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Various hypotheses have been proposed regarding the origin of the plant pathogen Phytophthora cinnamomi. P. cinnamomi is a devastating, highly invasive soilborne pathogen associated with epidemics of agricultural, horticultural and forest plantations and native ecosystems worldwide. We conducted a phylogeographic analysis of populations of this pathogen sampled in Asia, Australia, Europe, southern and northern Africa, South America, and North America. Based on genotyping-by-sequencing, we observed the highest genotypic diversity in Taiwan and Vietnam, followed by Australia and South Africa. Mating type ratios were in equal proportions in Asia as expected for a sexual population. Simulations based on the index of association suggest a partially sexual, semi-clonal mode of reproduction for the Taiwanese and Vietnamese populations while populations outside of Asia are clonal. Ancestral area reconstruction provides new evidence supporting Taiwan as the ancestral area, given our sample, indicating that this region might be near or at the centre of origin for this pathogen as speculated previously. The Australian and South African populations appear to be a secondary centre of diversity following migration from Taiwan or Vietnam. Our work also identified two panglobal, clonal lineages PcG1-A2 and PcG2-A2 of A2 mating type found on all continents. Further surveys of natural forests across Southeast Asia are needed to definitively locate the actual centre of origin of this important plant pathogen. Agricultural Research Service, Grant/Award Number: 2072-22000-041-00-D; National Institute of Food and Agriculture, Grant/Award Number: 2011-68004-30154 and 2018-67013-27823 info:eu-repo/semantics/publishedVersion

Globally, Phytophthora cinnamomi is listed as one of the 100 worst invasive alien species and active management is required to reduce impact and prevent spread in both horticulture and natural ecosystems. Conversely, there are regions thought to be suitable for the pathogen where no disease is observed. We developed a climex model for the global distribution of P. cinnamomi based on the pathogen's response to temperature and moisture and by incorporating extensive empirical evidence on the presence and absence of the pathogen. The climex model captured areas of climatic suitability where P. cinnamomi occurs that is congruent with all available records. The model was validated by the collection of soil samples from asymptomatic vegetation in areas projected to be suitable by the model for which there were few records. DNA was extracted, and the presence or absence of P. cinnamomi was determined by high-throughput sequencing (HTS). While not detected using traditional isolation methods, HTS detected P. cinnamomi at higher elevations in eastern Australia and central Tasmania as projected by the climex model. Further support for the climex model was obtained using the large data set from south-west Australia where the proportion of positive records in an area is related to the Ecoclimatic Index value for the same area. We provide for the first time a comprehensive global map of the current P. cinnamomi distribution, an improved climex model of the distribution, and a projection to 2080 of the distribution with predicted climate change. This information provides the basis for more detailed regional-scale modelling and supports risk assessment for governments to plan management of this important soil-borne plant pathogen.

Diversity within and between Cryptodiaporthe melanocraspeda populations on Banksia spp. and variation in susceptibility within B. coccinea that resulted from pathogen-induced selection, was investigated. Genetic distances between C. melanocraspeda isolate populations were much less than those between Cryptodiaporthe spp. Spore size and rates of lesion extension of isolate populations of C. melanocraspeda formed continua that reflected intraspecific variation within a species. There were two isozyme groups amongst the populations of C. melanocraspeda from different Banksia hosts. Populations of C. melanocraspeda from the five geographic clusters could be divided into three geographic isozyme groups. Pycnidiospore size of populations of C. melanocraspeda isolates from different Banksia hosts formed a continuum from relatively short-thin spores for isolates from B. sessilis and relatively long-wide spores for isolates from B. baxteri. The rate of lesion extension formed a continuum, with ranking of isolates from slowest to fastest rates differing on the four hosts inoculated. Isolate populations varied in their pattern of adaptation to local Banksia host populations. Although intraspecific variation in the response of B. coccinea to C. melanocraspeda was mainly skewed to highly susceptible trees, there would be the potential for the conservation of diversity through single-tree selection for resistance and breeding.

This study determined spatio-temporal invasion dynamics of Phytophthora cinnamomi, examined differences between disease centres and inferred mechanisms of invasion. Patch disease extension was measured from aerial photographs of three Banksia woodland areas infested with P. cinnamomi. Disease extension was also determined from the fronts of six disease centres in Banksia woodland biomes and a disease front in Eucalyptus marginata forest. A localised, salient, disjunct pattern of spatial variation in upslope disease extension that occurred in all disease centres between years was probably due to growth of P. cinnamomi in major lateral roots and infection of plants by root to root contact. The square root of the area invaded was significantly related to year after first assessment (R 2 = 0.59–0.97). Linear rates of disease extension from baselines with years after first assessment ranged from 0.1 ± 0.07 and 1.46 ± 0.39 m/year. Differences in P. cinnamomi isolation frequency, community structure and measured variables in different soils did not indicate reasons for the variation in rate of invasion between Banksia woodland disease centres. Management options to limit invasion will depend on whether disease extension is the result of unrestricted movement of infectious propagules in overland and subsurface flows, or relatively restricted growth through roots and root to root contact. The hierarchy of factors affecting the invasive success of P. cinnamomi is discussed.

Isolations from diseased plants and controlled inoculations indicate that the host range of the canker pathogen Luteocirrhus shearii is mainly limited to Banksia. Branches exhibiting canker symptoms were sampled from the Geraldton Sandplains, Swan Coastal Plain, Jarrah Forest, Warren and Esperance Sandplains bioregions of the South-West Botanical Province of Western Australia (n = 1,351). Luteocirrhus shearii was isolated from only Proteaceae and did not infect wound inoculated Myrtaceae. The pathogen was isolated from or formed extensive lesions in 15 Banksia species. Differences in isolation frequency and rates of lesion extension of L. shearii between Banksia spp. may indicate different modes of infection by the canker pathogen. By exerting top-down control of population dynamics of Banksia communities from lower trophic levels, L. shearii would substantially alter host species diversity and in turn ecosystem processes. Predicted climate change could influence future biotic reorganisations following L. shearii invasion. What determines the limited host range of L. shearii compared to the community of organisms on Banksia needs to be determined.

Stem injection, high and low-volume aerial spray and stem spray using Pentra-bark® and Pulse® as bark penetrants were compared to determine whether application method could increase the effectiveness of phosphite in inhibiting colonisation by Phytophthora cinnamomi. Phosphite stem injection and stem spray inhibited P. cinnamomi more effectively than aerial application. In contrast, low-volume aerial phosphite spray showed the least effectiveness. Colonisation in B. attenuata was significantly reduced by stem spray of phosphite alone at 400 g/L and phosphite at ≥200 g/L when combined with Pentra-bark® or Pulse®. For B. baxteri, colonisation of P. cinnamomi was significantly reduced by stem spray of phosphite alone at ≥200 g /L and by phosphite ≥100 g /L when combined with Pentra-bark® and phosphite at ≥200 g /L combined with Pulse®. Stem spray did not significantly control of colonisation in L. inermis var. inermis. Only stem injection overcame the ineffectiveness of phosphite application in L. inermis var. inermis previously recorded. Different responses of species to phosphite application highlights the need to assess effectiveness at the species level.

Ex-situ comparison of Phytophthora cinnamomi habitat suitability of soils from a topographic gradient across the Swan Coastal Plain from dunes to a forested peneplain provides clues to the influences of soil type on disease development. Only ex-situ testing was possible to compare P. cinnamomi habitat suitability because of confinement of Swan Coastal Plain plant communities to a relatively few, small remnants. Disease expression was determined in a shadehouse environment and stimulation of sporangium production in a controlled environment. Greater than 90 % mortality of Banksia grandis following P. cinnamomi ex-situ soil inoculation and greatest stimulation of sporangium formation and release of zoospores by soil extracts from Bassendean Dune, Pinjarra Plain, Ridge Hill Shelf and Jarrah Forest reflected high disease incidence and severity that occurs in these landscape elements. In Quindalup Dune (QD) soil there were no deaths of B. grandis following P. cinnamomi soil inoculation, consistent with the lack of disease incidence and expression that occurs in QD plant communities. However QD soils stimulated sporulation similar to the other landscape element soil extracts. Higher levels of phosphorus and calcium in QD soils possibly influenced the host-infection process after sporangium formation and zoospore release. Greater than 90 % plant mortality following P. cinnamomi soil inoculation and stimulation of sporulation by Spearwood Dune (SD) soil extracts did not reflect low disease incidence and severity that occurs in this landscape element. Differences in measured variables between soils did not indicate reasons for the high plant mortality following ex-situ soil inoculation and low disease expression in SD plant communities, possibly due to post sporulation effects of the soil environments on host infection and invasion by P. cinnamomi.

Morphological and DNA sequence characteristics of a pathogenic fungus isolated from branch cankers in Proteaceae of the South West Australian Floristic Region elucidated a new genus and species within Cryphonectriaceae (Diaporthales). The pathogen has been isolated from canker lesions in several Banksia species and Lambertia echinata subsp. citrina, and is associated with a serious decline of the rare B. verticillata. Lack of orange pigment in all observed structures except cirrhi, combined with pulvinate to globose black semi-immersed conidiomata with paraphyses, distinguishes the canker fungus from other genera of Cryphonectriaceae. This was confirmed by DNA sequence analysis of the ITS regions, β-tubulin, and LSU genes. The fungus (sexual morph unknown) is described as Luteocirrhus shearii gen. sp. nov. Lesions in seedlings of Banksia spp. following wound inoculation and subsequent recovery confirm Koch’s postulates for pathogenicity. This pathogen of native Proteaceae is currently an emerging threat, particularly toward B. baxteri and B. verticillata.

Determination of susceptibility to Phytophthora cinnamomi affirms the exceptional broad host range of the pathogen and diversity of host–pathogen interactions in the native flora of the South-West Botanical Province of Western Australia. Positioning taxa on the P. cinnamomi resistance-susceptibility continuum prioritises taxa in relation to the threat posed by the pathogen. Variation in susceptibility of 501 Western Australian plant taxa to P. cinnamomi infection was evaluated after soil inoculation. Disease progress curves following soil inoculation were analysed with the three logistic model parameters of upper asymptote (Kmax), lag time (t½K) and intrinsic rate of increase (r). The susceptibility continuum represented by the ordination of parameters of the logistic model for % plant mortality in two dimensions was similar for threatened, priority and common taxa. Variation in parameters of the logistic model decreased with susceptibility. Although resistant taxa had low Kmax, the values for delay and rate varied. In comparison, susceptible taxa tended to have high Kmax short delay and fast rate. Most of the taxa in Fabaceae, Malvaceae, Myrtaceae and Poaceae tested were resistant to P. cinnamomi. A few taxa in Fabaceae and Myrtaceae (18 and 10 %, respectively) were susceptible to the pathogen. Casuarinaceae were mainly resistant, but showed a range of responses to P. cinnamomi. Ericaceae were mainly susceptible. Proteaceae showed a broad range of responses from resistant to susceptible. Significantly greater resistance of sprouters than seeders and the significant negative relationship between mortality and leaf phenolics, may be examples of resistance mechanisms through fortuitous side effects of ecological fitting of functional traits that evolved in response to different sets of biotic and abiotic conditions that occurred before the introduction of P. cinnamomi. Identification of resistant individuals in threatened taxa would ensure survival of taxa and conservation of genetic diversity.

Novel species of fungi described in this study include those from various countries as follows: Australia: Banksiophoma australiensis (incl. Banksiophoma gen. nov.) on Banksia coccinea, Davidiellomyces australiensis (incl. Davidiellomyces gen. nov.) on Cyperaceae, Didymocyrtis banksiae on Banksia sessilis var. cygnorum, Disculoides calophyllae on Corymbia calophylla, Harknessia banksiae on Banksia sessilis, Harknessia banksiae-repens on Banksia repens, Harknessia banksiigena on Banksia sessilis var. cygnorum, Harknessia communis on Podocarpus sp., Harknessia platyphyllae on Eucalyptus platyphylla, Myrtacremonium eucalypti (incl. Myrtacremonium gen. nov.) on Eucalyptus globulus, Myrtapenidiella balenae on Eucalyptus sp., Myrtapenidiella eucalyptigena on Eucalyptus sp., Myrtapenidiella pleurocarpae on Eucalyptus pleurocarpa, Paraconiothyrium hakeae on Hakea sp., Paraphaeosphaeria xanthorrhoeae on Xanthorrhoea sp., Parateratosphaeria stirlingiae on Stirlingia sp., Perthomyces podocarpi (incl. Perthomyces gen. nov.) on Podocarpus sp., Readeriella ellipsoidea on Eucalyptus sp., Rosellinia australiensis on Banksia grandis, Tiarosporella corymbiae on Corymbia calophylla, Verrucoconiothyrium eucalyptigenum on Eucalyptus sp., Zasmidium commune on Xanthorrhoea sp., and Zasmidium podocarpi on Podocarpus sp. Brazil: Cyathus aurantogriseocarpus on decaying wood, Perenniporia brasiliensis on decayed wood, Perenniporia paraguyanensis on decayed wood, and Pseudocercospora leandrae-fragilis on Leandra fragilis. Chile: Phialocephala cladophialophoroides on human toe nail. Costa Rica: Psathyrella striatoannulata from soil. Czech Republic: Myotisia cremea (incl. Myotisia gen. nov.) on bat droppings. Ecuador: Humidicutis dictiocephala from soil, Hygrocybe macrosiparia from soil, Hygrocybe sangayensis from soil, and Polycephalomyces onorei on stem of Etlingera sp. France: Westerdykella centenaria from soil. Hungary: Tuber magentipunctatum from soil. India: Ganoderma mizoramense on decaying wood, Hodophilus indicus from soil, Keratinophyton turgidum in soil, and Russula arunii on Pterigota alata. Italy: Rhodocybe matesina from soil. Malaysia: Apoharknessia eucalyptorum, Harknessia malayensis, Harknessia pellitae, and Peyronellaea eucalypti on Eucalyptus pellita, Lectera capsici on Capsicum annuum, and Wallrothiella gmelinae on Gmelina arborea. Morocco: Neocordana musigena on Musa sp. New Zealand: Candida rongomai-pounamu on agaric mushroom surface, Candida vespimorsuum on cup fungus surface, Cylindrocladiella vitis on Vitis vinifera, Foliocryphia eucalyptorum on Eucalyptus sp., Ramularia vacciniicola on Vaccinium sp., and Rhodotorula ngohengohe on bird feather surface. Poland: Tolypocladium fumosum on a caterpillar case of unidentified Lepidoptera. Russia: Pholiotina longistipitata among moss. Spain: Coprinopsis pseudomarcescibilis from soil, Eremiomyces innocentii from soil, Gyroporus pseudocyanescens in humus, Inocybe parvicystis in humus, and Penicillium parvofructum from soil. Unknown origin: Paraphoma rhaphiolepidis on Rhaphiolepsis indica. USA: Acidiella americana from wall of a cooling tower, Neodactylaria obpyriformis (incl. Neodactylaria gen. nov.) from human bronchoalveolar lavage, and Saksenaea loutrophoriformis from human eye. Vietnam: Phytophthora mekongensis from Citrus grandis, and Phytophthora prodigiosa from Citrus grandis. Morphological and culture characteristics along with DNA barcodes are provided.

Variation in susceptibility of 109 Western Australian Banksia and Dryandra and 16 Eastern Australian Banksia to Phytophthora cinnamomi infection was evaluated after soil inoculation. Banksia and Dryandra were initially analysed separately and then combined due to the transfer of Dryandra to Banksia. Disease progress curves of % mortality following soil inoculation were analysed with the three logistic model parameters of upper asymptote (Kmax), lag time (t½K) and intrinsic rate of increase (r). The susceptibility continuum represented by the ordination of parameters of the logistic model for % plant mortality in two dimensions was similar for Banksia, Dryandra and combined Banksia and Dryandra. Although resistant taxa had low Kmax, the values for delay and rate varied. In comparison, susceptible taxa tended to have high Kmax short delay and fast rate. Western Australian threatened and priority Banksia were significantly more susceptible than common Banksia. Seeders were more susceptible than resprouters. There was no significant difference in Western Australian Banksia susceptibility between soil, rainfall region, bioregion and growth form. Of the Western Australian Banksia tested, 40 % were most at risk of P. cinnamomi infection because they were either threatened, priority or common though geographically restricted taxa with Kmax of mortality >50 %. Positioning Banksia taxa on the P. cinnamomi resistance-susceptibility continuum needs to be incorporated into extinction-risk methodology in order to prioritise flora for conservation actions according to hazard from the pathogen.

Relationships were examined between visible necrotic lesion and colonisation following stem wound inoculated of native plant species of the South-West Botanical Province of Western Australia with Phytophthora cinnamomi. Relationships were determined over a wide range of biotic and abiotic environments of plant taxa, host susceptibility, isolate, phosphite fungicide spray, native community and glasshouse environments, seasons and soil types. Consistent significant relationships were found between necrotic lesions and colonisation over the different environments. Visible necrotic lesions were either in-phase with or greater than colonisation in 55 % of the environments analysed. ANCOVA interactions of total visible necrotic lesion with treatments were not significant for 10 out of 14 interactions, indicating homogeneity of slopes in the majority of cases. Rather than having distinct hemibiotrophic stages, P. cinnamomi switches between necrotic lesions and colonisation of symptomless tissue depending on environmental conditions. Average necrotic lesion/taxa in stems following wound inoculation was significantly positively correlated with mortality following soil inoculation. Determination of visible necrotic lesion was 10 times quicker and 30 times cheaper than colonisation, giving considerable savings for large experiments. Quantification of necrotic lesion-colonisation relationships aids determination of mechanisms of pathogen invasion and host resistance.

Pathogen mediated changes in vegetation cover were determined from variation of ground cover and canopy closure between diseased and adjoining healthy areas of Banksia shrubland, Banksia woodland and Eucalyptus marginata forest biomes invaded by Phytophthora cinnamomi. For healthy areas, ground cover tended to be greatest in the relatively low rainfall areas where canopy closure was the least. Ground cover significantly decreased, but canopy closure significantly increased with plant height in healthy areas. Disease caused by P. cinnamomi resulted in a mean decrease in ground cover of ~28% for infested woodland and forest biomes. This decrease was significantly greater than the mean decrease in ground cover of 14% for shrubland biomes. In contrast disease decreased mean canopy closure in shrubland biomes by 32% which was significantly greater than the decrease of ~22% for diseased woodland and forest biomes. Re-establishment of vegetation cover using resistant selections of local dominant plant species may substantially return to infested areas the functionality of healthy areas.

Variation between plant species of in-planta concentration and effectiveness of low-volume phosphite spray on lesion development of Phytophthora cinnamomi was determined for 14 species in two native communities of the South-West Botanical Province of Western Australia and 10 species in a glasshouse environment. There was considerable variation in stem phosphite concentrations between environments, phosphite treatment and taxa following low-volume spray. Average stem phosphite concentrations for taxa in the glasshouse environment were 8-fold greater than those in natural environments. In 48% of taxa, phosphite concentrations in stems of plants sprayed with 48 kg phosphite/ha were significantly greater than that for plants sprayed with 24 kg phosphite/ha. There was a 22 to 28-fold difference in stem tissue phosphite concentrations between taxa in the native communities and a 31 to 63-fold difference between taxa in the glasshouse environment. Phosphite was effective in 46% of the taxa based on rate of visible lesion development being significantly less in plants sprayed with 24 or 48 kg phosphite/ha than plants not sprayed. There were significant linear relationships between in-planta phosphite concentration and lesion development. Variation in phosphite effectiveness can be extended into a general hypothesis that plant species may differ in species-specific in-planta phosphite concentration thresholds that must be exceeded before effective control of P. cinnamomi can be achieved. Databases of species falling into phosphite effective or not effective groups can be used to assess variation in phosphite effectiveness between different threatened communities and assist in the development of application procedures aimed at overcoming ineffectiveness of the fungicide.

Soil and stem wound inoculation was used to determine variation in phosphite efficacy for the control of Phytophthora cinnamomi within the genus Lambertia. Disease progress curves following soil inoculation with P. cinnamomi were analysed with the parameters of the logistic model. The asymptote and lag logistic model parameters of disease progress better differentiated between phosphite treatments than the rate parameter. Low-volume phosphite spray significantly reduced the asymptote Kmax of % mortality and significantly increased the delay t1/2K for all Lambertia taxa soil inoculated. Kmax was significantly negatively correlated with delay t1/2K and taxa sprayed with 48 kg phosphite/ha had a lower Kmax and longer delay t1/2K than taxa not sprayed. Phosphite significantly reduced colonisation by P. cinnamomi in stems of 19% of Lambertia taxa tested. The differences in phosphite efficacy between soil and wound inoculation suggests that phosphite may inhibit the infection process more than post-infection stem colonisation. The lack of direct relationships between control of P. cinnamomi and tissue phosphite concentrations may be related to different effective phosphite thresholds between taxa. Time-course studies of in-planta phosphite concentrations in relation to effective control of P. cinnamomi are required in different plant species and environments.

Habitat suitability for P. cinnamomi was com- pared between soils from the major soil groups of the Fitzgerald River National Park. Because of the mainly disease-free status of the National Park, only ex-situ testing was possible by Gradsect sampling of soils on a topo- graphic gradient and determining the influence on disease expression in a shadehouse environment and stimulation of sporangium production in a controlled environment. The upper asymptote (Kmax), lag time (t½K) and intrinsic rate of increase (r) of the logistic model were calculated from disease progress curves of Banksia baxteri plants following soil inoculation with P. cinnamomi and sporulation curves. The Qualinup Sands and the Dry Phase of the Nyerilup Sand had the greatest % mortality Kmax values and the Perkins and Red Loams had the least. For B. baxteri mortality, delay significantly increased and rate decreased along a fertility gradient from relatively infertile sands to fertile loams. Kmax of total number of sporangia/mm 2 of mycelium for winter collected soils was significantly linearly positively correlated with Kmax of germinating spores/disc and negatively correlated with rate of mortality of B. baxteri. The loams with the slowest rate of mortality of B. baxteri stimulated the most sporulation. Habitat suitability of the major soil groups of the landscape matrix of the Fitzgerald River National Park for P. cinnamomi can be used to predict risk of invasion and hazard in healthy areas and prioritise areas of greatest risk of invasion and conservation consequences from hazard.

The introduction and subsequent impact of Phytophthora cinnamomi within native vegetation is one of the major conservation issues for biodiversity in Australia. Recently, many new Phytophthora species have been described from Australia’s native ecosystems; however, their distribution, origin, and potential impact remain unknown. Historical bias in Phytophthora detection has been towards sites showing symptoms of disease, and traditional isolation methods show variable effectiveness of detecting different Phytophthora species. However, we now have at our disposal new techniques based on the sampling of environmental DNA and metabarcoding through the use of high-throughput sequencing. Here, we report on the diversity and distribution of Phytophthora in Australia using metabarcoding of 640 soil samples and we compare the diversity detected using this technique with that available in curated databases. Phytophthora was detected in 65% of sites, and phylogenetic analysis revealed 68 distinct Phytophthora phylotypes. Of these, 21 were identified as potentially unique taxa and 25 were new detections in natural areas and/or new introductions to Australia. There are 66 Phytophthora taxa listed in Australian databases, 43 of which were also detected in this metabarcoding study. This study revealed high Phytophthora richness within native vegetation and the additional records provide a valuable baseline resource for future studies. Many of the Phytophthora species now uncovered in Australia’s native ecosystems are newly described and until more is known we need to be cautious with regard to the spread and conservation management of these new species in Australia’s unique ecosystems.

Variation in susceptibility to Phytophthora cinnamomi Rands infection within the genus Lambertia Sm. was evaluated by soil and stem inoculation. Disease-progress curves following soil inoculation were analysed with the three logistic-model parameters of upper asymptote (K max), lag time (t 1/2K ) and intrinsic rate of increase (r), which were combined into a mortality score. Resistant Lambertia taxa had the lowest K max, longest t 1/2K and slowest r. These parameters change to greatest K max, shortest t 1/2K and fastest r for susceptible Lambertia taxa. Mortality score following soil inoculation was significantly positively correlated with lesion score determined by stem inoculation. The plot of the scores ranked the Lambertia taxa in relation to P. cinnamomi susceptibility on the resistance–susceptibility continuum and prioritised taxa in relation to the threat posed by the pathogen. The highest mortality and lesion scores for the threatened rare and endangered taxa L. orbifolia subsp. orbifolia, L. fairallii and L. rariflora subsp. lutea suggest a high risk of extinction from P. cinnamomi infestation. Furthermore, rare and endangered taxa L. orbifolia subsp. Scott River Plains, L. echinata subsp. occidentalis and L. echinata subsp. echinata that have high mortality and moderate lesion scores are also likely to be at high risk of extinction from P. cinnamomi infestation. Among common taxa with restricted geographic distribution, L. ericifolia has high mortality and lesion scores, suggesting a high risk of localised extinction and loss of genetic diversity in P. cinnamomi disease centres. Positioning taxa on the P. cinnamomi resistance–susceptibility continuum needs to be incorporated into extinction-risk methodology so as to prioritise flora for conservation actions according to hazard from the pathogen.

The influence of site on effectiveness of low-volume spray of phosphite for the control of Phytophthora cinnamomi was compared between sites differing in soil nutrient status. The sites ranged from infertile deep grey sands to a red loam in the Esperance Plains bioregion, and infertile gravelly sand of the Havel site-vegetation type P to a red loam of Havel site-vegetation typeQin the northern Jarrah Forest bioregion. Following low-volume spray of 0, 24 or 48 kg phosphite/ha, phosphite effectiveness was determined from assessment of rate of colonisation and inhibition of stem colonisation by P. cinnamomi, and stem phosphite concentration in challenge inoculation stems of Lambertia inermis var. inermis in Esperance Plains bioregion sites and Banksia grandis in Jarrah Forest bioregion sites. Phosphite effectiveness was mainly influenced by plant species rather than site. Phosphite spray significantly controlled P. cinnamomi colonisation in B. grandis, but not in L. inermis var. inermis. Site had no consistent influence on the effect of phosphite on P. cinnamomi despite large differences in soil nutrient status between sites. Differences between sites and site ranking changed with inoculation time and rate of phosphite spray, and duplicate sites differed significantly from each other. Site, rate of phosphite spray, time after spray and plant species significantly affected stem phosphite concentrations. In both Esperance Plains bioregion and Jarrah Forest bioregion sites, stem phosphite concentrations were greatest in fertile loam sites and least in infertile sand or gravelly sand sites. Stem phosphite concentrations increased with rate of phosphite spray with concentrations in stems receiving 48 kg phosphite/ha being 1.2 to 3-times-greater than that in stem sprayed with 24 kg phosphite/ha. Six months after low-volume spray, phosphite concentrations in L. inermis var. inermis stems had declined for all sites and spray rates to only 4–17% of original concentrations. Decline of phosphite concentrations in B. grandis stems was slower than that for L. inermis var. inermis stems. The results indicate that effectiveness of phosphite against P. cinnamomi infection in different communities will depend more on plant species composition than soil nutrient status. Differences in phosphite effectiveness between plant species may be related to differences in phosphite concentration thresholds yet to be quantified, above which tissue concentrations must be achieved before inhibition of P. cinnamomi colonisation occurs. In rapid colonisation/phosphite low-responsive species such as L. inermis var. inermis, the threshold may be greater than that required for a response in a rapid colonisation/phosphite high-response species such as B. grandis. These results demonstrate the need to determine thresholds for individual plant species and in different environments.

Changes in plant species richness and composition, vegetation structure, ecosystem functioning and soil nutrients following invasion of Banksia woodland and Eucalyptus marginata forest biomes by the introduced soilborne multihost plant pathogen Phytophthora cinnamom were determined using space-for-time substitution of diseased and adjoining healthy areas. In most study areas, canopy closure, basal area and number of plant species were significantly lower in old diseased compared with adjoining healthy areas, with diseased front intermediate between the two. In half of the study areas, percentage ground cover and total plant species cover were significantly lower in old diseased compared with adjoining healthy areas, with diseased front intermediate between the two. Evenness, Shannon-Weiner H and Simpson’s D did not significantly change between disease status for the majority of study areas. For ordination of percentage canopy closure and ground cover there was separation of study areas along a disease status gradient and a weak soil fertility gradient. There was significantly less percentage organic carbon, extractable phosphorus and extractable and total potassium in old diseased areas compared with adjoining healthy areas for one-quarter to a third of the study areas. Total phosphorus changed significantly between disease status, but this was due to higher levels in diseased front compared with the old diseased or adjoining healthy areas. For all study areas there was no significant effect of disease status on percentage total nitrogen and pH. The cover of a majority of plant species did not change significantly between disease status with 16% of the total number of perennial species in healthy areas significantly decreasing and 10% significantly increasing in cover in old diseased compared with adjoining healthy areas. As with significant differences in cover between disease status, change in cover of a majority of plant species was not significantly correlated with canopy closure. Cover of 20% of the total number of perennial species in healthy areas was significantly linearly positively correlated with canopy closure and the cover of 10% of plant species was significantly negatively correlated with canopy closure. These species were herbs and shrubs from a range of families with a mixture of functional properties such as Phytophthoria cinnamomi susceptibility, response to fire, rooting type and mycorrhizal association. The paper concludes with a conceptual analysis of core issues and those that cascade out of core issues involved in pathogen and patch plant community interactions.

A risk-assessment tool was used to investigate the risk of extinction from disease caused by Phytophthora cinnamomi to 33 taxa from the Stirling Range National Park, Western Australia. Criteria used to score risk of extinction were the direct impact of P. cinnamomi on taxa, number of extant or extinct populations, percentage of populations infested by P. cinnamomi, proximity and topographical relationship of populations to P. cinnamomi, proximity of populations to tracks and the number of additional threatening processes. Direct impact scores were derived from mortality curves determined from the survival of taxa after soil inoculation with P. cinnamomi in a shade-house environment. On the basis of the total extinction risk score, nine taxa had a ‘very high’, five had a ‘high’, six a ‘moderate’, eight a ‘low’, four a ‘very low’ and one ‘no’ risk of extinction. Whereas the methodology confirmed the current threatened status of nine taxa, it also identified five taxa, not currently listed, to be at ‘high’ risk of extinction. Other threatening processes identified included fire, herbivory, aerial canker disease and climate change. These combine with P. cinnamomi to push taxa further towards extinction. Quantification of risk of extinction identifies taxa at risk and allows for prioritisation of management actions for currently threatened flora. This risk-assessment methodology combined glasshouse inoculation with habitat and ecological data, current in situ disease impact and proximity to disease and vectors, to enable a more comprehensive assessment of extinction risk and may be used in other areas with endemic flora threatened by P. cinnamomi.

Estimates of canopy closure using hemispherical digital images, canopy cover using a point-intercept method, ground cover, number of plant species and total plant species cover were used to quantify the impact of Phytophthora cinnamomi in disease centres in Banksia shrubland, Banksia woodland and Eucalyptus marginata forest biomes of the South-West Botanical Province of Western Australia. Estimates of the time required to capture and analyse data and correlations were used to contrast the five methods. For canopy closure or cover, hemispherical digital images were on average, seven times faster to capture and analyse than the point-intercept method. For both canopy closure and ground cover, mean values from three point samples were not significantly different to mean values from transects across the disease front. Differences in canopy closure and ground cover between biomes and disease obtained from point sampling showed the same trends as transects. Canopy closure differed significantly between biome, being greatest for E. marginata forest, least for Banksia shrubland and intermediate for Banksia woodland. Ground cover was greatest for Banksia shrubland, least for E. marginata forest and intermediate for Banksia woodland. For all biomes there was significantly less canopy closure in diseased than adjoining healthy areas. There was no significant difference in ground cover between diseased and adjoining healthy areas of Banksia shrubland, but significantly less ground cover in diseased than adjoining healthy areas in the Banksia woodland and E. marginata forest. Canopy closure and ground cover are likely measuring different aspects of the impact of P. cinnamomi and, therefore, both should be measured when determining pathogen-mediated changes. Advantages of using hemispherical digital images over the other methods for determining temporal and spatial changes associated with P. cinnamomi infestation are discussed.

Disease progress curves were evaluated for the assessment of the susceptibility of the flora of the South-West Botanical Province of Western Australia threatened by Phytophthora cinnamomi infection. Disease progress was analysed with the logistic model because this model describes numerous observed disease progress curves. In addition, the three logistic model parameters, upper asymptote (Kmax), lag time (t1/2K) and intrinsic rate of increase (r), have rational physical interpretations. Because the logistic model parameters for percentage of plants with collar lesions were significantly related to parameters for percentage mortality, only the logistic model parameters for percentage mortality were used in subsequent analysis. Susceptible hosts had the greatest Kmax, shortest t1/2K and fastest r. These parameters change to lowest Kmax, longest t1/2K and slowest r for resistant plant taxa. There was a greater change of Kmax with t1/2K than with r. The Kmax and r parameters did not differ significantly between isolates of the pathogen. Variation in mortality curve parameters between years was greater for Banksia grandis than for the more susceptible B. brownii. There was no significant linear relationship between mortality curve parameters for B. brownii and temperature variables. For B. grandis there were four significant linear relationships between a mortality curve parameter and a temperature variable. Potting mix soil favoured greatest disease progress with the shortest t1/2K and fastest r. Susceptibility to P. cinnamomi determined in a shadehouse environment following soil inoculation was significantly positively correlated with susceptibility recorded in disease centres in natural environments.

The invasive soilborne plant pathogen Phytophthora cinnamomi Rands is a major threatening process in the South-west Botanical Province of Western Australia, an internationally recognised biodiversity hotspot. Comparatively recent introduction of P. cinnamomi into native plant communities of the South-west Botanical Province of Western Australia since the early 1900s has caused great irreversible damage and altered successional change to a wide range of unique, diverse and mainly susceptible plant communities. The cost of P. cinnamomi infestation to community values is illustrated by examination of direct (mortality curves, changes in vegetation cover) and indirect impacts on biodiversity and ecosystem dynamics, the proportion of Threatened Ecological Communities infested, Declared Rare Flora either directly or indirectly threatened by infestation and estimates of the proportion of the native flora of the South-west Botanical Province susceptible to the pathogen. While direct impacts of P. cinnamomi have been poorly documented in the South-west Botanical Province, even less attention has been given to indirect impact where destruction of the habitat by the pathogen affects taxa not directly affected by infection. Current poor understanding and quantification of indirect impacts of P. cinnamomi through habitat destruction results in an underestimation of the true impact of the pathogen on the flora of the South-west Botanical Province. Considerable variation of susceptibility to P. cinnamomi among and within families of threatened flora and responses of taxa within the genus Lambertia show how classification within family and genus are poor predictors of species susceptibility. Within apparently susceptible plant species, individuals are resistant to P. cinnamomi infection. Intra-specific variation in susceptibility can be utilised in the long-term management of threatened flora populations and needs to be a high research priority. Current control strategies for conservation of flora threatened by P. cinnamomi integrate hygiene and ex situ conservation with disease control using fungicide. Application of the fungicide phosphite has proven effective in slowing progress of P. cinnamomi in infested, threatened communities. However, variation in plant species responses to phosphite application is a major factor influencing effective control of P. cinnamomi in native communities. A greater understanding of the mechanisms of action of phosphite in plant species showing different responses to the fungicide may provide options for prescription modification to increase phosphite effectiveness in a range of plant species. The range of responses to P. cinnamomi infection and phosphite application described for Lambertia taxa suggests that the genus would make an ideal model system to elucidate the mechanisms of resistance to P. cinnamomi and the effectiveness of phosphite against the pathogen.

This study compares, for the first time, variation in estimates of susceptibility of native flora to Phytophthora cinnamomi Rands among four databases and proposes an estimate of the proportion of the flora of the South-West Botanical Province of Western Australia that is susceptible to the pathogen. Estimates of the susceptibility of south-western native flora to P. cinnamomi infection were obtained from databases for Banksia woodland of the Swan Coastal Plain, jarrah (Eucalyptus marginata Donn. ex Smith) forest, the Stirling Range National Park and Rare and Threatened Flora of Western Australia. For the woodland, forest and national park databases, hosts were naturally infected in uncontrolled diverse natural environments. In contrast, threatened flora were artificially inoculated in a shadehouse environment. Considerable variation occurred within taxonomic units, making occurrence within family and genus poor predictors of species susceptibility. Identification of intra-specific resistance suggests that P. cinnamomi could be having a strong selection pressure on some threatened flora at infested sites and the populations could shift to more resistant types. Similar estimates of the proportion of species susceptible to P. cinnamomi among the databases from the wide range of environments suggests that a realistic estimate of species susceptibility to P. cinnamomi infection in the south-western region has been obtained. The mean of 40% susceptible and 14% highly susceptible equates to 2284 and 800 species of the 5710 described plant species in the South-West Botanical Province susceptible and highly susceptible to P. cinnamomi, respectively. Such estimates are important for determining the cost of disease to conservation values and for prioritising disease importance and research priorities. P. cinnamomi in south-western Australia is an unparalleled example of an introduced pathogen with a wide host range causing immense irreversible damage to unique, diverse but mainly susceptible plant communities.

We determined the effect of phosphite application as a high-volume spray to the understorey, and injection of overstorey species, on disease front extension and rate of extension of Phytophthora cinnamomi in Banksia woodland. Burning of the trial site by the owner gave an unplanned effect of fire on phosphite treatment. The five phosphite treatments were no phosphite (treatment 1), all trees injected with 50 g/L phosphite and the understorey sprayed with 2 g/L phosphite once or twice (treatments 2 and 3, respectively); or all trees injected with 50 g/L phosphite and the understorey sprayed with 5 g/L phosphite once or twice (treatments 4 and 5, respectively). The first phosphite spray occurred in summer (mid-February) 1993, the second spray was 6 weeks later, in April 1993. Overstorey trees of Banksia attenuata, B. ilicifolia and B. menziesii were injected with 50 g/L phosphite the next day after the first spray treatments. The first assessment of the disease front position occurred 0.5 year after the first spray, assessment 2 occurred 4.3 years after the first spray and 3.2 years after the fire and assessment 3, 5.3 years after the first spray and 4.1 years after the fire. Phosphite treatment significantly reduced disease front extension by an average of 0.9 ± 0.1 m, 4.0 ± 0.2 m and 4.1 ± 0.2 m, for assessments 1, 2 and 3, respectively. There were no consistent significant differences in disease front extension between phosphite treatments 2–5. Rates of extension 1 and 2 (calculated between assessments 2 and 1, and 3 and 1, respectively) were reduced by a half to a third by phosphite treatment. There were no consistent significant differences in rate of disease front extension between phosphite treatments 2–5. Residual action of phosphite would not be expected to last in understorey vegetation destroyed by fire, but probably persisted after the fire in the woody roots of injected overstorey trees. This study indicates that injection of overstorey should accompany spray of foliage to ensure long lasting protection by phosphite.

Estimates of the susceptibility of plant species of coastal dune vegetation tokilling by Armillaria luteobubalina Watling & Kilewere obtained from the occurrence of mycelial sheaths of the pathogen beneaththe bark of the root collars of dead plants in 62 disease centres.Dicotyledons (Magnoliopsida) outnumbered monocotyledons (Liliopsida), being81% of the 330 plant species found in disease centres in coastalvegetation. Fifty-one percent of the species were from five Magnoliopsidafamilies with the largest number of species from the Myrtaceae and Proteaceae.Eleven percent of the species were from three Liliopsida families with thelargest number of species from the Cyperaceae. Thirty-four percent of speciesoccurred in three or more disease centres. Thirty-eight percent, or a total of125 of all species, were killed by A. luteobubalina incoastal vegetation. Hosts on which the pathogen did not reach the root collarwould not have been detected. The largest number of species killed were fromthe Proteaceae (26% of species killed) followed by Myrtaceae,Epacridaceae, Papilionaceae and Mimosaceae. Only 6% of species killedwere from the Liliopsida. The distribution of species frequency and thosekilled by infection is positively skewed, with 40% of species notkilled in any centre and 8% killed in greater than 75% of thecentres in which they occurred. The percentage of disease centres in which aspecies occurred and was killed by A. luteobubalina issignificantly linearly correlated with mortality rating and relativeimportance. Cross-tabulation of species by disease centres in which plantswere killed provided the opportunity to classify the relative susceptibilityof plant species to killing by A. luteobubalina.

Sixty-two Armillaria luteobubalina Watling & Kiledisease centres were assessed along the coast from near Cervantes, 160 kmnorth-west of Perth, to Cape Arid, 120 km east of Esperance. Disease centresranged from 0.02 to 6.5 ha in size (mean ± s.e., 1.7 ± 0.2 ha).Most disease centres were active, with mainly old deaths occurring in only7% of centres. Impact was low in only 3% of centres. Diseasecentres mainly occurred on calcareous sands of Holocene dune systems.Susceptible hosts from the Proteaceae, Mimosaceae and Myrtaceae tended to bedominant small trees or shrubs and their death resulted in centres composedmainly of sedges or small shrubs and ground-cover species from a range offamilies. Percentage cover of susceptible plant species was significantly lessin disease centres than adjacent healthy areas. Cover of resistant speciestended to be greater in disease centres than adjacent healthy areas, althoughdifferences were not significant. In association with changes in communitystructure, infection resulted in more bare ground in disease centres thanamongst healthy vegetation. Infection had minimal effect on species richness.The mortality progress curve for the susceptible speciesDryandra sessilis (Knight) Domin increased at a meanapparent infection rate of 0.31 ± s.e. 0.12year-1. A disease centre extended at the rate of 0.004ha year-1 between 1964 and 1983 and 0.07 hayear-1 during the period 1981–1989. Diseaseextension per year was not correlated with yearly rainfall. Threatened taxakilled by A. luteobubalina included the rare andendangered Banksia brownii Baxter ex R.Br.,B. occidentalis R.Br. subsp.formosa Hopper, andB. verticillata R.Br. This is the first report ofdisease significantly altering the structure and composition of coastalvegetation of south-western Australia.Armillaria luteobubalina is a significant additional,and hitherto unrecognised, selection pressure on coastal dune vegetationcommunities, and an important consideration in their management andconservation.

Sixteen half-sib families of jarrah (Eucalyptus marginata) seedlings were screened for resistance to Phytophthora cinnamomi using soil inoculation and stem inoculation in pot experiments, and soil inoculation in a P. cinnamomi-infested field site. Low mortality following soil inoculation and short lesion lengths following stem inoculation were used as indicators of P. cinnamomi resistance. Resistance levels varied continuously across families from high to low values in all experiments, but family rankings were consistent among experiments. The narrow-sense heritability of the resistance character was high at both family (0.74-0.85) and individual-tree (0.43) levels. The resistance of jarrah to P. cinnamomi is under strong genetic control [...]