Department of Agriculture, Fisheries and Forestry
(DAFF). The Act provides for:
-
the prevention or control of the introduction,
establishment or spread of diseases or pests that will or could cause
significant damage to human beings, animals, plants, other aspects of the
environment or economic activities;
-
the declaration of a quarantinable disease;
-
the declaration of a quarantine area; and
-
a prohibition on the removal of plants and goods
from any part of Australia.
2.33
In addition to administering the Quarantine Act, DAFF
meets its quarantine obligations through:
-
risk assessments and scientific advice provided
by Biosecurity Australia (BA);
-
quarantine measures applied by the Australian
Quarantine and Inspection Service (AQIS) at points of entry into Australia;
-
involvement in specific measures at the
immediate post-border level.
2.34
A key role of the department is the national
coordination of responses to emergency pest and disease outbreaks which is
handled by the Product Integrity Animal and Plant Health Division of DAFF.[8]
State powers and legislation
2.35
Each state and territory jurisdiction has separate
quarantine and/or plant health legislation which prescribes their
responsibilities and powers. While all those involved agree that uniform
legislation across the states and the commonwealth would provide a stronger
framework for emergency management, that uniformity is still some way off, and
the Commonwealth, states and industry are yet to agree on the best way to
achieve it.
2.36
According to DAFF:
Overall, the State agencies are reasonably well placed in terms
of their legislative powers to respond to new pest incursions. However, there
are some areas where actions to contain or eradicate an outbreak may be
constrained by legislation, namely:
Few States have specific powers to destroy healthy plants or to
establish buffer zones to prevent the spread of an outbreak. [9]
2.37
The committee was concerned to hear that only Tasmania
and Victoria have passed the
necessary legislation to restrict the movement of people into or out of an area
affected by a pest. The committee strongly urges all states to learn from the
experience afforded by the citrus canker outbreak in Queensland
and to review their legislation in consultation with other states and the
relevant commonwealth agencies. A swift response to any disease outbreak is
crucial and it is often only possible on the basis of sound legislation.
2.38
In relation to pest incursions and quarantine issues,
state agencies have primary responsibility for:
-
post-entry surveillance and any incursions that
occur in their jurisdiction;
-
inter and intrastate quarantine operations;
-
the detection of new pest and disease outbreaks;
and
-
the collection of data on the status of animal
and plant health.
Plant Health Australia
- PLANTPLAN
2.39
In April 2000, a joint industry and government-owned
body known as Plant Health Australia (PHA) was established. PHA is a Corporations
Law company with membership that includes representatives from federal, state
and territory governments, and national representatives of plant industry
organisations. PHA is charged with coordinating national priorities for plant
health, and it has emphasised the need to develop an integrated approach to
national plant health policy development and implementation. In particular, PHA
has concentrated on emergency preparedness and response in the event of a plant
pest incursion.[10]
2.40
PHA's approach has been to develop PLANTPLAN – an
emergency plant pest response guide – as a framework for management of
infrastructure, actions and communications through all sectors involved in any
response to a disease.[11] PLANTPLAN
also includes a formal cost sharing agreement which covers government
and industry funding arrangements in the event of Emergency Plant Pest (EPP)
incursions.[12]
2.41
In accordance with PLANTPLAN guidelines, there are four
phases of response to an Emergency Plant Pest (EPP) incursion:
- Investigation Phase
– A pest is detected and reported to the Chief Plant Health Manager (CPHM)
of the state/territory agriculture department. The process of identification is
initiated and the relevant people and organisations are notified of the
suspected detection.
- Alert Phase – Identification of the pest is confirmed and the outbreak is declared. The
Chief Plant Protection Officer (CPPO) convenes a meeting of the Consultative Committee
on Emergency Plant Pests (CCEPP). The CCEPP will determine the feasibility of
eradication and make a recommendation to the National Management Group (NMG).
If the NMG decides to proceed with the eradication campaign, the CCEPP will
oversee the preparation of an EPP Response Plan by the lead Agency(s). The
resource requirements needed to implement the response and costings for the
eradication program will be identified. The NMG will approve the EPP Response
Plan and the national cost sharing arrangements to fund the campaign.
- Operational Phase – The Lead Agency(s)
in the state(s)/territory(s) in which the incursion occurs will implement and
manage the EPP Response Plan overseen by the CCEPP. The Lead Agency(s) will
provide regular reports to the CCEPP on the progress of the campaign. If
relevant, a Scientific Advisory Panel (SAP) will evaluate the effectiveness of
the response and its implementation.
- Stand Down Phase – After the
coordinated response is completed or if a review determines that eradication is
not feasible, records of expenditure and technical reports are provided to PHA
so that each state and territory's share of the cost can be calculated.[13]
2.42
Three of the four phases listed above have been
implemented in Emerald in response to the citrus canker outbreak with varying
degrees of success. Since the Emerald outbreak proved to be the first
opportunity to put in practice the PLANTPLAN guidelines, a number of lessons
have been learnt about how the plan operates in practice, which should enable
Plant Health Australia
to refine the guidelines to provide a better response in the event of another
emergency.
Preparedness to manage a citrus canker outbreak
2.43
In March 2004, prior to the confirmation of the
outbreak of canker in Emerald, government and industry had specifically
identified citrus canker as a disease that posed a possible threat to the
Australian citrus industry. The Office of the Chief Plant Protection Officer in
DAFF, in consultation with Australian citrus industry organisations prepared a Draft Contingency Plan for Citrus Canker
to form the basis for the emergency management of any future disease incursion.[14]
2.44
The Plan was based on the fire blight contingency plan,
the international phytosanitary standards and the experience of the Florida
Department of Agriculture and Consumer Services in dealing with citrus canker.[15]
2.45
In addition to summarising both the Australian
experience and international practices to contain and/or eradicate citrus
canker, the Plan identified two main principles for the eradication of citrus
canker:
- stopping the multiplication of bacteria on infected
plants; and
- preventing contact between non-infected susceptible
plants and the citrus canker bacterium.[16]
The National Management Group (NMG) and the CCEPP
2.46
Under PLANTPLAN, the response to the canker pest was
managed jointly by the Commonwealth and the state of Queensland, under the
auspices of the Primary Industries Ministerial Council/Primary Industries
Standing Committee framework with the other
states involved through the Citrus Canker National Management Group (NMG), a
body that comprised the CEOs of all state and territory agricultural agencies
and the chairs of Australian Citrus Growers and of Plant Health Australia.
2.47
A national Consultative Committee
on Emergency Plant Pests (CCEPP) was also convened to develop the control and
eradication programme. The NMG made determinations to deal with the outbreak
based on the advice received from the CCEPP. [17] Both the CCEPP and the NMG were guided
in their work by the Draft Contingency
Plan for Citrus Canker.
2.48
The committee will comment on the operations of the NMG
and of the CCEPP in Chapter 3.
The Emergency Plant Pest Response Deed
2.49
In addition to providing a set of national guidelines
for responding to emergency plant pest incursions, PLANTPLAN also includes a
formal cost sharing agreement which covers government and industry funding
arrangements in the event of Emergency Plant Pest (EPP) incursions.[18]
2.50
Unfortunately, when citrus canker was detected in
Emerald, the Emergency Plant Pest Response Deed (EPPRD)[19] was still being developed and its
signing and ratification was still fifteen months away. This had serious
ramifications for the way an important part of the management response to the
emergency was handled, namely, the central issue of funding the response to the
pest incursion and compensating the affected growers.
2.51
After five years of negotiation, the EPPRD was ratified
on 26 October 2005 by the
Commonwealth government, all state and territory governments and thirteen plant
industry members. In the event of a future outbreak, it will be used as a
template for deciding the funding arrangements: government and plant industry
signatories will share the costs, based on an assessment of the relative
private and public benefits flowing from the eradication of the particular pest
involved.
2.52
This means that some of the problems that arose in the
early phase of the emergency at Emerald should be avoided. Plant industry body Growcom
submitted to the committee that the Commonwealth and state agencies at the
forefront of the fight against citrus canker cooperated well and would have
achieved more if the funding issue had not worked against greater
cooperation:
While there has been a certain level of political manoeuvring
around the outbreak, at a professional bureaucratic level there has been
reasonable discussion, cooperation and cohesion among the technical and
bureaucratic staff involved in responding to and managing the outbreak.[20]
With an agreement in place, the fundamental principles of
funding the program would not have been an issue. Rather, the technical
approach to responding to the outbreak... could have been the prime focus of all
stakeholders.[21]
2.53
The committee hopes that through the implementation of
the EPPRD that the type of issues listed above will be addressed in future to
the satisfaction of farmers affected by pest incursions. The Deed also details
the timing of cost sharing arrangements. It is proposed that funding will
commence once the National Management Group endorses a recommendation from the
Consultative Committee on Emergency Plant
Pests (CCEPP) to eradicate a new pest incursion. The National Management Group
will also make the final decision on when cost sharing should cease. This is
likely to follow a recommendation from CCEPP that eradication has been achieved
or is no longer technically or economically feasible.[22]
2.54
The committee is pleased to note that the principles
underpinning the EPPRD and the guidelines for the reimbursement of owner costs
include:
-
growers being no worse off, or better off, as a
result of reporting a suspected exotic pest incursion; and
-
social justice for growers who, through no fault
of their own, are seriously affected by a decision to eradicate an exotic pest.
The 2004 outbreak in Emerald
2.55
On 28 June
2004, a private employee of Evergreen Farms sent a sample of what
he suspected was citrus canker to the Queensland Department of Primary
Industries and Fisheries (QDPI). Tests were conducted and on 2 July 2004, QDPI confirmed the sample as being
infected with citrus canker in accordance with the protocols established by
PLANTPLAN.[23] Under PLANTPLAN, Queensland
was responsible for developing the emergency response using the Draft Contingency Plan for Citrus Canker as
a basis for action.
2.56
The Draft Contingency Plan advocated that, with
National Management Group approval, the quarantine area to be treated should
include all infested trees and all citrus canker hosts within a defined area of
an infected tree, an approach based on the one used on canker infested citrus
plantations in Florida and often referred to by witnesses to the inquiry as "the
Florida protocol" (see Appendix 3
for more details).[24]
2.57
In the case of Emerald, the Consultative Committee on Emergency
Plant Pests (CCEPP) determined to operate at the maximum level and set the
radius of the destruction zone at 600 metres.[25]
A quarantine area was declared and steps taken to eradicate the canker on
Evergreen Farms using the so-called 'cookie-cutter' approach of destroying
trees within a 600 metre radius of where citrus canker had been found, imposing
a quarantine zone of 3.2 kilometre radius around it and a buffer zone involving
intense surveillance of a further 3.2 kilometre radius around the quarantine
zone.
2.58
While this process was being implemented, citrus canker
was detected on a second property (2PH Farms) and a third (the Iddles'
property) in the Emerald district on 5
October 2004 and 23 May
2005 respectively. As stated earlier, the committee decided to
conduct an inquiry into the outbreak in May 2005.
Positive cooperation
2.59
The committee deals with the way in which the Draft Contingency Plan for Citrus Canker
was implemented in response to the Emerald outbreak and reviews the operation
of the various management and consultative groups set up under PLANTPLAN in the
following chapter.
2.60
Inevitably, since it was the first time that those
response mechanisms were being put in practice, there were some problems, which
the committee will address in the next chapter. But the evidence before the
committee suggests that, from the time AQIS informed the relevant Queensland
state government agency of the situation, officers of QDPI and AQIS cooperated
fully with each other and worked well together throughout the 2001
investigation of possible illegal importation and the management of the
emergency response to the canker outbreak in 2004.
2.61
For example, an association of Queensland's
fruit and vegetable growers trading as Growcom, who dealt with the government
agencies involved told the Committee that:
While there has been a certain level of political manoeuvring
around the outbreak, at a professional bureaucratic level, there has been
reasonable discussion, cooperation and cohesion among technical and
bureaucratic staff involved in responding to and managing the outbreak.[26]
2.62
Growcom welcomed the level of professionalism shown and
stressed that it was absolutely essential that it be maintained because under the
Emergency Plant Pest Response Deed:
... industries and governments will be looking to invest in
biosecurity matters and will only do so where there is confidence in the
operations and implementation of those investments.[27]
Conclusion
2.63
The committee is strongly of the view that, as a result
of the lessons learnt in Emerald, all states must ensure that they have
legislation in place to ensure that appropriate compensation measures are
available to affected growers. In the case of Emerald, Queensland
state legislation provided for compensation only where healthy plants were
destroyed to prevent the spread of the pest. DAFF told the committee:
There is no uniform position across the States on the matter of
compensation for losses incurred as a result of eradication action;
For example, only the Queensland
Plant Protection Act 1989 provides
for compensation of owners of healthy plants that are destroyed as part of a
response programme; growers in a similar position in other States are not
entitled to compensation. [28]
2.64
Funding of the eradication programme and compensation
for affected growers are issues that lie at the heart of the implementation of
any emergency programme in response to a pest incursion. Not only because the
issue of how the costs are shared has the potential to influence the decisions
made by the Consultative Committee[29]
but also because it determines the level of cooperation that the response team
can expect from the affected growers. It is also a key element of any
rebuilding program after a pest incursion has been successfully dealt with.
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