An Overview of Phytophthora Species on Woody Plants in Sweden and Other Nordic Countries

The genus Phytophthora, with 326 species in 12 phylogenetic clades currently known, includes many economically important pathogens of woody plants. Different Phytophthora species often possess a hemibiotrophic or necrotrophic lifestyle, have either a broad or narrow host range, can cause a variety of disease symptoms (root rot, damping-off, bleeding stem cankers, or blight of foliage), and occur in different growing environments (nurseries, urban and agricultural areas, or forests). Here, we summarize the available knowledge on the occurrence, host range, symptoms of damage, and aggressiveness of different Phytophthora species associated with woody plants in Nordic countries with a special emphasis on Sweden. We evaluate the potential risks of Phytophthora species to different woody plants in this geographical area and emphasize the increasing threats associated with continued introduction of invasive Phytophthora species.

Understanding how best to engage recreationists in biosecurity to reduce the impacts of tree diseases: a review

Pests and diseases introduced from other countries are known to pose a threat to trees, woods and forests in many locations throughout the world. Once introduced they can be spread inadvertently by countryside visitors hiking, biking or riding along paths and trails through wooded areas. Engaging and communicating with these groups of countryside users to encourage and facilitate positive biosecurity behaviours is crucial for the future resilience of trees, woods and forests. This review draws on literature outlining principles for stakeholder engagement in forestry as well as evaluations of biosecurity campaigns from around the world. Key points are briefly presented for communicators aiming to encourage better biosecurity in the countryside. These include, the need to design campaigns based on the values and motivations of recreationists, using trusted information sources and understanding the importance of combining information with facilities so as to reduce the cost (in terms of effort and inconvenience) to hikers and other countryside users.

Pest categorisation of Gremmeniella abietina

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a pest categorisation of Gremmeniella abietina, a well-defined species and distinguishable fungus of the family Godroniaceae. The species G. abietina includes several varieties, races and biotypes that are found in different geographical locations, on different hosts and that vary in aggressiveness. The pathogen causes diseases on Pinus species and other conifers such as Abies spp., Picea spp., Larix spp. and Pseudotsuga spp. known as Scleroderris canker in North America and Brunchorstia dieback in Europe. G. abietina has been reported from 19 EU Member States, without apparent ecoclimatic factors limiting establishment. The pathogen is a protected zone (PZ) quarantine pest (Annex IIB) for Ireland and the UK (Northern Ireland). The main European hosts are widespread throughout most of the EU and have been frequently planted in the PZ. The main means of spread are wind-blown ascospores, rain-splashed conidia, plants for planting and traded Christmas trees. Given that G. abietina is most damaging to species that are grown towards the limit of their range, impacts can be expected in the PZ, should the pathogen be introduced there. Risk reduction options include selection of disease-free planting material, nursery inspections, selection of planting sites at some distance from infested plantations, appropriate spacing between plants and thinning. The main uncertainties concern the indeterminate endophytic stage of the fungus, the pathogen distribution and the future taxonomic status of G. abietina, given its intraspecific diversity. All the criteria assessed by the Panel for consideration as potential PZ quarantine pest are met. The criterion of plants for planting being the main pathway for spread for regulated non-quarantine pests is not met: plants for planting are only one of the means of spread of the pathogen.

IMA Genome-F 7: Draft genome sequences for Ceratocystis fagacearum, C. harringtonii, Grosmannia penicillata, and Huntiella bhutanensis

Draft genomes for the fungi Ceratocystis fagacearum, C. harringtonii, Grosmannia penicillata, and Huntiella bhutanensis are presented. Ceratocystis fagacearum is a major causal agent of vascular wilt of oaks and other trees in the family Fagaceae. Ceratocystis harringtonii, previously known as C. populicola, causes disease in Populus species in the USA and Canada. Grosmannia penicillata is the causal agent of bluestain of sapwood on various conifers, including Picea spp. and Pinus spp. in Europe. Huntiella bhutanensis is a fungus in Ceratocystidaceae and known only in association with the bark beetle Ips schmutzenhorferi that infests Picea spinulosa in Bhutan. The availability of these genomes will facilitate further studies on these fungi.

An overview of Australia's Phytophthora species assemblage in natural ecosystems recovered from a survey in Victoria

Although Phytophthora species cause serious diseases worldwide, until recently the main focus on disease in natural ecosystems in southern Australia has been on the distribution and impact of P. cinnamomi. However, new Phytophthora pathogens have emerged from natural ecosystems, and there is a need to better understand the diversity and distribution of these species in our natural forests, woodlands and heathlands. From a survey along a 70 km pipeline easement in Victoria, Phytophthora species were isolated from 249 rhizosphere samples and 25 bait bags deployed in 21 stream, river, or wetland locations. Of the 186 Phytophthora isolates recovered, 130 were identified to species based on ITS sequence data. Ninety-five isolates corresponded to 13 described Phytophthora species while additionally 35 isolates were identified as Clade 6 hybrids. Phytophthora cinnamomi was the most common species isolated (31 %), followed by P. elongata (6 %), both species were only recovered from soil. Samples from sites with the highest soil moisture at the time of sampling had the highest yield of isolates. Consistent with other studies throughout the world, Clade 6 species and their hybrids dominated water samples, although many of these species were also recovered less frequently from soil samples. Many of the species recovered in this study have not previously been reported from eastern Australia, reinforcing that Phytophthora species are widespread, abundant and diverse in natural ecosystems. We have probably been underestimating Phytophthora diversity in Australia.

Disruption of the 'disease triangle' by chemical and physical environmental change

The physical and chemical environment of the Earth has changed rapidly over the last 100 years and is predicted to continue to change into the foreseeable future. One of the main concerns with potential alterations in climate is the propensity for increases in the magnitude and frequency of extremes to occur. Even though precipitation is predicted to increase in some locations, in others precipitation is expected to decrease and evapotranspiration increase with air temperature, resulting in exacerbated drought in the future. Chemical [ozone (O3 ) and other air contaminants] and subsequent physical alterations in the environment will have a profound effect on the 'disease triangle' (a favourable environment, a susceptible host and a virulent pathogen) and should be included in any analysis of biological response to climate change. The chemical and physical environment affects plant health and alters plant susceptibility to insect and pathogen attack through increased frequency, duration and severity of drought and reduction in host vigour. The potential effects of climate change and O3 on tree diseases with emphasis on the western United States are discussed. We describe a generalised modelling approach to incorporate the complexities of the 'disease triangle' into dynamic vegetation models.