Our scientists are committed to conducting world-class research and communicating their findings in international peer reviewed publications.

2015

Scott, P.M., Barber, P.A., Hardy, G.E.St.J. (2015) Novel phosphite and nutrient application to control Phytophthora cinnamomi disease. Australasian Plant Pathology DOI 10.1007/s13313-015-0365-4

Systemic treatment of stems with injections of phosphite liquid and novel soluble capsule implants of phosphite, PHOSCAP® (phosphorous, potassium, iron, manganese, zinc, boron, copper, magnesium and molybdenum) and MEDICAP MD® (nitrogen, phosphorous, potassium, iron, manganese, and zinc), were applied to Banksia grandis and Eucalyptus marginata trees to control Phytophthora cinnamomi. Four weeks after treatment application, excised branches were under-bark inoculated with P. cinnamomi. In B. grandis, phosphite implants and liquid injections significantly reduced lesion length compared to the control, and MEDICAP MD® implants; however, there was no significant difference in lesion length between trees treated with phosphite implants and liquid injections and PHOSCAP implants.

In E. marginata, phosphite implants and liquid injections significantly reduced lesion length compared to the control, PHOSCAP® and MEDICAP MD® implants. In B. grandis and E. marginata, PHOSCAP® and MEDICAP MD® implants reduced the average lesion length compared to the control; however, the interactions were not significant. Results show that both liquid phosphite injections and novel phosphite implants are effective at controlling lesion extension in B. grandis and E. marginata, caused by P. cinnamomi. Further work is required to determine if nutrient application reduces Phytophthora disease through improving plant health.

Crous, P.W., Wingfield, M.J….Barber, P.A.,…Groenewald, J.Z. (2015) Fungal Planet description sheets: 320-370. Persoonia 34: 167-266.
Novel species of fungi described in the present study include the following from Malaysia: Castanediella eucalypti from Eucalyptus pellita, Codinaea acacia from Acacia mangium, Emarcea eucalyptigena from Eucalyptus brassiana, Myrtapenidiella eucalyptorum from Eucalyptus pellita, Pilidiella eucalyptigena from Eucalyptus brassiana and Strelitziana malaysiana from Acacia mangium. Furthermore, Stachybotrys sansevieriicola is described from Sansevieria ehrenbergii (Tanzania), Phacidium grevilleae from Grevillea robusta (Uganda), Graphium jumulu from Adansonia gregorii and Ophiostoma eucalyptigena from Eucalyptus marginata (Australia), Pleurophoma ossicola from bone and Plectosphaerella populi from Populus nigra (Germany), Colletotrichum neosansevieriae from Sansevieria trifasciata, Elsinoë othonnae from Othonna quinquedentata and Zeloasperisporium cliviae (Zeloasperisporiaceae fam. nov.) from Clivia sp. (South Africa), Neodevriesia pakbiae, Phaeophleospora hymenocallidis and Phaeophleospora hymenocallidicola on leaves of a fern (Thailand), Melanconium elaeidicola from Elaeis guineensis (Indonesia), Hormonema viticola from Vitis vinifera (Canary Islands), Chlorophyllum pseudoglobossum from a grassland (India), Triadelphia disseminata from an immunocompromised patient (SaudiArabia), Colletotrichum abscissum from Citrus (Brazil), Polyschema sclerotigenum and Phialemonium limoniforme from human patients (USA), Cadophora vitícola from Vitis vinifera (Spain), Entoloma flavovelutinum and Bolbitius aurantiorugosus from soil (Vietnam), Rhizopogon granuloflavus from soil (Cape Verde Islands), Tulasnella eremophila from Euphorbia officinarum subsp. Echinus (Morocco), Verrucostoma martinicensis from Danaea elliptica (French West Indies), Metschnikowia colchici from Colchicum autumnale (Bulgaria), Thelebolus microcarpus from soil (Argentina) and Ceratocystis adelpha from Theobroma cacao (Ecuador). Myrmecridium iridis (Myrmecridiales ord. nov., Myrmecridiaceae fam. nov.) is also described from Iris sp. (The Netherlands). Novel genera include (Ascomycetes): Budhanggurabania from Cynodon dactylon (Australia), Soloacrosporiella, Xenocamarosporium, Neostrelitziana and Castanediella from Acacia mangium and Sabahriopsis from Eucalyptus brassiana (Malaysia), Readerielliopsis from basidiomata of Fuscoporia wahlbergii (French Guyana), Neoplatysporoides from Aloe ferox (Tanzania), Wojnowiciella, Chrysofolia and Neoeriomycopsis from Eucalyptus (Colombia), Neophaeomoniella from Eucalyptus globulus (USA), Pseudophaeomoniella from Olea europaea (Italy), Paraphaeomoniella from Encephalartos altensteinii, Aequabiliella, Celerioriella and Minutiella from Prunus (South Africa). Tephrocybella (Basidiomycetes) represents a novel genus from wood (Italy). Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

2014

Yulia, E., Hardy, G., Barber, P.A., Dell, B. (2014) A severe canker disease of Corymbia ficifolia caused by Quambalaria coyrecup in native and urban forests of Western Australia. Forest Pathology DOI: 10.1111/efp.12082
A serious canker disease is affecting the health of Corymbia ficifolia in urban areas of Perth, Western Australia. Quambalaria coyrecup was frequently associated with diseased trees and its presence confirmed by morphological characters and DNA sequencing. A number of Quambalaria species have previously been identified as causal agents of canker and shoot blight diseases on a range of Eucalyptus and Corymbia species. It was therefore the aim, using glasshouse studies, to determine whether Q. coyrecup was the primary causal agent of the cankers on C. ficifolia and whether other Quambalaria species could also be associated with the disease. All seedlings inoculated with Q. coyrecup produced canker symptoms within 1 month after inoculation. Canker lesions typical of those observed in the field also occurred in the four subsequent months, after which time the trial was terminated. Inoculation with Q. cyanescens and Q. pitereka (isolated from C. ficifolia shoots) did not result in lesion development. This study establishes that Q. coyrecup is a serious pathogen of C. ficifolia and that wounding is required for canker development to occur. The management of Quambalaria canker must therefore include the minimization of artificial wounding of trees in the nursery and field.

2013

Barber, P.A., Paap, T., Burgess, T.I., Dunstan, W., Hardy, G.E.StJ. (2013) A diverse range of Phytophthora species are associated with dying urban trees in an Australian capital city. Urban Forestry & Urban Greening 12: 569-575.

Surveys of dying vegetation throughout the urban forest of Perth and surrounds revealed symptoms typical of those produced by Phytophthora species. A total of nine Phytophthora species, including P. alticola, P. multivora, P. litoralis, P. inundata, P. nicotianae and P. palmivora were isolated. In addition, three previously undescribed species, Phytophthora aff. arenaria, Phytophthora aff. humicola and Phytophthora sp. ohioensis were isolated. Isolates were recovered from a wide range of native and non-native host genera, including Agonis, Allocasuarina,, Brachychiton, Calothamnus, Casuarina, Corymbia, Dracaena, Eucalyptus, Ficus, Pyrus and Xanthorrhoea growing within streetscapes, parks and gardens, and remnant bushlands. Phytophthora multivora was the most commonly isolated species. Very little is currently known about the distribution of these species, their origin, and pathogenicity to many of the important tree species growing within the urban environment. These pathogens may play a key role in the premature decline in health of the urban forest throughout Perth, and should be managed according to the precautionary principle and given high priority when considering future sustainable management strategies.

Barber, P.A and Wilson, D. (2013) Airborne turf health monitoring. Australian Turfgrass Management Journal 15.6, 44-45.

No abstract currently available.

Barber, P.A. (2013) Restoring the canopy health of declining native trees. Western Wildlife 17: 8-10.

The rapid decline in health of native trees across the south-west of WA over recent years is causing great concern. Over the past two years we have had many enquiries from landholders about the cause(s) of decline of their trees, and whether there is anything they can do to alleviate this decline.  The loss of old, significant trees can be devastating for the landholder, not to mention for the associated flora and fauna reliant upon these iconic and dominant canopy species.

Evans, B., Stone, C., Barber, P. (2013) Linking a decade of forest decline in the southwest of Western Australia to bioclimatic change. Australian Forestry DOI:10.1080/00049158.2013.844055

No abstract currently available.

Scott, P.M., Dell, B., Shearer, B.L, Barber, P.A., Hardy, G.E.StJ. (2013) Phosphite and nutrient applications as explorative tools to identify possible factors associated with Eucalyptus gomphocephala decline in southwestern Australia. Australasian Plant Pathology DOI 10.1007/s13313-013-0243-x

Tree declines are increasingly being reported around the world.  Since the 1990’s Eucalyptus gomphocephala (tuart) has suffered a significant decline in the Yalgorup region, approximately 100 km south of Perth Western Australia.  The complexity of many tree declines makes diagnosis difficult.  Robust tools are needed to help diagnose and distinguish factors contributing to tree declines.  Two experiments tested the effect of trunk applied phosphite, nutrients and combined phosphite and nutrient treatments on wild declining Eucalyptus gomphocephala.  Treatment efficacy was tested as a management option to mitigate crown decline and as an explorative tool to help determine disease causality.  Experiment 1 assessed the efficacy of combined treatments of trunk injections of different phosphite concentrations, trunk nutrient implants of different compositions and combined phosphite and nutrient treatments.  Experiment 2 assessed the efficacy of different phosphite concentrations.  In Experiment 1, phosphite, together with nutrient treatments, increased average crown condition by 21%, as measured using a crown health score (CHS) averaged over 4 years, with the greatest improvements 6 months after application. Injection of 25 g phosphite/L combined with 0.3 g zinc sulphide gave the greatest increase.  In Experiment 2, 75 to 375 g phosphite/L increased the CHS compared to the control blank treatments but the best treatment (150 g phosphite/L) only improved the CHS by 10%.  Foliar analysis for Experiment 2 confirmed a significant uptake of phosphite for all phosphite treatments.  Phosphite application did not affect foliar nutrient concentrations.  The increase in the CHI and significant flushes in new growth resulting from phosphite and nutrient treatments highlight the possible involvement of Phytophthora species in the decline, as Phytophthora species are known to be controlled by phosphite application.  Further work on combined phosphite and nutrient applications, with a particular emphasis on zinc, is required to help understand and potentially mitigate the E.gomphocephala decline syndrome.

Ishaq, L., Barber, P.A., Hardy, G.E.StJ., Calver, M., Dell, B. (2013) Seedling mycorrhizal type and soil chemistry are related to canopy condition of Eucalyptus gomphocephala. Mycorrhizae 10.1007/s00572-012-0476-5.

The health of Eucalyptus gomphocephala is declining within its natural range in south-western Australia. It is hypothesised that changes in mycorrhizal fungi and soil chemistry might be associated with E. gomphocephala decline. A containerised bioassay experiment with E. gomphocephala as the trap plant was set up using intact soil cores collected from 12 sites with E. gomphocephala canopy condition ranging from healthy to declining. Adjacent soil samples were collected for chemical analysis. The study revealed that the type of mycorrhiza (arbuscular or ectomycorrhizal) formed in seedlings predicted the canopy condition of E. gomphocephala at the sites where the cores were taken. Ectomycorrhizal fungi colonization was higher in seedling roots in soil from sites with healthy canopies, whereas colonization by arbuscular mycorrhizal fungi dominated in roots in soil from sites with declining canopies. Furthermore, a number of soil chemical properties predicted both canopy condition and the type of mycorrhizal fungi that colonised roots. These findings suggest the need to quantify those ECM fungi that are sensitive to E. gomphocephala canopy decline and the possibility to use ECM fungi as predictors of future E. gomphocephala decline.

Keywords: Tree decline. Soil nutrients.  Ectomycorrhizae. Canopy health.

Evans, B., Lyons, T., Barber, P., Stone, C., Hardy, G. Enhancing a eucalypt crown condition indicator driven by high spatial and spectral resolution remote sensing imagery. Journal of Applied Remote Sensing 6: 063605-1-063605-15

The condition of Eucalyptus gomphocephala tree crowns was assessed on ground and using two condition classification models to understand changes in forest health, tree by tree, through space and time. Using high resolution (0.5 m) digital multispectral imagery, predictor variables were derived from textural, spectral and geometric variance characteristics of all pixels inside the crown area. The results estimate crown condition as a surrogate for tree health against the total crown health index. Crown condition is derived from combining ground based crown assessment techniques of density, transparency, dieback and the regrowth of foliage. This object based approach summarizes the pixel data into mean crown indices assigned to crown objects which became the carrier of information.   Models performed above expectations, with substantial and significant weighted Cohen’s kappa (κ > 0.60 and p < 0.001) using 70% of available data. Using all available 2008 in-situ data for model development, crown condition was predicted forwards (2010) and backwards (2007) in time, capturing declining and recovering trends in crown condition, identifying decline in the healthiest between 2008 and 2010. The results confirm that combining spectral and textural information increased model sensitivity to small variations in crown condition. The methodology provides a cost-effective means for monitoring crown condition of this or other eucalypt species in native and plantation forests. 

Keywords: tree crown condition; forest health; canopy dieback; high resolution; digital multispectral imagery; remote sensing; Eucalyptus gomphocephala; tuart; random forest

Scott, P.M., Shearer, B.L., Barber, P.A. and Hardy, G.E.StJ. (2013) Relationships between the crown health, fine root and ectomycorrhizae density of declining Eucalyptus gomphocephala. Australasian Plant Pathology 10.1007/s13313-012-0152-4

The fine root and ectomycorrhizal system of 18 declining Eucalyptus gomphocephala trees, in the Yalgorup region, approximately 100km south of Perth, Western Australia, were exposed using an air spade and the relationship between the crown health and the fine root and ectomycorrhizal total density scores (TDS) was determined.  Crown health was significantly correlated with the fine root and ectomycorrhizal TDS’s and trees with crown decline symptoms had significantly fewer fine root and ectomycorrhizae than trees with healthy crowns.  In addition, E. gomphocephala seedlings were grown in-situ within the exposed fine root mats adjacent to the 18 woodland trees and the relationship between seedling and tree health was assessed.  Seedlings survival, height and foliar health were significantly correlated with the crown health of the adjacent woodland trees.  Seedling survival was also significantly correlated with the ectomycorrhizae TDS of the adjacent woodland trees.  The relationship between reduced seedling health and reduced crown health and ectomycorrhizal density of the woodland trees indicates that decline symptoms may be associated with the absence of ectomycorrhizae.  The study demonstrates new techniques for assessing the fine root and ectomycorrhizal densities of large woodland trees and their relationships to crown health. 

Keywords Declining, Eucalyptus gomphocephala, Crown health, Fine root, Ectomycorrhizae density, Phytophthora multivora, Air spade.

Evans, B., Lyons, T.J., Barber, P.A., Stone, C., Hardy, G. (2013) Dieback classification modelling using high resolution digital multi spectral imagery and in situ assessments of crown condition. Remote Sensing Letters 3: 541-550.

Quantifying dieback in forests is useful for land managers and decision makers seeking to explain spatial disturbances and understand the cyclic nature of forest health. Crown condition is assessed as reference to dieback in terms of the density, transparency, extent and in-crown distribution of foliage. At 20 sites in the Yalgorup National Park, Western Australia, a total of 80 Eucalyptus gomphocephala crowns were assessed both in situ (2008) and using two acquisitions (2008 and 2010) of airborne imagery. Each tree was assessed using four crown-condition indices: Crown Density, Foliage Transparency, the Crown Dieback Ratio and Epicormic Index combined into a single index called the Total Crown Health Index (TCHI). The airborne imagery is like value calibrated then classified and modelled using in situ canopy condition assessments resulting in a quantification of crowncondition change over time. Comparison of Normalized Difference Vegetation Index (NDVI), Soil-Adjusted Vegetation Index (SAVI) and a novel Red-Edge Extrema Index (REEI) suggests that the latter is more suited to classification applications of this type.

2012

Barber, P.A. & Hardy, G.E.StJ. (2012) Restoring the canopy health of native urban bushland and parkland trees. Australasian Plant Conservation 21: 23-24.

The population of Western Australia’s capital city, Perth, is rapidly expanding and will continue to do so over the coming decade.  In comparison to capital cities of the eastern states, the density of people per square kilometer is low.  These trends are often portrayed in the media and the business sector as good, however, what does this all mean for native trees in urban bushlands and parklands? The canopy cover of this native vegetation has dramatically reduced over recent years largely as a result of property development, and what remains has become increasingly fragmented and in a very poor state of health, due to a range of factors. Urban bushland restoration is traditionally viewed in the context of weed control, and revegetation, but what about the restoration of the health of the existing canopy tree species?  This article briefly discusses the causes of decline of these species, the importance of restoring their canopy health, and novel methods that have been applied to do so.

Barber, P., Burgess, T., Paap, T., Hardy, G. (2012) Phytophthora species associated with disease in peri-urban woodland and forest ecosystem. 6th meeting of IUFRO working party Phytophthora in forests and natural ecosystems, Cordoba, Spain 9-14th September.

No abstract currently available.

Barber, P.A., Thu, P.Q., Hardy, G.E., Dell, B. (2012) Emerging disease problems in eucalypt plantations in Lao PDR. IUFRO international diseases and insect of tropical forest trees, Yogyakarta, Indonesia 8th-10th October.

No abstract currently available.

2011

Taylor, K., Andjic, V., Barber, P.A., Hardy, G.E.StJ., Burgess, T.I. (2011) New species of Teratosphaeria associated with leaf diseases on Corymbia calophylla (marri). Mycological Progress 11: 159-169

Corymbia calophylla is an important eucalypt species endemic to the south-west of Western Australia. It is currently in decline across its native habitat for unknown reasons but perhaps due to climate change or to the presence of a recently described canker disease caused by Quambalaria coyrecup. Few fungal leaf pathogens have been described from C. calophylla. The following paper describes two new species of Teratosphaeria from C. calophylla, Teratosphaeria calophylla sp. nov and T. rubidae sp. nov. In addition, a new epitype was designated for T. australiensis.

Keywords: Quambalaria, Epitype, Taxonomy, Teratosphaeria australiensis . Tree decline

>Scott, P.M., Jung, T., Shearer, B.L., Barber, P.A., Calver, M.C., Hardy, G.E.StJ. (2011) Pathogenicity of Phytophthora multivora to Eucalyptus gomphocephala and E. marginata. Forest Pathology doi: 10.1111/j.1439-0329.2011.00753.x

Phytophthora multivora is associated with the rhizosphere of declining  Eucalyptus gomphocephala,  E. marginata and Agonis flexuosa. Two pathogenicity experiments were conducted. The first experiment examined  ex situ the pathogenicity of five  P. multivora isolates and one  P. cinnamomi isolate on the root systems of  E. gomphocephala and one  P. multivora isolate on the root system of  E. marginata. In the second experiment, the pathogenicity of  P. multivora  to  E. gomphocephala and  E. marginata saplings was measured  in situ using under-bark stem inoculation. In experiment one; the  P. cinnamomi isolate was more aggressive than all  P. multivora isolates causing significant loss of fine roots andplant death. Two  P. multivora isolates and the  P. cinnamomi isolate caused significant losses of  E. gomphocephala fine roots 0-2 mm in diameter and significantly reduced the surface area of roots 0-1 mm in diameter. One  P. multivora and the  P. cinnamomi isolate significantly reduced the surface area of roots 1-2 mm in diameter. Two of the  P. multivora isolates significantly reduced the number of  E. gomphocephala root tips. In  E. marginata the length and surface area of roots 0-1 mm in diameter and number of root tips, were significantly reduced by  P. ultivora infestation. Rhizosphere infestation with the  P. multivora isolates and  P. cinnamomi isolate on  E. gomphocephala, and one  P. multivora isolate on  E. marginata, did not significantly influence the foliar nutrient concentrations. In experiment two, under-bark inoculation with  P. multivora caused significant lesion extension in  E. gomphocephala and  E. marginata saplings, compared to the control. We propose that  P. multivora is inciting  E. gomphocephala and  E. marginata decline by causing fine root loss and subsequently interfering with nutrient cycling throughout the plant. The impact of fine root loss on the physiology of plants in sites infested with  P. multivora requires further research.

Key words: Tuart, jarrah, dieback, root analysis, fine root loss, air spading, soil infestation and under bark inoculation.

Barber, P.A., Crous, P.W., Groenewald, J.Z., Pascoe, I.G., Keane, P. (2011) Reassessing Vermisporium (Amphisphaeriaceae), a genus of foliar pathogens of eucalypts. Persoonia 27: 90-118.

The genus Vermisporium presently accommodates 13 species, 11 of which are associated with leaf spots of eucalypts in the Southern Hemisphere. Vermisporium is chiefly distinguished from Seimatosporium (Amphisphaeriaceae) on the basis of a short exogenous basal appendage, and the absence of a recognisable apical appendage. Due to the increasing importance of these species in native forests, and confusion pertaining to their taxonomy, a revision of the genus was undertaken based on fresh collections and dried herbarium specimens. Results from DNA sequence data analyses of the nrDNA-ITS and 28S nrRNA genes for species of Vermisporium indicated the genus to be a synonym of Seimatosporium. New combinations are introduced in Seimatosporium for several species: S. acutum, S. biseptatum, S. brevicentrum, S. obtusum, S. orbiculare, S. verrucisporum and S. walkeri. An updated key to all species occurring on eucalypts is also provided.

Keywords: Australia, Eucalyptus, foliar pathogen, Seimatosporium, Taxonomy

Andjic, B., Dell, B., Barber, P., Hardy, G., Wingfield, M., Burgess, T. (2011) Plants for planting; indirect evidence for the movement of a serious forest pathogen, Teratosphaeria destructans, in Asia. European Journal of Plant Pathology 131: 49-58.

Fungal diseases caused by native pathogens and pathogens introduced with planting stock have a significant impact on exotic plantation forestry in the tropics. Teratosphaeria destructans (formerly Kirramyces destructans) is a serious pathogen causing leaf, bud and shoot blight diseases of Eucalyptus spp. in plantations in the sub-tropics and tropics of south-east Asia. This pathogen was first discovered in Indonesia in 1995 and has subsequently spread to Thailand, China, Vietnam and East Timor. The biology, ecology and genetics of this important pathogen have not been explored yet. The objective of this study was, thus, to determine the genetic diversity and movement of T. destructans throughout south-east Asia using multi-gene phylogenies and microsatellite markers. Out of nine gene regions only two microsatellite markers detected a very low nucleotide polymorphism between isolates; seven other gene regions, ITS, β-tubulin, EF1-α, CHS, ATP6 and two microsatellite loci, reflected genetic uniformity. The two polymorphic molecular markers resolved six haplotypes among isolates from Indonesia and only a single haplotype elsewhere in Asia. The low diversity observed among isolates in the region of the first outbreak is as expected for a small founder population. The spread of a single clone over large distances throughout the region supports the hypothesis of spread via the human-mediated movement of germplasm.

Keywords:  Plants for planting . Nursery trade . DNA, sequence . Founder effect . Microsatellites, Germplasm movement

 

By Dr Paul Barber, Director of ArborCarbon

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Dr Paul Barber
About the Author
Paul is the Director of ArborCarbon and holds the position of Adjunct Associate Professor at Murdoch University where he continues to mentor students and is actively involved in research aimed at sustainable vegetation management outcomes. Please find more information in his CV- [pdf, 380kB]