Paul Barber

Over the years, we have conducted surveys, carried out monitoring, diagnosed health disorders, and treated a wide range of vegetation species throughout golf courses, parks, gardens and reserves in Australia and south-east Asia. Although vegetation within these growing environments can face similar challenges in both regions, there are many differences, including the vegetation species, pests and pathogens, climate, soil type, application of chemicals, type of management. The focus of this paper will be mainly on managing trees in Australia.

Surveys of nurseries and plantations of Eucalyptus species were conducted within Lao PDR in 2009. A range of pathogens were isolated including species within Phytophthora, Pythium, Fusarium, Colletotrichum, Neofusicoccum, Lasiodiplodia, Pilidiella, Calonectria, Cryptosporiopsis, Corticium and Teratosphaeria. Some diseases caused significant defoliation and loss of stock within nurseries and plantations. The presence of these diseases in combination with a changing climate poses many challenges for the future sustainable and profitable management of plantations in Lao PDR.

Remote sensing of vegetation condition using high resolution digital multispectral imagery (DMSI) is an option for land managers interested in quantifying the distribution and extent of dieback in native forest. Crown condition is assessed as reference to the physical structure and foliage (i.e. density, transparency, extent and in-crown distribution) of a tree crown. At 20 sites in the Yalgorup National Park, Western Australia, a total of 80 (Eucalyptus gomphecephala) crowns are assessed both in-situ and using 2 acquisitions (2008 and 2010) of airborne DMSI. Each tree was assessed using four crown-condition indices: Crown Density, Foliage transparency, and the Crown Dieback Ratio and Epicormic Index. DMSI data is trained against canopy condition assessment data from 2008, crown condition is predicted using only spectral data. Comparison of DMSI derived Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI) and a novel Red Edge Extrema Index (REEI) suggests the REEI is more suited to classification applications of this type.

Since the early 1990s there has been a significant decline of E. gomphocephala, and more recently E. marginata, in the tuart forest in tuart woodland in Yalgorup National Park SW Western Australia, although no satisfactory aetiology has been established to explain the decline. Characteristics of the canopy dieback and decline distribution are reminiscent of other forest declines known to involve Phytophthora soil pathogens and indicate that a Phytophthora species may be involved in the decline. In 2007 isolates of Phytophthora multivora, recently described by (1), were recovered from rhizosphere soil of declining or dead trees of Eucalyptus gomphocephala and E. marginata. For E. gomphocephala and E. marginata, the pathogenicity of P. multivora was tested: ex situ on seedlings using a soil infestation method; and in situ on stems using an under bark infestation method.

Tuart is a magnificent woodland tree endemic to the Swan Coastal Plain of Western Australia, and is one of the few eucalypts that is adapted to calcareous soil profiles (1). Prior to European settlement there were more than 111,600 ha of tuart woodlands (2) but this has been reduced to 30,311 mostly as a result of clearing for urban development and agriculture (3). In the early 1990’s the decline of tuart woodlands in Yalgorup National Park (YNP), 1.5 hours south of Perth, became severe causing public awareness and concern. At present, the majority of the 13,000 hectares of this park is affected. A large research group was established in 2003 to investigate the cause(s) of this decline, conducting research on a range of abiotic and biotic factors, including water relations and hydrology, environmental correlates, fire and competition, mycorrhizae and nutrition, fungal pathogens and insect pests. The collaborative, integrated and adaptive approach to the research, and the latest findings of the group will be presented.