Kordyana brasiliensis is a pathogenic biotrophic fungus native to Brazil. It was deliberately released in New Zealand and Australia for the biological control of the invasive environmental weed Tradescantia fluminensis. The fungus produces two different spore types, basidiospores and asexual conidia, but the infection ability of conidia and the microclimatic variables that influence basidiospore germination processes are unknown. Results of controlled environment trials showed that conidia produced on either solid or liquid media were able to cause leaf lesions on T. fluminensis plants, but not when applied at the lowest suspension density tested (1 × 104 conidia/ml) or when conidia were harvested from young (<7 days) cultures. The successful infection of T. fluminensis plants inoculated with conidia (derived from a single basidiospore culture) and subsequent development of sexual structures in lesions indicate that K. brasiliensis is homothallic. The mechanism of infection, however, remains unclear because penetration of the host by thin hyphae produced by conidia on leaf surfaces was not observed in the samples examined by light microscopy. The influence of temperature and wetness period on basidiospore germination processes in vitro was investigated in a second set of experiments. Basidiospore germination and germ-tube elongation were significantly influenced by the interaction of both temperature and wetness period duration (optimal germination at 15-25 °C and germ-tube elongation at 20-22.5 °C). Extended wetness periods buffered the effects of suboptimal temperatures on basidiospore germination until the maximum threshold temperature of 30 °C was reached. Conidia formed on sterigmata-like outgrowths on basidiospore germ-tubes after exposure to extended wetness periods (>18 h) and a relatively broad temperature range (15-25 °C). The potential role of conidia in the life cycle of the fungus is discussed. This is the first study of a Kordyana species to demonstrate the ability of conidia to cause infection on its host and investigate the influence of microclimate variables on basidiospore germination processes. Results of this study can be used as a basis for future research to examine the life cycle, mating system genetic basis and epidemiology of K. brasiliensis.

Impacts of weed biocontrol agents can be spatially and temporally dynamic. Identifying the specific drivers and contexts of variable outcomes in weed biocontrol programs can inform release approaches and integrated weed management plans. Kordyana brasiliensis is a foliar pathogen which is host-specific to the invasive environmental weed Tradescantia fluminensis. Kordyana brasiliensis has been released in New Zealand and Australia as a biocontrol agent of T. fluminensis. Reports of K. brasiliensis impacts on T. fluminensis populations has been limited to observational reports and quantitative studies undertaken in a small number of areas. Additional research was required to evaluate broadscale establishment and impacts of K. brasiliensis on T. fluminensis across broad geographical and temporal scales. A field study was established in eastern Australia releasing K. brasiliensis at 14 sites with dense T. fluminensis infestations across an 800 km latitudinal gradient. Despite rapid broadscale establishment (by 6-months), K. brasiliensis disease levels varied significantly over temporal and spatial gradients and was strongly associated with macroclimate variability. Lower disease incidences were observed with higher maximum temperatures, whereas high disease severity was strongly associated with more rain days. The impacts of K. brasiliensis on T. fluminensis populations varied across climate contexts, with greater declines in weed abundances occurring in warmer areas with more frequent rainfall events. Host weed abundances remained stable in drier areas. Models identifying drivers of agent impacts can be incorporated into weed management planning to identify and prioritise areas for alternative management methods where there is limited likelihood of biocontrol success.

Impacts of weed biocontrol agents can be spatially and temporally dynamic. Identifying the specific drivers and contexts of variable outcomes in weed biocontrol programs can inform release approaches and integrated weed management plans. Kordyana brasiliensis is a foliar pathogen which is host-specific to the invasive environmental weed Tradescantia fluminensis. Kordyana brasiliensis has been released in New Zealand and Australia as a biocontrol agent of T. fluminensis. Reports of K. brasiliensis impacts on T. fluminensis populations has been limited to observational reports and quantitative studies undertaken in a small number of areas. Additional research was required to evaluate broadscale establishment and impacts of K. brasiliensis on T. fluminensis across broad geographical and temporal scales. A field study was established in eastern Australia releasing K. brasiliensis at 14 sites with dense T. fluminensis infestations across an 800 km latitudinal gradient. Despite rapid broadscale establishment (by 6-months), K. brasiliensis disease levels varied significantly over temporal and spatial gradients and was strongly associated with macroclimate variability. Lower disease incidences were observed with higher maximum temperatures, whereas high disease severity was strongly associated with more rain days. The impacts of K. brasiliensis on T. fluminensis populations varied across climate contexts, with greater declines in weed abundances occurring in warmer areas with more frequent rainfall events. Host weed abundances remained stable in drier areas. Models identifying drivers of agent impacts can be incorporated into weed management planning to identify and prioritise areas for alternative management methods where there is limited likelihood of biocontrol success.

We investigated global patterns of population genetic diversity and structure for the clonal invasive scrambler, Cape ivy (Delairea odorata Lem., family Asteraceae), to help optimise exploratory surveys of candidate biocontrol agents in its native range, South Africa. We collected more than 1000 Cape ivy samples from 122 populations throughout South Africa and its introduced ranges (Australia, New Zealand, mainland USA, Hawai'i and southern France), and performed population genetic diversity and structure analyses based on single nucleotypic polymorphisms (SNPs). On average, population genetic diversity values were six times higher in South Africa than all introduced populations, although these values were three times higher for the mainland USA populations than those in Australia, Hawai'i and New Zealand. Populations were strongly differentiated with limited gene flow between the native and introduced ranges (intercontinental scale) and between sites within each range (regional scale). All Australian, New Zealand, Hawai'ian and some Californian populations had Fst values approaching zero, likely arising from a single clonal accession derived from the same ancestral population, likely from the Western Cape Province of South Africa. The remaining mainland USA populations showed signs of multiple introductions and admixture patterns. Our results show that human-assisted dispersal of Cape ivy through the ornamental plant trade can overcome genetic (bottleneck) barriers to global invasion, especially for clonal accessions of the plant. We recommend that host-specificity testing of candidate biocontrol agents for Cape ivy in the Australian and New Zealand contexts should source agents from the Western Cape Province of South Africa.

Analysis of environmental DNA (eDNA) enables indirect detection of species without the need to directly observe and sample them. For biosecurity and invasion biology, eDNA-based methods are useful to address biological invasions at all phases, from detecting arrivals to confirming eradication of past invasions. We conducted a systematic review of the literature and found that in biosecurity and invasion biology, eDNA has primarily been used to detect new incursions and monitor spread in marine and freshwater ecosystems, with much slower uptake in terrestrial ecosystems, reflecting a broader trend common to the usage of eDNA tools. In terrestrial ecosystems, eDNA research has mostly focussed on the use of eDNA metabarcoding to characterise biodiversity, rather than targeting biosecurity threats or non-native populations. We discuss how eDNA-based methods are being applied to terrestrial ecosystems for biosecurity and managing non-native populations at each phase of the invasion continuum: transport, introduction, establishment, and spread; across different management options: containment, control, and eradication; and for detecting the impact of non-native organisms. Finally, we address some of the current technical issues and caveats of eDNA-based methods, particularly for terrestrial ecosystems, and how these might be solved. As eDNA-based methods improve, they will play an increasingly important role in the early detection and adaptive management of biological invasions, and the implementation of effective biosecurity controls.

The identity and diversity of Kordyana species on three native species of Commelinaceae in Australia were studied following surveys in 2020–2022 for Kordyana brasiliensis, which had been deliberately released as a biocontrol agent for the environmental weed Tradescantia fluminensis. Three new species of Kordyana are described from Australia based on DNA sequence analysis of the ITS and LSU rDNA regions, morphology, host associations, and geographic distributions. Two new species, Kordyana spectabilis on Aneilema acuminatum and Kordyana luteoalba on Pollia crispata, occur in shaded rainforest habitats in eastern Australia. The third new species, Kordyana occidentalis on Commelina ensifolia, occurs in forests and woodlands of the Kimberley region of Western Australia. Morphological descriptions are provided for these three new species of Kordyana as well as for the conidial stage of K. brasiliensis.

A concern in weed biological control research is the potential for candidate biocontrol agents to impact not only the target weed but also native or economically important flora. The degree of evolutionary relatedness between the target weed species and a non-target species is a key predictor of the susceptibility of the non-target to the biocontrol agent. To manage this risk, biocontrol practitioners need to understand the phylogenetic position of the host weed relative to non-target plant species. However, comprehensively sampled phylogenetic trees are often unavailable, with incomplete information scattered across multiple publications. Further, older published phylogenies based on Sanger sequence data often lack branch resolution and support, which increases uncertainty in biocontrol decision making. Decreasing sequencing cost and technological advances have led to phylogenomic approaches being more widely used to understand evolutionary relationships between species. For example, target capture sequencing methods using bait kits such as Angiosperms353 enable cost-effective and timely phylogenomic-level analysis of flowering plant groups at different scales. Here, we introduce a workflow to embed a comprehensive understanding of evolutionary relationships into the efficient development of host test lists in weed biological control. We demonstrate the effectiveness of the workflow through a case study on the major crop weed flaxleaf fleabane (Erigeron bonariensis). Phylogenomic analysis was conducted on 280 species of the tribe Astereae (family Asteraceae) occurring in Australia and New Zealand, clarifying relationships between the target species and related clades of native and non-native Astereae. We consider the phylogenetic tree in the context of a previously proposed host test list and discuss taxonomic implications, highlighting avenues of future molecular-based work to uncover the origin of Australian fleabanes. This study provides a workflow and demonstrates the practical application of target sequence capture for phylogenomic inference to support risk analysis and decision making in classical weed biological control.

In 2008, a fungal pathogen causing severe necrotic leaf and stem lesions on Euphorbia paralias (commonly referred to as sea spurge) was collected in France. The fungus has recently been described as Venturia paralias and offers potential for the classical biological control of sea spurge in Australia, where the plant is invasive in dune and foredune ecosystems. To explore the host range of V. paralias, a series of experiments comprising 45 species from the Euphorbiaceae, Picrodendraceae and Phyllanthaceae families were performed. In addition, the development of V. paralias on leaves of sea spurge and the other species inoculated was examined microscopically. Results revealed that V. paralias is highly specific, only causing disease symptoms on sea spurge and Euphorbia segetalis, its most phylogenetically related species tested that is present in Australia. Microscopic observations showed that the infection process of V. paralias on its two susceptible hosts is similar to that of other Venturia species, with characteristic expanded hyphal networks within the subcuticular space of leaves. In contrast, V. paralias did not penetrate leaves of other species inoculated, except for three (Euphorbia myrsinites, Euphorbia helioscopia and Mercurialis annua) on which it penetrated the leaf cuticle and developed an initial infection hypha that did not expand any further. Results from this study support the conjecture that V. paralias will not pose a threat to valued non-target Euphorbiaceae species should the fungus be approved for introduction to Australia for the biological control of sea spurge.

Novel species of fungi described in this study include those from various countries as follows: Antarctica, Cladosporium arenosum from marine sediment sand. Argentina, Kosmimatamyces alatophylus (incl. Kosmimatamyces gen. nov.) from soil. Australia, Aspergillus banksianus, Aspergillus kumbius, Aspergillus luteorubrus, Aspergillus malvicolor and Aspergillus nanangensis from soil, Erysiphe medicaginis from leaves of Medicago polymorpha, Hymenotorrendiella communis on leaf litter of Eucalyptus bicostata, Lactifluus albopicri and Lactifluus austropiperatus on soil, Macalpinomyces collinsiae on Eriachne benthamii, Marasmius vagus on soil, Microdochium dawsoniorum from leaves of Sporobolus natalensis, Neopestalotiopsis nebuloides from leaves of Sporobolus elongatus, Pestalotiopsis etonensis from leaves of Sporobolus jacquemontii, Phytophthora personensis from soil associated with dying Grevillea mccutcheonii. Brazil, Aspergillus oxumiae from soil, Calvatia baixaverdensis on soil, Geastrum calycicoriaceum on leaf litter, Greeneria kielmeyerae on leaf spots of Kielmeyera coriacea. Chile, Phytophthora aysenensis on collar rot and stem of Aristotelia chilensis. Croatia, Mollisia gibbospora on fallen branch of Fagus sylvatica. Czech Republic, Neosetophoma hnaniceana from Buxus sempervirens. Ecuador, Exophiala frigidotolerans from soil. Estonia, Elaphomyces bucholtzii in soil. France, Venturia paralias from leaves of Euphorbia paralias. India, Cortinarius balteatoindicus and Cortinarius ulkhagarhiensis on leaf litter. Indonesia, Hymenotorrendiella indonesiana on Eucalyptus urophylla leaf litter. Italy, Penicillium taurinense from indoor chestnut mill. Malaysia, Hemileucoglossum kelabitense on soil, Satchmopsis pini on dead needles of Pinus tecunumanii. Poland, Lecanicillium praecognitum on insects' frass. Portugal, Neodevriesia aestuarina from saline water. Republic of Korea, Gongronella namwonensis from freshwater. Russia, Candida pellucida from Exomias pellucidus, Heterocephalacria septentrionalis as endophyte from Cladonia rangiferina, Vishniacozyma phoenicis from dates fruit, Volvariella paludosa from swamp. Slovenia, Mallocybe crassivelata on soil. South Africa, Beltraniella podocarpi, Hamatocanthoscypha podocarpi, Coleophoma podocarpi and Nothoseiridium podocarpi (incl. Nothoseiridium gen. nov.) from leaves of Podocarpus latifolius, Gyrothrix encephalarti from leaves of Encephalartos sp., Paraphyton cutaneum from skin of human patient, Phacidiella alsophilae from leaves of Alsophila capensis, and Satchmopsis metrosideri on leaf litter of Metrosideros excelsa. Spain, Cladophialophora cabanerensis from soil, Cortinarius paezii on soil, Cylindrium magnoliae from leaves of Magnolia grandiflora, Trichophoma cylindrospora (incl. Trichophoma gen. nov.) from plant debris, Tuber alcaracense in calcareus soil, Tuber buendiae in calcareus soil. Thailand, Annulohypoxylon spougei on corticated wood, Poaceascoma filiforme from leaves of unknown Poaceae. UK, Dendrostoma luteum on branch lesions of Castanea sativa, Ypsilina buttingtonensis from heartwood of Quercus sp. Ukraine, Myrmecridium phragmiticola from leaves of Phragmites australis. USA, Absidia pararepens from air, Juncomyces californiensis (incl. Juncomyces gen. nov.) from leaves of Juncus effusus, Montagnula cylindrospora from a human skin sample, Muriphila oklahomaensis (incl. Muriphila gen. nov.) on outside wall of alcohol distillery, Neofabraea eucalyptorum from leaves of Eucalyptus macrandra, Diabolocovidia claustri (incl. Diabolocovidia gen. nov. ) from leaves of Serenoa repens, Paecilomyces penicilliformis from air, Pseudopezicula betulae from leaves of leaf spots of Populus tremuloides. Vietnam, Diaporthe durionigena on branches of Durio zibethinus and Roridomyces pseudoirritans on rotten wood. Morphological and culture characteristics are supported by DNA barcodes.

Globally, fungal pathogens cause enormous crop losses and current control practices are not always effective, economical or environmentally sustainable. Tools enabling genetic management of wild pathogen populations could potentially solve many problems associated with plant diseases. A natural gene drive from a heterologous species can be used in the globally important cereal pathogen Fusarium graminearum to remove pathogenic traits from contained populations of the fungus. The gene drive element became fixed in a freely crossing population in only three generations. Repeat-induced point mutation (RIP), a natural genome defence mechanism in fungi that causes C to T mutations during meiosis in highly similar sequences, may be useful to recall the gene drive following release, should a failsafe mechanism be required. We propose that gene drive technology is a potential tool to control plant pathogens once its efficacy is demonstrated under natural settings.

Summary Globally, fungal pathogens cause enormous crop losses and current control practices are not always effective, economical or environmentally sustainable. Tools enabling genetic management of wild pathogen populations could potentially solve many problems associated with plant diseases. A natural gene drive from a heterologous species can be used in the globally important cereal pathogen, Fusarium graminearum , to remove pathogenic traits from contained populations of the fungus. The gene drive element became fixed in a freely crossing populations in only three generations. Repeat induce point mutation, a natural genome defence mechanism in fungi, may be useful to recall the gene drive following release, should a failsafe mechanism be required. We propose that gene drive technology is a potential tool to control plant pathogens.

Fungal plant pathogens are increasingly recognised as being among the most effective and safe agents in classical weed biological control programs worldwide. Suitability of the rust fungus P. rapipes as a classical biological control agent for Lycium ferocissimum (African boxthorn) in Australia was assessed using a streamlined agent selection framework. Studies with P. rapipes were undertaken to elucidate its life cycle, confirm its taxonomic placement and determine its pathogenicity to L. ferocissimum and seven closely-related Solanaceae species that occur in Australia. Field surveys in the native range of South Africa, experiments in a containment facility in Australia and DNA sequencing confirmed that P. rapipes is macrocyclic and autoecious, producing all five spore stages on L. ferocissimum. The stages not previously encountered, spermogonia and aecia, are described. Sequencing also confirmed that P. rapipes is sister to Puccinia afra, in the 'Old World Lineage' of Puccinia species on Lycieae. Two purified isolates of the fungus, representing the Eastern and Western Cape distributions of P. rapipes in South Africa, were cultured in the containment facility for use in pathogenicity testing. L. ferocissimum and all of the Lycium species of Eurasian origin tested ‒ Lycium barbarum (goji berry), Lycium chinense (goji berry 'chinense') and Lycium ruthenicum (black goji berry) - were susceptible to both isolates of P. rapipes. The Australian native L. australe and three more distantly related species in different genera tested were resistant to both isolates. The isolate from the Western Cape was significantly more pathogenic on L. ferocissimum from Australia, than the Eastern Cape isolate. Our results indicate that P. rapipes may be sufficiently host specific to pursue as a biological control agent in an Australian context, should regulators be willing to accept damage to the Eurasian goji berries being grown, albeit to a limited extent, in Australia.

Isolations from oak symptomatic of Acute Oak Decline, alder and walnut log tissue, and buprestid beetles in 2009-2012 yielded 32 Gram-negative bacterial strains showing highest gyrB sequence similarity to Rahnella aquatilis and Ewingella americana. Multilocus sequence analysis (using partial gyrB, rpoB, infB and atpD gene sequences) delineated the strains into six MLSA groups. Two MLSA groups contained reference strains of Rahnella genomospecies 2 and 3, three groups clustered within the Rahnella clade with no known type or reference strains and the last group contained the type strain of E. americana. DNA-DNA relatedness assays using both the microplate and fluorometric methods, confirmed that each of the five Rahnella MLSA groups formed separate taxa. Rahnella genomospecies 2 and 3 were previously not formally described due to a lack of distinguishing phenotypic characteristics. In the present study, all five Rahnella MLSA groups were phenotypically differentiated from each other and from R. aquatilis. Therefore we propose to classify the strains from symptomatic oak, alder and walnut and buprestid beetles as: Rahnella victoriana sp. nov. (type strain FRB 225(T)=LMG 27717(T)=DSM 27397(T)), Rahnella variigena sp. nov. (previously Rahnella genomosp. 2, type strain CIP 105588(T)=LMG 27711(T)), Rahnella inusitata sp. nov. (previously Rahnella genomosp. 3, type strain DSM 30078(T)=LMG 2640(T)), Rahnella bruchi sp. nov. (type strain FRB 226(T)=LMG 27718(T)=DSM 27398(T)) and Rahnella woolbedingensis sp. nov. (type strain FRB 227(T)=LMG 27719(T)=DSM 27399(T)).

In 2010, cream-coloured, Gram-negative staining, facultatively anaerobic enterobacteria were isolated from a single black oak tree (Quercus kelloggii) exhibiting decline symptoms in southern California, USA. These 12 isolates were tentatively identified as Gibbsiella quercinecans based on partial gyrB sequencing. Closer examination of the strains using multilocus sequence analysis, based on partial sequences of gyrB, rpoB, infB and atpD genes, and almost complete 16S rRNA gene sequencing suggested that the isolates belong to a novel taxon within the genus Gibbsiella with G. quercinecans as their closest phylogenetic relative. DNA-DNA relatedness studies confirmed that the strains belong to a single taxon in Gibbsiella, which can be differentiated from other members of the genus by several phenotypic traits. Therefore, the name Gibbsiella greigii sp. nov. is proposed for this novel species isolated from symptomatic Q. kelloggii in the USA with FRB 224(T) (=LMG 27716(T)=NCPPB 4583(T)) as the type strain.

Summary Between 2008 and 2011, severe dieback associated with root and collar rot was reported on A rbutus unedo in several sites in S ardinia, I taly. Isolations from infected tissues and rhizosphere soil samples consistently yielded a P hytophthora species. It was initially identified as P hytophthora cinnamomi var. parvispora K röber and Marwitz by comparing morphological features with the original description and the internal transcribed spacer ( ITS ) sequences with those present in G en B ank. A multigene phylogeny based on DNA sequence data from two nuclear ( ITS and β‐tubulin) and two mitochondrial ( cox 1 and cox 2) gene regions combined with extensive morphological and physiological properties of these isolates, including the ex‐type culture of P . cinnamomi var. parvispora , demonstrates that this taxon is unique and it is redesignated here as P hytophthora parvispora sp. nov. Although morphologically similar to P . cinnamomi , P . parvispora differs by its smaller‐sized sporangia, chlamydospores, oogonia and oospores, higher oospore wall index, single‐celled antheridia, higher minimum and maximum temperatures for growth and faster growth at optimum temperature. In the phylogeny, P . parvispora falls within P hytophthora ITS clade 7a, grouped in a well‐supported clade sister to P . cinnamomi . In pathogenicity tests, P . parvispora and P . cinnamomi were equally aggressive towards A . unedo seedlings. The possible geographic origin of P . parvispora is also discussed.

Gram-negative, facultatively anaerobic bacteria were isolated from symptomatic oak tissue in the UK and USA. Partial gyrB sequencing placed ten strains in the genus Brenneria, with B. goodwinii as the closest phylogenetic relative. The strains were investigated further using a polyphasic approach including MLSA (based on partial gyrB, rpoB, infB and atpD gene sequences), 16S rRNA gene sequencing, DNA–DNA relatedness studies and both phenotypic and chemotaxonomic assays. The MLSA and 16S rRNA gene analyses separated the strains into two groups based on origin, suggesting that they belong to Brenneria as two novel species. However, the DNA–DNA relatedness values revealed a closer relationship between the groups and indicated that they should belong to the same species. As the two groups of strains from the UK and USA can be differentiated from each other phenotypically and by ERIC PCR fingerprints, it is proposed to classify them as novel subspecies of a novel Brenneria species. The name Brenneria roseae sp. nov. (FRB 222T=LMG 27714T=NCPPB 4581T) is proposed, with Brenneria roseae subsp. roseae ssp. nov. (FRB 222T=LMG 27714T=NCPPB 4581T) for the strains from the UK and Brenneria roseae subsp. americana ssp. nov. (FRB 223T=LMG 27715T=NCPPB 4582T) for the strains from the USA.

Pseudocercospora is a large cosmopolitan genus of plant pathogenic fungi that are commonly associated with leaf and fruit spots as well as blights on a wide range of plant hosts. They occur in arid as well as wet environments and in a wide range of climates including cool temperate, sub-tropical and tropical regions. Pseudocercospora is now treated as a genus in its own right, although formerly recognised as either an anamorphic state of Mycosphaerella or having mycosphaerella-like teleomorphs. The aim of this study was to sequence the partial 28S nuclear ribosomal RNA gene of a selected set of isolates to resolve phylogenetic generic limits within the Pseudocercospora complex. From these data, 14 clades are recognised, six of which cluster in Mycosphaerellaceae. Pseudocercospora s. str. represents a distinct clade, sister to Passalora eucalypti, and a clade representing the genera Scolecostigmina, Trochophora and Pallidocercospora gen. nov., taxa formerly accommodated in the Mycosphaerella heimii complex and characterised by smooth, pale brown conidia, as well as the formation of red crystals in agar media. Other clades in Mycosphaerellaceae include Sonderhenia, Microcyclosporella, and Paracercospora. Pseudocercosporella resides in a large clade along with Phloeospora, Miuraea, Cercospora and Septoria. Additional clades represent Dissoconiaceae, Teratosphaeriaceae, Cladosporiaceae, and the genera Xenostigmina, Strelitziana, Cyphellophora and Thedgonia. The genus Phaeomycocentrospora is introduced to accommodate Mycocentrospora cantuariensis, primarily distinguished from Pseudocercospora based on its hyaline hyphae, broad conidiogenous loci and hila. Host specificity was considered for 146 species of Pseudocercospora occurring on 115 host genera from 33 countries. Partial nucleotide sequence data for three gene loci, ITS, EF-1α, and ACT suggest that the majority of these species are host specific. Species identified on the basis of host, symptomatology and general morphology, within the same geographic region, frequently differed phylogenetically, indicating that the application of European and American names to Asian taxa, and vice versa, was often not warranted.

Cryphonectria parasitica has moved north into many European countries since it was first seen in Italy in the 1930's (Biraghi, 1; Robin & Heiniger, 4). In November 2011, approximately 90 dead or cankered Castanea sativa (sweet chestnut) trees were observed on a farm in Warwickshire, England. The trees had come from a French nursery in 2007 and been planted, together with Juglans nigra (walnut) and Corylus avellanus (hazel) on a 1.63 ha site. Since then many of the sweet chestnut had not grown well and some had died. Subsequent replanting took place in 2010 with planting stock originating from the same French nursery. Diseased trees exhibited crown dieback, sunken cankers, cracked bark above the root collar and in some cases orange coloured fungal sporulation was visible on the bark (Fig. 1). Samples were collected from five affected trees and symptom-bearing bark pieces then placed in moist chambers at 18°C for up to 10 days to induce fungal sporulation. Cultures were made from spore masses extruding from the cankered bark onto potato dextrose agar (PDA). Isolations were also made onto PDA from the edge of necrotic lesions visible in the phloem tissue of cankered bark tissue. Fungal cultures were obtained from four of the five trees and the causal fungus was identified through morphological characteristics and DNA sequence data. DNA was extracted using the CTAB extraction protocol (Möller et al., 3) and a portion of the ITS rDNA operon amplified and sequenced following the method of Gryzenhout et al., (2). Resulting sequences were blasted against the nucleotide sequence database of the National Center for Biotechnology Information (NCBI) and closely allied sequences downloaded from NCBI and used to generate a DNA sequence phylogeny (Fig. 2). The DNA sequences of isolates collected in this study were very similar to many C. parasitica sequences found on GenBank including AY141859 (99% coverage, 99% identity) and JN942325 (100% coverage, 99% identity). This identification was corroborated by morphological characteristics of the isolated fungus which were the same as those described for Cryphonectria parasitica (Sivanesan & Holiday, 5). Ascospores and asci of the C. parasitica isolates collected in England measured (7.5-)8-10(-12) x (3-)4(-5) μm and (32-)38-45(-48) x (5-)6-8(-9) μm respectively, which are in the range known for this species (Sivanesan & Holliday, 5) (Fig. 3). Pathogenicity of C. parasitica was confirmed through Koch's postulates. Mycelial plugs from three seven-day-old C. parasitica cultures were used to inoculate detached twigs of C. sativa, while controls used sterile PDA. Each inoculation was carried out in triplicate and inoculated twigs were incubated at 20°C for 5 weeks in a 9h/15 h light/dark cycle following which lesions were measured (Fig. 4). Cryphonectria parasitica was re-isolated from lesions confirming the pathogenicity of these isolates. This finding represents an example of incursion by an exotic pathogen into the UK and highlights the importance of plant health inspections and the difficulty of detecting infected plant material at the time of importation. Strategies are underway to manage and contain this outbreak while surveys are being conducted to determine if other sites have infected trees. © Crown copyright 2013. Published under the Open Government Licence.