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The mechanisms by which Phytophthora cinnamomi zoospores infect inundated, above-ground woody stem tissue are described. Using 4-6- and 18-month-old jarrah seedlings, the infection courts were identified and the invasion of the stems at sites of zoospore cyst binding were described. Stems were inoculated with a suspension of motile zoospores on the green stem/young periderm region. Light microscopy was used to examine penetration at sites of taxis, and fluorescent microscopy was used to examine penetration sites of seedlings with intact periderm. Two main infection courts were identified on stems: the emerging axillary shoot and the region of stem immediately surrounding an axillary shoot, where the periderm was thin or discontinuous. Invasion also occurred at sites where the developing shoot had not yet emerged but was at the stem surface. At these sites the pathogen also directly invaded through the thin-walled phellem of the periderm surrounding the shoot. Zoospores of P. cinnamomi were not attracted to stomata on mature leaves or green stems. Penetration of the epidermal cell layer of the axillary bud leaf primordia was inter- and intra-cellular; growth of hyphae in the periderm surrounding the shoot was intercellular; while in collenchyma it was inter- and intra-cellular, being intercellular between polyphenolic-rich cells. Exposed stem collenchyma was also directly invaded immediately adjacent to the young axillary shoot. Zoospores demonstrated taxis to sites of discontinuous periderm, similar to wounded areas where the outer protective layers of the plant are breached. This study presents the first evidence that P. cinnamomi is capable of intercellular penetration of suberized periderm.

Despite its importance as one of the most notorious, globally distributed, multihost plant pathogens, knowledge on the survival strategy of Phytophthora cinnamomi in seasonally dry climates is limited. Soil and fine roots were collected from the rhizosphere of severely declining or recently dead specimens of 13 woody species at 11 dieback sites and two dieback spots and from healthy specimens of five woody species at four dieback-free sites in native forests, woodlands and heathlands of the south-west of Western Australia (WA). Phytophthora cinnamomi was recovered from 80.4, 78.1 and 100% of tested soil, fine root and soil-debris slurry samples at the 11 dieback sites, in some cases even after 18-month storage under air-dry conditions, but not from the small dieback spots and the healthy sites. Direct isolations from soil-debris slurry showed that P. cinnamomi colonies exclusively originated from fine roots and root fragments not from free propagules in the soil. Microscopic investigation of P. cinnamomi-infected fine and small woody roots and root fragments demonstrated in 68.8, 81.3 and 93.8% of samples from nine woody species the presence of thick-walled oospores, stromata-like hyphal aggregations and intracellular hyphae encased by lignitubers, respectively, while thin-walled putative chlamydospores were found in only 21.2% of samples from five woody species. These findings were confirmed by microscopic examination of fine roots from artificially inoculated young trees of 10 woody species. It is suggested that (i) the main function of chlamydospores is the survival in moderately dry conditions between consecutive rain events and (ii) selfed oospores, hyphal aggregations, and encased hyphae and vesicles in infected root tissue of both host and non-host species are the major long-term survival propagules of P. cinnamomi during the extremely dry summer conditions in WA.

The ability of Phytophthora cinnamomi to survive long dry periods is the key to its persistence in the south-west of Western Australia. It has been proposed that dead Banksia grandis are a significant long-term reservoir for P. cinnamomi inoculum. To test this, 36 healthy B. grandis trees were inoculated in April 1999, and the presence of viable propagules in planta was determined between 2 and 34 months after tree death. By 10 months after inoculation, 75% of the trees had died, with the remaining seven trees dying by 22 months. The pathogen was more commonly recovered from bark than from wood, except from those trees that died at 22 months, and more commonly from above-ground trunks than below-ground trunks and roots until 8 months after plant death. In trees that died 12 months after inoculation, P. cinnamomi was recovered from 60% of trunk and root core samples at 3 months, declining to 33% at 10 months, 5.5% at 12 months and 0.1% at 34 months after tree death. In trees that died at 22 months, P. cinnamomi was recovered from 87% of trunk and root samples 2 months after tree death, decreasing to 0.5% by 33 months. This study suggests that the pathogen does not have a saprotrophic phase within dead B. grandis tissue, and B. grandis is unlikely to be a long-term reservoir for P. cinnamomi. However, the manipulation of the density of B. grandis and the use of fire to facilitate the breakdown of dead Banksia trunks in the Eucalyptus marginata (jarrah) forest may reduce the spread and impact of P. cinnamomi.

To understand the pathway used by Phytophthora cinnamomi Rands to penetrate the bark of jarrah, the present study describes unwounded periderm and rhytidome development. Periderm formation is described from its initiation in 4-week-old seedlings to the formation of rhytidome in saplings. Periderm in young seedlings consists of a single type of phellem, namely thin-walled suberised cells. In older seedlings where multiple layers of periderm have formed, layers of thick-walled lignified phellem cells in compacted bands alternate with thin-walled suberised cells. Rhytidome formation in older lignotuberous seedlings and in sapling jarrah occurs through the isolation of secondary phloem by periderm. The rhytidome consists of expanded and partially disintegrated secondary phloem tissue sandwiched between layers of phellem cells. Localised periderm formation beneath stomata results in the formation of lenticels, which are ephemeral features. Superficial periderms occur at sites of leaf and shoot abscission, and of lateral shoot emergence. Concealed axillary shoots lack cuticle on emergence. As the trees age, the internal production of lignified and suberised periderm and rhytidome results in an impenetrable barrier to invasion by P. cinnamomi. However, external sites including lenticels and leaf and shoot abscission and emergence areas, all provide points of ingress in unwounded stems.

To test the hypothesis that resistance in Phytophthora cinnamomi to control by the fungicide phosphite (phosphonate) would arise in sites with prolonged use of phosphite, 30 P. cinnamomi isolates were collected from a range of sites with different phosphite-use histories, including phosphite-treated and untreated avocado orchards, and phosphite-treated and untreated native vegetation sites. The colonizing ability of these isolates was tested by different inoculation methods against a range of host tissues, treated and untreated with phosphite, including mycelial stem inoculation on clonally propagated Leucadendron sp., mycelial root inoculation of lupin seedlings and zoospore inoculation of Eucalyptus sieberi cotyledons. Isolates from avocado orchards with a long history of phosphite use were, on average, more extensive colonizers of the phosphite-treated Leucadendron sp., lupin seedling roots and Eucalyptus sieberi cotyledons. These isolates did not colonize untreated plant tissue (Leucadendron sp.) more extensively than isolates from sites with no history of phosphite use and no isolates were resistant to control by phosphite. Analysis of all isolates with microsatellite markers revealed the majority were from a single clonal lineage. Selection for decreased sensitivity to phosphite in planta has taken place within asexual clonal lineages of P. cinnamomi in sites with prolonged use of phosphite.

Species richness and species composition of ectomycorrhizal (EM) fungi were compared among rehabilitated mine sites and unmined jarrah forest in southwest Western Australia. Species richness, measured in 50 m × 50 m plots, was high. In the wetter, western region, mean species richness per plot in 16-year-old rehabilitated mine sites (63.7 ± 2.5, n = 3) was similar to that of unmined jarrah forest (63.6 ± 9.6, n = 9). In the drier, eastern region, species richness in 12-year-old rehabilitated mine sites (40.3 ± 2.1, n = 3) approached that of nearby forest (52.4 ± 9.3, n = 9). Species composition was analysed by detrended correspondence analysis. Rehabilitated sites of similar age clustered together in the analysis and species composition was closer to the native jarrah forest in the older rehabilitated plots. In unmined forest, species composition of fungal communities in the wetter, western region was different from communities in the drier, eastern region.

Eucalyptus gomphocephala is a keystone canopy species endemic to a narrow (5-10 km wide) coastal strip approximately 300 km in length in south-west Western Australia. E. gomphocephala is undergoing a significant decline that was first identified as a spot decline in 1994 and now occurs throughout large sections of its remnant distribution within Yalgorup National Park, in some areas resulting in 100% mortality. Multiple factors, including soilborne pathogens, have been identified as possibly contributing to the decline. Less fine roots are associated with trees on declining sites compared to those on healthy sites. Foliar analysis indicates that declining trees have lower concentrations of some micronutrients, including zinc, which uptake is typically impaired by fine feeder root loss. A range of Pythiaceous microorganisms have been isolated from declining roots, including a new isolation of a yet described Phytophthora species. The Phytophthora isolates appear morphologically similar to the Phytophthora citricola holotype although are distinct using molecular analysis of the internal transcribe region. The exact phylogeny of the new Phytophthora isolates is being determined using sequence analysis of other gene regions. These isolates may be contributing to the loss of fine roots. Glasshouse trials are currently underway to determine whether these isolates are indeed pathogenic.

A homothallic Phytophthora, isolated at irregular intervals since the 1980s from Western Australian jarrah (Eucalyptus marginata) forest sites, has been previously misidentified as P. citricola based on morphological characters. Based on rDNA sequencing, it has been shown to be an undescribed species that is provisionally designated ‘Phytophthora sp. WA2’ pending a full description. It has been associated with lower stem lesions and root necrosis on dying 1- to 2-year-old jarrah seedlings growing in rehabilitated open-cut bauxite mine pits.

Plots within a forest site and adjacent rehabilitated mine site were artificially inoculated with Phytophthora cinnamomi (infested stem sections). Phosphite, as KOH neutralised phosphorous acid, was applied as a soil drench at 294, 1168 and 1766 g-1 m,-2 P03 . Survival of P. cinnamomi inoculum was assessed at 10, 20 and 30 d post phosphite treatment, and growth of the pathogen into the soil was assessed at 30 d. The experiment was conducted in early winter and repeated in the spring. In winter, Phytophthora was never recovered from inoculum from plots of either soil type treated at the highest rate. In the spring, P. cinnamomi was recovered from inoculum in all treatments, with the exception of forest soil at the two highest rates of treatment, and was never recovered from soil of either type at the highest rate. After the first harvest, the trend was for increasing rates of recovery of P. cinnamomi in most treatments, including the soil-treatment combinations where P. cinnamomi appeared to have been eliminated. Phosphite drenching suppressed, but did not eliminate, P. cinnamomi. Results of a separate experiment showed that, in both soil types, sorption of a significant proportion of phosphite occurred within hours of application.

The efficacy of basal bark application (BBA) of phosphite to control infection by Phytophthora cinnamomi was compared with established application methods in two field experiments. In Banksia menziesii and B. attenuata, BBA was compared with trunk injection and high volume foliar spray (FS). In Eucalyptus marginata (Jarrah), BBA was compared with trunk injection only. Efficacy of treatments was assessed by measuring colonisation of stems artificially inoculated with P. cinnamomi (in situ for Banksia spp., and in excised stems for E. marginata). FS treatment was most effective in reducing colonisation by P. cinnamomi in B. attenuata and B. menziesii, (68%, p = 0.00002 and 60%, p = 0.00002, respectively), followed by BBA [52%, P = 0.00004, and 45%, p = 0.00003). Injection was effective in B. menziesii (42% reduction, p = 0.00006), but the reduction in colonisation in injected B. attenuata was not significantly different from untreated controls. In Jarrah, stem colonisation was reduced by 33% in injected trees (p = 0.003), but BBA was ineffective. Application time for BBA was 26-43% of that for other treatments. However, the cost of the carrier (modified heptamethyltrisiloxane) made BBA treatment 1.5-1.8 times more expensive per unit of basal area than the other methods.

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.

Fifteen native Western Australian legumes were assessed for their potential to biologically control Phytophthora cinnamomi. Biological control was assessed in a controlled situation, conducive to P. cinnamomi, and was based on susceptibility to the pathogen, ability to reduce soil inoculum, amount of asymptomatic root infection and ability for P. cinnamomi to effectively sporulate from asymptomatically infected roots. Acacia extensa, Acacia stenoptera and Acacia alata along with Acacia pulchella, were identified as species with the highest potential for biological control of P. cinnamomi. Acacia urophylla and Viminaria juncea exhibited the least potential for biological control; these are more likely to harbour the pathogen and provide a source of inoculum when conditions become conducive for P. cinnamomi growth and development. These findings have important implications for managing the rehabilitation of bauxite-mined P. cinnamomi-infested areas and severely disease-affected forest. By manipulating rehabilitation seed mix ratios, the density of legume species that suppress P. cinnamomi inoculum in the soil can be increased and the density of those that harbour the pathogen can be reduced. This could potentially contain the activity of P. cinnamomi soil inoculum in infested areas to protect susceptible species and enhance species diversity. Further research is required to ascertain the action of suppression before implementing control measures.

Five Acacia species native to Western Australia were assessed for their potential to protect the highly susceptible species Banksia grandis Wield from infection by the plant pathogen Phytophthora cinnamomi Rands. In a rehabilitated bauxite pit at Jarrahdale 55 km south-east of Perth and in a glasshouse trial, B. grandis planted either alone or with A. pulchella R.Br., A. urophylla Benth., A. extensa Lindl., A. lateriticola Maslin or A. drummondii Lindl., was soil inoculated with P. cinnamomi. It could only be shown that A. pulchella significantly protected B. grandis from P. cinnamomi infection in the rehabilitated bauxite pit trial up to 1 year after inoculation. This confirms the potential of this species for biological control of the pathogen in infested plant communities. The observed protection was not the result of a decrease in soil temperature or moisture. Protection was not emulated in a glasshouse trial where optimum environmental conditions favoured P. cinnamomi. Despite a delay in infection of B. grandis planted with Acacia spp., none of the five species definitively protected B. grandis from P. cinnamomi. However, in the glasshouse trial, A. pulchella, A. extensa, A. lateriticola and A. drummondii did significantly reduce the soil inoculum of P. cinnamomi, indicating a possible biological control effect on the pathogen. The mechanisms of biological control are discussed and the implications for management of rehabilitated bauxite mined areas and forests severely affected by P. cinnamomi are considered.

The introduced soilborne plant pathogen Phytophthora cinnamomi has caused significant habitat loss and fragmentation throughout Western Australia's jarrah forest (Eucalyptus marginata). However, no detailed study has examined how this could impact on the abundance of small mammals. In this study the abundance of the yellow-footed or mardo (Antehcinus flavipes leucaogaster) (Marsupialia:Dasyuridea) was assessed and compared between P. cinnamomi infested areas to healthy forest areas using a mark, release-recapture technique. A total of six trap sites were established, 4 diseased sites and 2 healthy forest sites. A total of 386 captures were recorded from 80 individuals over 4070 trap nights for a total trap success of 6.9%. A significant (p=0.001) difference in captures was recorded across all sites. A total of 77 number of captures from 23 individuals were recorded at the four dieback sites, while 309 number of captures were recorded from 57 individuals at the two healthy sites. In conclusion, the loss of vegetation structure and floristic diversity caused by this pathogen impacted on mardo significantly and likely to have had a similar impact on other small mammals in the jarrah forest.

Phosphite is increasingly being used to control for dieback caused by Phytophthora cinnamomi. We wished to study the likelihood of P cinnamomi evolving resistance to phosphite, given the clonal populations of the fungus present in Western Australia. Isolates of P cinnamomi were collected from areas where phosphite has been used intensively for up to 15 years (avocado orchards) as well as areas of less frequent and no use of phosphite. Our testing involved stem inoculating a clonally propagated host (Leucadendmn sp.) that was treated with one of three levels of phosphite (0%, 0.25% and 0.5%). The extent of colonisation by each P. cinnamomi isolate was detem1ined after 8 days of incubation in a controlled temperature plant growth cabinet. Initial trials showed that less aggressive isolates are not present in populations obtained from areas where phosphite has been used. Also, the few isolates that colonise the phosphite treated host to a large extent all come from phosphite treated areas. However, the interaction of aggressiveness of isolates with the length of their previous exposure to phosphite was not consistent. These results may reflect the repeated sampling of the same, more aggressive isolate from a single avocado orchard rather than the development of aggressiveness in response to phosphite treatment. A replicated trial produced similar though less significant results, but required much longer incubation for disease .to develop, probably due to the slightly more mah1re clonal plant material used.

Phytophthora cinnamomi is a major oomycete pathogen of an extensive range of mainly woody plants. We conducted genetic mapping of P cinnamomi to localise genes involved in pathogenicity. Presented here are the genetic maps of five P. cinnamomi isolates developed from our analysis of four outbred mapping populations. The mapping populations were constructed using a common Al parent and four different A2 parents. Because analysis has been restricted to mapping populations of F1 hybrid progeny in this diploid species, we chose to use microsatellite fragment length polymorphisms (MLFP) as genetic markers. This technique combines the high polymorphism and codominance of microsatellites with the AFLP technique and needs no prior sequence information. The analysis yielded between one and four informative loci per primer combination (equivalent to one AFLP gel run). These genetic maps will be applied to QTL mapping of pathogenicity characters in the P. cinnamomi genome.

Sporulation by Phytophthora cinnamomi is significantly suppressed in forest sites dominated by Acacia pulchella compared to forest sites dominated by species of Proteaceae. In this investigation an inoculation trial was conducted to determine the effect of 14 other Western Australian native legumes on population levels of P. cinnamomi in the soil compared to Banksia grandis. Direct plating of soil onto Phytophthora selective agar was used to quantify inoculum levels. A. alata, A. extensa A. latericola, A. pulchella, A. stenoptera, Kennedia coccinea and K. prostrata showed low mortality and decreased inoculum of P. cinnamomi in soil compared to B. grandis. A. drummondii, A. urophylla and Viminaria juncea also showed low mortality bu, had no effect on inoculum of P. cinnamomi. Bossiaea aquijolium, Daviesia decurrens, Hovea chorizemifolia, Labichea punctata, Mirbelia dilatata and B. grandis showed high mortality due to P. cinnamomi infection. Of these species population levels were only quantified from B. grandis pots for comparison.

Summer rainfall seldom occurs in the south-west of Western Australia. Flora of the region has evolved under a Mediterranean climate having hot dry summers with rare thunder storms, and cool wet winters. The consequence of high summer rainfall is significant because the resulting conditions can favour an outbreak of the introduced soil pathogen, Phytophthora cinnamomi, to which many plant species in the south-west forests are susceptible. A glasshouse experiment compared the response of drought stressed and non-stressed Eucalyptus marginata (jarrah) plants when inoculated with P. cinnamomi after a simulated summer rainfall event. Clonal plants, resistant or susceptible to P. cinnamomi, were tested. The moisture content of the container substrate for inoculated and non-inoculated plants was either kept at container capacity or at a pre-determined level just above that of the wilting point of each plant for 3 weeks. Sudden restoration to container capacity simulated summer rainfall and plants were inoculated immediately. Higher proportions of non-stressed clonal plants, both resistant and susceptible, became infected and were more extensively colonized by the pathogen than plants subjected to drought Results supported our hypothesis : tissue of drought affected E. marginata plants is less susceptible to infection by P. cinnamomi than tissue of plants which have recently experienced no water deficit.

Mortality of Eucalyptus marginata seedlings following infection by Phytophthora cinnamomi was lower when planted with Acacia pulchella than when planted with Banksia grandis. The protective effects of native legumes other than A. pulchella against P. cinnamomi have not been determined. Field and glasshouse inoculation trials were set up to investigate the protective potential of five Western Australian native Acacia species for B. grandis. In the field only A. pulchella protected B. grandis against P. cinnamomi infection. Mortality of B. grandis planted with A. pulchella was as low as uninoculated B. grandis planted alone. Mortality of B. grandis planted with A. urophylla, A. extensa, A. latericola or A. drummondii was high and similar to inoculated B. grandis planted alone. In the glasshouse none of the Acacia species definitively protected B. grandis. Mean mortality due to infection by P. cinnamomi of B. grandis planted with A. pulchella or A. latericola was less than the control. However the remaining B. grandis seedlings died following infection by an unidentified fungus, hence protection could not be concluded.

Soil moisture and the type of organic matter colonised by Phylophlhora cinnamomi significantly affected long-term survival of the pathogen. Banksia grandis stem pieces, and root tips of Eucalyptus marginata (jarrah) colonised with P. cinnamomi were placed into pots filled with soil from the jarrah forest or an adjacent rehabilitated bauxite mine site in the south west of Western Australia. The soil was either maintained at container capacity, or allowed to dry-out slowly from container capacity. Samples were harvested over a 210-day period and assessed for P. cinnamomi survival. P. cinnamomi was recovered after 210 days from banksia stems (98% colonisation) and eucalypt root tips (45% colonisation) from both soil types when the soil was maintained at container capacity. However when the soils were allowed to dry, the pathogen was not recovered after 112 days from either banksia stems or eucalypt roots. Soil origin did not influence P. cinnamomi survival for either inoculum type. These findings indicate that under moist conditions the pathogen can survive in small pieces of organic matter for extended periods of time.

Seed-grown trees and six clonal lines of 3-5-4-5-year-old Eucalyptus marginata (jarrah) growing in a rehabilitated bauxite mine site in the jarrah forest were underbark-inoculated on lateral branches (1995) or simultaneously on lateral branches and lateral roots (1996) with isolates of Phytophthora cinnamomi in late autumn. Individual seedlings from which the clonal lines were derived had previously been assessed as either resistant (RR) or susceptible (SS) to P. cinnamomi. At harvest, the acropetal lesion and colonization lengths were measured. Overall, the length of colonization in roots and branches was more consistent as a measure of resistance than lesion length, because colonization length recorded the recovery of P. cinnamomi from macroscopically symptomless tissue ahead of the lesion which, on some occasions, was up to 6 cm. In both trials, one RR clonal line was able to contain the P. cinnamomi isolates consistently, as determined by small lesion and colonization lengths in branches and roots. In contrast, the remaining two RR clonal lines used in both trials were no different from the SS line in their ability to contain lesions or colonization. These latter two RR lines may therefore not be suitable for use in rehabilitation of P. cinnamomi-infested areas. Differences in lesion and colonization lengths among P. cinnamomi isolates occurred only in the 1995 trial. Colonization and lesion lengths in branches were up to eight times greater in 1996 than in 1995, but the relative rankings of clonal lines were consistent between trials. Although colonization was always greater in branches than roots, the relative rankings of the lines were similar between branch and root inoculations. Branch inoculations are a valid option for testing the resistance and susceptibility of young jarrah trees to P. cinnamomi.

A simple, effective method of inoculating Eucalyptus marginata (jarrah) stems with the pathogen Phytophthora cinnamomi was developed. There were four criteria to be addressed when developing this technique. A method was required that did not necessitate the wounding of plant tissue, that simulated surface water ponding (often seen in riplines on rehabilitated mine sites), that was applicable to both glasshouse trials and field trials, and that was less labour intensive than previously published methods. In the development of this new method in the glasshouse, agar plugs, colonised by P. cinnamomi, were placed face-down onto unwounded green stem and periderm of 18-month-old jarrah seedlings. The highest percentage of stems infected was obtained when stems were pre-moistened before the inoculum plug was held in place with wet cotton wool and Parafilm. This technique is simple to use under field conditions.

Survival of 1-year-old plants of three clonal lines of Eucalyptus marginata (jarrah), two ranked as resistant (RR1 and RR2) and one as susceptible (SS1) to Phytophthora cinnamomi, was assessed after pathogen inoculation with either mycelial mats underbark or zoospores on the stem. Plants were grown at 15, 20, 25 and 30°C. Method of inoculation did not produce comparable mortalities of the clonal lines, particularly at 25 and 30°C. At these temperatures, all three clonal lines had 100% mortality when inoculated underbark, but when inoculated with zoospores, RR1 had 60% survival and lines SS1 and RR2 had 100% mortality. Generally, the level of resistance of all clonal lines declined with increasing temperature. RR2 had consistently higher mortality than SS1, and is therefore not considered resistant. Lesion development was also measured in detached stems of RR1 and a susceptible clonal line (SS2) each inoculated underbark with four different P. cinnamomi isolates. Stems were assessed for lesion development at 20, 25 and 30°C for 4 days. For all four isolates, detached stems of RR1 generally had smaller lesions than those of SS2, particularly at 30°C. The increase in lesion length with increasing temperature was greatest for SS2. Detached stems may have potential in screening for jarrah resistant toP. cinnamomi and allow identification of susceptible clonal lines at 30°C.

Botanists have likened the impact of Phytophthora cinnamomi in Australian plant communities to that of the last ice age, which affected a large number of plant families, genera and species within these families. Phytophthora cinnamomi affects the floristics and structure of many unique plant communities. We discuss the impact of this pathogen and our current knowledge of its biology, genetics and pathology in Western Australian plant communities and the current management strategies used to limit its spread and impact. We hope that the knowledge obtained from some of our experiences in managing this pathogen in Western Australian natural ecosystems will be of some benefit to researchers studying Phytophthora diseases in Quercus, Alnus and Castanea in Europe and America.

The ability of phosphite to control Phytophthora cinnamomi Rands in five Western Australian native plant species was examined. Foliar application of phosphite slowed, but did not completely inhibit, colonisation of stems by P. cinnamomi. For example, in Banksia hookeriana Meisn. inoculated 2 weeks after phosphite application, 5 g phosphite/L inhibited the growth rate of P. cinnamomi by 57% compared with the non-phosphite-treated plants. The longevity of phosphite efficacy varied with plant species. Foliar application of 5 and 10 g phosphite/L decreased the growth rate of P. cinnamomi in Diyandra sessilis (Knight) Domin, for at least 12 months after it was applied. Application rates of 5 and 10 g phosphite/L for Banksia grandis Willd. and 10 g/L for B. hookeriana were effective for at least 18 months after application. In Hibbertia commutata Steud. and Dampiera linearis R.Br., phosphite was effective for less than 6 and 12 months, respectively. In a second trial, plants were inoculated with P. cinnamomi at different time periods after phosphite was applied and time to death was recorded. There was a range of responses depending on the plant species and time of year they were inoculated. The initial levels of phosphite in roots and stems of A grandis, B. hookeriana and D. sessilis and the rate of decrease of phosphite in these tissues differed between plant species. In general, concentrations of phosphite in stems were higher or equivalent to those in roots. This study indicates that the long-term efficacy of phosphite depends on both the plant species treated and the time of year the plants are infected with P. cinnamomi.

This study examined the ability of foliar applications of the fungicide phosphite to contain colonisation of Phytophthora cinnamomi in a range of plant species growing in natural plant communities in the northern sandplain and jarrah (Eucalyptus marginata) forest of south-western Australia. Wound inoculation of plant stems with P. cinnamomi was used to determine the efficacy of phosphite over time after application. Colonisation by P. cinnamomi was reduced for 5–24 months after phosphite was applied, depending on the concentration of phosphite used, plant species treated and the time of phosphite application. Plant species within and between plant communities varied considerably in their ability to take up and retain phosphite in inoculated stems and in the in planta concentrations of phosphite required to contain P. cinnamomi. As spray application rates of phosphite increased from 5 to 20 g L–1, stem tissue concentrations increased, as did the ability of a plant species to contain P. cinnamomi. However, at application rates of phosphite above 5 g L–1 phytotoxicity symptoms were obvious in most species, with some plants being killed. So, despite 10 and 20 g L–1 of phosphite being more effective and persistent in controlling P. cinnamomi, these rates are not recommended for application to the plant species studied. The results of this study indicate that foliar application of phosphite has considerable potential in reducing the impact of P. cinnamomi in native plant communities in the short-term. However, in order to maintain adequate control, phosphite should be sprayed every 6–12 months, depending on the species and/or plant community.

The efficacy of phosphite to control the production of zoospores of Phytophthora cinnamomi on infected trees grown in a glasshouse and in a revegetated mined area was examined. Banksia grandis and Eucalyptus marginata seedlings in the glasshouse and E. marginata seedlings in the minepit were sprayed with 0, 5 and 10 g phosphite L−1. In both trials, zoospores were produced from infected tissue of plants treated with all concentrations of phosphite. In the glasshouse, spray application of 5 and 10 g phosphite L−1 significantly reduced the production of zoospores from both B. grandis and E. marginata seedlings. In the mined area there was a similar, though nonsignificant, reduction in the number of zoospores produced from phosphite-treated and nontreated E. marginata seedlings. However, the average number of zoospores produced was greater in plants not treated with phosphite (1·75 zoospores mL−1) than from plants treated with 5 or 10 g phosphite L−1 (0·04 and 0·09 zoospores mL−1, respectively). Pimelea ferruginea leaves were used to bait the water surrounding the plants in the mined area to determine if zoospores produced from phosphite-treated plants were able to infect plant material. Significantly more baits were infected by zoospores from plants not treated with phosphite compared with plants treated with 5 or 10 g phosphite L−1. These results suggest that phosphite reduces, but does not prevent, the production of viable zoospores on infected trees. Thus phosphite application may not remove the risk of P. cinnamomi spreading from infested, sprayed areas.

Although phosphite has been effective in the control of P. cinnamomi in E. marginata (jarrah), the biochemical mechanisms behind phosphite protection are poorly understood. Using an aeroponics system, jarrah clones with moderate resistance to P. cinnamomi were treated with foliar applications of phosphite (0 and 5 g L−1). The roots were inoculated with zoospores of P. cinnamomi at 4 days before and 0, 2, 5, 8 and 14 days after phosphite treatment. Root segments were then analysed for activity of selected host defence enzymes (4-coumarate coenzyme A ligase [4-CL], cinnamyl alcohol dehydrogenase [CAD]) and the concentration of soluble phenolics and phosphite. Lesion development was most effectively reduced when phosphite concentrations within the roots were highest (i.e. days 8–14). During this time, the levels of host defence enzymes remained relatively unchanged. Lesion development was also effectively restricted when phosphite concentrations within the roots were lowest (i.e. days 2 and 5); a significant increase in host defence enzymes was associated with this decrease in lesion development. It was concluded from these studies that the effect of phosphite in controlling the pathogen is determined by the phosphite concentration at the host–pathogen interface. When phosphite concentrations within the roots are low, phosphite interacts with the pathogen at the site of ingress to stimulate host defence enzymes. At high phosphite concentrations, phosphite acts directly on the pathogen to inhibit its growth before it is able to establish an association with the host, and the host defences remain unchanged.

Western Australia is renowned as a region of exceptional plant species richness—more than 7,000 species of native vascular plants occur in the state (19), and of these, over 3,000 are endemic (30). The native plant communities in the southwestern part of the state are also the setting for what has been described as “a biological disaster of global significance for conservation of areas of great biodiversity and a major problem for wood based and extractive industries” (42). The cause of this “disaster” is Phytophthora root and collar rot (PRCR) disease, with Phytophthora cinnamomi being the predominant pathogen. This pathogen directly affects over 2,000 of the 7,000 native species (59), and its indirect effects are still to be elucidated.

Pre-treatment of plants with foliar sprays of 0.2, 0.5 and 2% phosphite restricted colonisation by Phytophthora cinnamomi in inoculated stems of Adenanthos barbiger and Daviesia decurrens, and led to a reduction in the isolation of P. cinnamomi from these stems in comparison with unsprayed plants. In plants treated with 2% phosphite,P. cinnamomi was not isolated from D. decurrens but was isolated from 22% of the stems of A. barbiger. InXanthorrhoea preissii, colonisation by, and isolation of,P. cinnamomi from inoculated roots was not significantly affected by pre-treatment of the foliage with 0.2, 0.5 and 2% phosphite. Very low concentrations of phosphite were detected in the roots of X. preissii (maximum mean of 2.2 g/g dry weight), in comparison with the phosphite concentrations measured in the foliage of A. barbiger and D. decurrens plants treated with phosphite (maximum means of 80 and 871 g/g dry weight, respectively). Treatment with 0.2% phosphite resulted in minimal phytotoxicity in each of the three species, whereas treatment with 2% phosphite led to the development of severe phytotoxicity symptoms. This study indicates that phosphite has potential for the management of P. cinnamomi in native plant communities.

This project aimed to assess whether foliar application of phosphite is a practicable, economic and effective way of controlling Phytophthora cinnamomi in native plant communities.

Surface ponding of water is evident in many recently (0—3 years old) rehabilitated minepits; this occurs at the bottom of the pit but also in riplines on the upper slopes of the pit: The presence of surface and subs urface ponds has the potential to affect plant growth and survival. The aims of this project were to monitor the duration and frequency of ponding, and to monitor oxygen levels to assess the potential for waterlogging to occur. Observations at the Huntly mine found that ponding is highly variable within and between rehabilitated minepits. Level floats attached to data loggers in six rehabilitated minepits were used to determine the duration and frequency of surface ponding. Between September and May 1997 depressions held water between 5 and 25% of the time. The average duration of ponding each week was highly correlated to the weekly rainfall. We believe that surface ponding can be caused by three circumstances: (i) clay collecting in depressions, (ii) low infiltration capacity of a sub-surface clay layer or (iii) a surface expression of subsurface accumulation of water. Seven minepits with obvious areas of ponding were selected for monitoring of the depth of sub-surface ponding and oxygen content of the water. Piezometers were placed in 78 ponds at depths of 30, 60 and up to 90 cm. There were five types of surface ponds and profiles identified; (a) fast draining ponds with little impediment to water movement through the soil, (b) slowly draining ponds with some impediment to water movement through the soil, (c) ponds that drained into a sub-surface pond that prevented water movement, (d) ponds that were actually drainage sumps formed in low lying areas of the pits and (e) ponds overlying a sub-surface water channel. About 30% of the ponds were of type (c) and (d), and were associated with subsurface water that had a low oxygen concentration. Thus, the potential exists in early vegetation rehabilitation for surface ponding to be associated with sub-surfa

Plants of a Eucalyptus marginata clone (1JN30) were grown in aeroponics chambers that could be sealed to allow the manipulation of oxygen levels in the root environment. Roots were grown for varying periods of hypoxia (0, 2, 5, 11 or 29 days) before being inoculated with zoospores of Phytophthora cinnamomi. A similar set of roots was inoculated 3 days after the hypoxia treatments. Root extension was reduced at the end of all the hypoxia treatments. Six days after the hypoxia treatments, root extension had returned to normal for roots that had been exposed to 5 days of hypoxia, while for roots exposed to 11 or 29 days, extension was half the normal rate. Longitudinal sections of root tips after 5, 11 or 29 days of hypoxia indicated that the treatment caused a reduction in cell division, but not in cell expansion. In the case of roots exposed to 2 days of hypoxia, the apical meristem appeared normal at the end of the treatment, but 3 days after the return to normal oxygen conditions many of the apical meristems had died and the roots had a clubbed appearance. Thus, E. marginata roots have an acclimatization period to hypoxia of between 2 and 5 days, after which they can tolerate hypoxia for extended periods. However, their ability to recover rapidly posthypoxia is reduced after 11 days' exposure. The percentage of inoculated roots that became infected and developed lesions was significantly reduced in roots inoculated immediately posthypoxia, compared with roots grown under normal oxygen conditions. As root growth recovered, lesion development also returned to normal. Thus, the rate of lesion development was related to the rate of root extension at the time of inoculation.

Eucalyptus marginata growing on rehabilitated bauxite mines may be exposed to waterlogging (hypoxia) at the roots, as well as ponding around the stems at the soil surface. This paper examines whether these conditions may predispose stems of E. marginata to infection by Phytophthora cinnamomi. Plants of E. marginata clones resistant and susceptible to P. cinnamomi were grown in an aeroponics system that could be sealed to allow the manipulation of oxygen levels in the root zone to simulate waterlogging. Plants grown under normal oxygen conditions were compared with those whose root zone was exposed to hypoxia (2mgO2L-1) before, during or after the sterns were inoculated with zoospores of E cinnamomi. Inoculation was achieved by constructing receptacles around the stems that could hold water and zoospores. Stomatal conductance increased in plants whose roots had been exposed to hypoxia. This effect lasted for at least 2 weeks after the resumption of normal oxygen conditions. P. cinnamomi entered and colonized ponded stems; however, there were no visible lesions on stems 14 days after inoculation. For any given clone of E. marginata, the extent of colonization was significantly greater in stems whose root zone had been exposed to hypoxia than in control stems. The activity of the plant defence-associated enzymes PAL, 4-CL and CAD and the concentrations of soluble phenolics were higher in the stems of plants whose roots were exposed to hypoxia, but the increase in activity in response to colonization was much greater for plants whose roots were under normal aerobic conditions. The greatest difference between colonized and noninoculated plants was observed at the colonization front. Peroxidase activity increased after tissues were colonized, rather than preceding the colonization as seen with the other enzymes. The stress induced by root hypoxia remained after roots were returned to normal oxygen conditions. Plants with root hypoxia showed greater s

Bauxite mining in Western Australia occurs in forest infested with Phytophthora cinnamomi. The mining company Alcoa identified the need for a treatment to eradicate P. cinnamomi from relatively small volumes (<60 m 3) of topsoil and gravel. This study examined the efficacy of copper sulphate (CuSO4 ) in eradicating P. cinnamomi within 2 h and after 5 days. Both agar and in vitrosoil tests were used. Concentrations up to 137.5 mg/L Cu 2+ in potato-dextrose agar did not kill or totally inhibit growth of the pathogen. Vermiculite infested with P. cinnamomi was added to topsoil and gravel treated with concentrations up to 5 g CuSO4 /kg soil. Direct plating of vermiculite and baiting of soils with leaves of Pimelea ferruginea and cotyledons of Eucalyptus sieberi were used to determine the disease-suppressing ability of CuSO4 . Applications of up to 5 g CuSO4 /kg soil were insufficient to kill P. cinnamomi after 2 h exposure in both soil types. However, infection of baits in gravel did not occur after 5 days exposure. The results indicate that CuSO4 application would not be appropriate where rapid and total eradication of P. cinnamomi is required but it may be valuable where the aim is to significantly reduce the risk of spreading the pathogen.