The management of forest health in Victoria was a responsibility of the Forest Commission of Victoria since its inception in 1918 (Forest Act 1918). Good forest health relies on the involvement of all disciplines of forestry including silviculture, tree genetics, tree nutrition, tree physiology, forest entomology and pathology, and is underpinned by forest surveillance activities.

Forest pathology is concerned with the study of an infection of a tree host by a pathogen and examination of the environment in which the pathogen and host interact (i.e. Disease Triangle). The disease triangle includes predisposition of a host through genetics (i.e. resistance), the nutrition and physiology of a host, the virulence of a pathogen and the environment which allows for the interaction of a pathogen with the host. Management of disease relies on impacting one or more aspects of the triangle. It also incorporates any vectors responsible for spread.

The first Forest Pathologist appointed by the Forest Commission of Victoria (FCV) was Helen Lee (nee Purnell) who in the 1950’s examined the cause of Shoot Blight of Pinus radiata in the Ovens Valley (Purnell 1957), Cypress Canker (Purnell 1960), dieback caused by Armillaria sp in native forest at Mt Cole (Purnell 1959) and an unknown dieback on poorly drained native forests in East Gippsland (Lee 1962). During the 1950’s, disease studies were also undertaken by plantation research officers Ken Simpfendorfer, George Minko and Ken Eldridge. In July 1963 Dr. Geoffrey Marks was appointed Forest Pathologist which commenced a long and distinguished career in forest disease research during which he authored or co-authored more than 70 publications and five major books and reviews (Obit, 1990, Smith and Keane 1990). Forest pathologists Farouk Kassaby, John Kellas, Ian Smith and David Smith were added to the forest health research team over the next 40 years.

Soil Borne Pathogens

In 1969 Geoff Marks showed the cause of the dieback observed in East Gippsland in the 1950s, was associated with the soil-borne pathogen Phytophthora cinnamomi (Marks et al. 1972). This followed research by CSIRO (Dr. Frank Podger), who showed the pathogen as the cause of Jarrah dieback in Western Australia and was associated with disease in the Brisbane Ranges (Podger and Ashton 1970, Weste and Marks, 1974). Following this finding, the FCV instigated research into all aspects of the disease triangle in 1970s, and management actions to reduce disease impact. This continued throughout the 1970s and 1980s.

This research and actions taken included:

• Field and laboratory trials established to determine what eucalypt species were affected
• Quarantine zones implemented to protect the extensive areas of potential susceptible species of the alpine forests
• Studies undertaken on the biology of the pathogen including conducive climate and soils so as to elucidate areas of risk
• Selection for resistance from trees surviving the initial dieback
• Silvicultural approaches to reduce site hazard and provide seedbeds on which to sow seed to facilitate selection for resistance to the pathogen
• Surveillance of areas affected by the Biological Survey Branch

FCV research staff involved in this multi-discipline research included forest pathologists Dr. Geoff Marks, Farouk Kassaby, Dr. John Kellas and Ian Smith, forest entomologists Dr. Fred Neumann and John Harris, forest geneticist Dr. Leon Pederick, forest physiologist Dr. Jim Morris, soil scientists Don Hough and Simon Beams, forest silviculturists Peter Fagg, Peter Geary, Gary Featherston, Mark Cavill, Dr. Peter Woodgate, Mark Lutze, forest surveillance Bryan Ward, Bob McKimm, Bill Incoll, Ross Runnals, Peter McHugh, technicians Paul Clements, Ross Bickford amongst others, with statistical support by Bernie Aberli, Dr Kenneth Tregonning and Dr. Graham Hepworth with management oversight by Dr. Fred Craig, Dr. Jim Edgar, Barrie Dexter, Dr Ross Squire and Dr. David Flinn.

The initial trials/research highlighted eucalypt species susceptibility, conducive soils and climate and potential pathogenicity of other soil-borne pathogens (Kassaby et al. 1977, Marks and Smith 1980, 1981, 1983, Marks et al. 1985, Smith and Marks 1982, 1983, 1985, 1986, Smith et al. 1989). This research helped define the main risk of disease development to ash and stringybark eucalypts in coastal forests with low organic matter soils with poor structure and drainage and with soil temperatures generally exceeding 10^oC. This enabled a lifting of quarantine arrangements put in place to limit spread into susceptible alpine forests. The initial planting and laboratory trials also highlighted the potential for intraspecific resistance within susceptible species (Harris et al. 1983, 1985). This confirmed the development of management actions that included sowing of both susceptible and tolerant species on well prepared ash-beds with high sowing rates to promote selection for resistance and to lower soil and plant moisture found to be important in disease development (Marks and Smith 1991, Shearer and Smith 2000, Smith and Smith 2010). This research strategy facilitated successful regeneration of dieback sites that has been stable for over 50 years in East and South Gippsland.

Further cooperative research with plant pathologists and students from University of Melbourne (Dr. Gretna Weste), Latrobe University (Dr. Phillip Keane), Deakin University (Dr. David Cahill) and Murdoch University (Dr. Giles Hardy), helped to further elucidate the biology of P. cinnamomi particularly in highly susceptible understorey in National Parks, leading to a better understanding on the biology of the pathogen and development of control measures such as the use of phosphonate to improve host resistance and other fungicidal control (Marks and Smith, 1988, 1990, 1992, Ali et al. 1998, 2000). Research was also undertaken into novel methods to identify other Phytophthora species in streams and potential airborne spread by some species (Smith et al. 2007). This research led to input into several Forest Management Plans and the formulation of Victoria’s Public Land Phytophthora cinnamomi Management Strategy (DSE 2008) and the National Threat abatement plans for disease in natural ecosystems caused by Phytophthora cinnamomi (DEE 2018). Other newly identified and described Phytophthora species (eg. Phytophthora fallax (Cunnington 2010), Phytophthora niederhauserii (Abad et al. 2014), Phytophthora siskiyouensis, (Smith et al 2006) have also been identified and pathogenicity evaluated.

Foliage Pathogens

In spring 1974 in East Gippsland, over 4,200 ha of 120-180-year-old good quality Eucalyptus nitens, growing above 1000 m, were moderately to severely defoliated by a complex of leaf pathogens principally caused by the native fungus Aulographina eucalypti (Keane et al. 2000). This pathogen was also implicated in defoliation of E. regnans in the 1990s in the Central Highlands associated with a newly described native psyllid Cardiaspina bilobata. Despite the heavy leaf damage by the insect, petiole infection by the pathogen was shown to be the primary cause of defoliation (Coy et al. 1998), and tree deaths in gullies associated with secondary pathogens such as Armillaria spp. (Ian Smith observation). FCV and subsequent government research organisations, facilitated research on this and other eucalypt leaf pathogens with university plant pathologists, taxonomists and students (Carnegie et al. 1994, Keane et al. 2000, Barber et al. 2003, Pham et al. 2007a,b).

The pine plantation pathogen (Dothistroma septosporum, Dothistroma needle blight, DNB), was first recorded in NSW, Australia in 1976 and in Victoria in 1979 by Geoff Marks (Marks et al. 1989). Wind-borne spores of this pathogen most likely entered Australia from New Zealand. DNB can cause significant growth losses and as such again led to multi-disciplinary research in the 1980s and 1990s incorporating forest pathology (Geoff Marks, Ian Smith), forest genetics (Leon Pederick, Ian Bail), forest silviculture and forest surveillance activities supported by FCV, VPC and HVP regional foresters with research technical support by Paul Clements, Ross Bickford and Richard Stokes. Research and surveillance activities confirmed New Zealand research that showed that disease development was likely to be most severe in young, unthinned plantations in valleys and plateaus of elevations above 500 metres, where annual rainfall exceeded 1100 millimetres and catchment topography that favoured the collection of mist. Genetics trials also showed promise for DNB resistance which was developed into clones in the nursery that could be planted onto sites identified as being prone to disease development. From 1981, targeted surveillance of DNB principally consisted of drive-through surveys to map the distribution, severity and extent of the disease as it developed in Victoria. From 1991, a plot-based surveillance system targeting high-risk sites was developed to monitor DNB levels. These plots were used to trigger more intensive surveillance (e.g. by air) to enable early management intervention once levels reached predetermined thresholds (Smith et al 2008). HVP has continued to support this surveillance and management activity, now carried out by David Smith of Arborcarbon (previously with State Government of Victoria for 21 years), which has added more extensive plot based, aerial surveillance and remote sensing (drone and aerial technology) to the mix.

Forest Health Surveillance

Forest health surveillance (FHS) has been undertaken in Victorian native forests and plantations on an ad hoc basis since the early 1960s in response to incursions and outbreaks of native and introduced insect pests and plant pathogens, such as sirex wood wasp, Monterey pine aphid, Phytophthora dieback, phasmatids, psyllids, cup moths, gum-leaf skeletoniser and other defoliators (Smith et al. 2008). The purpose of surveillance is to provide a broad overview of forest health and data for land managers to allow them to take appropriate strategic decisions to manage risks to their estate and to highlight areas of research needed to reduce the risk. Early targeted FHS in Victoria consisted mainly of drive-through surveys with aerial surveillance where required to determine the extent of a particular damaging agent. The 1991 plot-based surveillance for Dothistroma was extended in 2001 into a broader plot-based monitoring system implemented for HVP Plantations (450 monitoring plots) as part of its risk management program to determine the status, changes and trends in tree health on an annual basis, and provide data for management decisions to control outbreaks threatening the health of plantations. Routine aerial FHS across HVP Plantations started in 2008 and is now undertaken across most pine growing forest owners in Victoria (Smith et al 2008). A pilot study in state-owned native forest using similar methods commenced in 2007. Research staff involved in the setup of the plot network and its surveillance included Ian Smith, David Smith, Nick Collett, Paul Clements, Carolien Schoenborn, Richard Stokes, Mike McCormick and Ben Smith. Since 1998 this surveillance has also formed part of Victoria’s contribution to Australia’s 5-yearly State of the Forest Reports.

Forest Nurseries

Research in both container grown and open rooted seedlings in nurseries has been a priority for FCV pathologists from the earliest inception of the research branch. Control of soil-borne pathogens in particular became a priority following the identification of P. cinnamomi as the cause of dieback in native forests, the recorded susceptibility of radiata pine seedlings and the potential for nursery stock to spread the pathogen. Development of quarantine protocols and use of washdown chemicals and pesticides, interaction with herbicides and salt, and solar sterilisation of nursery beds were all part of research undertaken by Geoff Marks, George Minko, Farouk Kassaby, and Ian Smith with assistance from the other research disciplines. The Rennick nursery also had a significant issue in the 1980s with root nematodes Pratylenchus penetrans and Rotylenchus robustus and control measures were developed in association with Department of Agriculture nematologist Winoto Suatmadji. Pine nursery pathogen research was continued with VPC and from 1998 HVP Plantations. The move to fully containerised plants with appropriate quarantine protocols, has considerably reduced the impact of soil-borne pathogens.

Other Forest Health Issues

Other forest pathology research carried out by FCV and subsequent Forestry Research Departments cover a diverse range of forest diseases and organisms, including wood decay, mycorrhizae of conifers, Diplodia dieback, nematodes in forest tree nurseries and ferns, leaf rusts in poplars, indigenous leaf pathogens in native forests and eucalypt plantations, indigenous Myrtle Wilt of Nothofagus and the native root and trunk infecting fungus Armillaria in native forests with Dr John Kellas in association with CSIRO Scientist Dr Glen Kile. The research undertaken to define the parameters impacting disease development has resulted in management options to reduce disease impact.

Another potentially serious disorder of eucalypts and other native vegetation in Australia was Mundulla Yellows which was first observed by bee-keeper Geoff Cotton in 1973 near Mundulla, South Australia (Keane et al 2000). It was described as a progressive dieback syndrome of eucalypts and other native species. It has been reported as occurring in most states of Australia, and in Europe, USA and South America. With the concern and early research suggesting that this was a biotic disease that was spreading, a Mundulla Yellows Task Group was formed in 2002 funded by Australian Department of the Environment and Heritage. The multi-disciplinary team formed consisted of a molecular plant pathologist (Dr. Jo Luck), virologist (Dr. Rosa Crnov), a soil scientist (Barbara Czerniakowski), from the Victorian Department of Primary Industries, and a forest pathologist (Ian W. Smith) from the Victorian Department of Sustainability and Environment. The team was supported by other scientists from their respective departments including mycologists, entomologists, botanists, ecologists with technical assistance as required (Crnov et al. 2004). After extensive field, laboratory and glasshouse trials it was concluded that biotic agents were not responsible for the symptoms observed, and the cause related to high soil pH created by either limestone gravel applied to roads or high pH bore water causing a physiological iron deficiency within the trees. Potential control measures were suggested (Luck et al. 2006, Czerniakowski et al. 2005, 2006). This again highlighted the importance of a multi-disciplinary approach to complex disease issues.

Research Working Group 7

The forest health research team was also called upon to investigate and assist in the management of new introductions of pests and pathogens to Australia. The National Research Working Group system (RWG7, Forest Health) which included the New Zealand Forest Research group, played an important role in developing cooperation and collaboration between State, Federal and international organisations responsible for Forest Health. This was particularly important for development of management options for Sirex, Dothistroma and other exotic organisms to Australia and New Zealand.

This collaborative working group also led to the development of a National Generic Incursion Management Plan (GIMP) for the Forest Industry which provided for response plans and cost sharing arrangements to be initiated (Gadgil 2000). It was to be funded by imposing a levy on those who create the risk of introducing exotic pests and pathogens, and would have provided base funding for monitoring of high-risk sites and an increase in diagnostic capabilities. While the plan was initially approved of by the national forest ministerial council, federal treasury stopped its implementation declaring it a new tax. The GIMP was tested in 2000 when an unknown Bursphalenchus nematode was isolated from a rapidly dying Pinus halepensis in the Williamstown botanic gardens near the ports by DPI Crop Health Services mycologist Ian Pascoe, nematologist Dr. Lila Nambiar, and plant pathologist Dr Ramaz Aldaoud. This was the first record for Australia of this nematode and the first detection of this species outside China (Smith et.al. 2008). Collaboration with CSIRO nematologist Dr Mike Hodda led to its subsequent identification as Bursaphelenchus hunanensis.

Aerial and ground-based surveillance showed the location of all dying pines infested with the nematode, and the trees were removed and deep buried in a quarantine tip. The nematode was thus successfully eradicated through this targeted campaign combined with poor vector establishment. The success of this program was significant because it demonstrated that eradication may be a viable strategy for dealing with incursions of exotic organisms and the importance of early detection (Hodda et al. 2008). The GIMP was subsequently merged into PlantPlan, which incorporates nationally consistent guidelines for managing a response to an emergency plant pest incident. Experience from this incursion also led to greater involvement in surveillance by local council arborists in early detection within urban forests (Smith 2004, Lefoe et al. 2007), and the collation of extensive council tree databases coordinated by David Smith to aid in surveillance activities. The forest health team (Ian Smith, Nick Collett and David Smith) also played a major role in the development and implementing of surveillance programs for identified major exotic insect pests and pathogens including involvement in national insect trapping programs, monitoring Melbourne Elms for Dutch Elm Disease, Elm Leaf beetle, Fusarium Wilt of Canary Island Date Palm (Summerell et al. 2006), exotic wood wasps and beetles and recent introduction of Myrtle Rust (2010), Chestnut Blight (2010) and Giant Pine Scale (2014). Ian Smith was also involved in 2009 with the assessment offshore (USA) of Phytophthora ramorum a potential serious airborne pathogen of native forests in Victoria and Australia (Huberli et al. 2007, Dell et al. 2009, Ireland et al. 2012a, b).

Forest Health Education

Education in forest health for foresters and arborists was also one of the roles undertaken over the years by the Forest Health team with lectures and practicals undertaken for the University of Melbourne Forest Diploma, Forest Science and Masters Degrees, and the Urban Horticulture Course. This was initially led by Geoff Marks and Fred Neuman and in later years by Ian Smith, Nick Collett and David Smith. Education in Forest Health pests and pathogens was also the focus of several books (Marks et al. 1982, Smith et al. 2008) and Research and Development Notes published by the FCV and subsequent Victorian government forest departments (CFL 1986, CFL 1987, CNR 1992a, CNR 1992b, NRE 1996, Smith 2001, Smith 2003 and Smith 2005).

Forest Health Team

In the 1980s the FCV forest health team consisted of 3 forest pathologists 2 forest entomologists 2 experienced technicians and access to other forest disciplines and the biological survey branch. With the disbandment of the FCV in 1983, the implementation of a purchaser/provider model for research in 1985, and the imposition of government staff freezes with no replacement, expertise within Victorian government department responsible for forest health reduced to one staff member between 2010 and 2022 and due to restructures this number is now zero. Forest health is now conducted by a small number of dedicated private forest pathologist/entomologists (previously State Government staff) outside of the government system.

References

References in this article will be found in the bibliography available below:

Bibliography