Invasive alien species (IAS) are an important threat to forests. One of the best ways to manage potential IAS is through early detection and rapid response (EDRR) strategies. However, when dealing with IAS in forests, EU regulations are divided between phytosanitary regulations and IAS regulations. A version of EDRR for the former has been in place in the EU for more than 15 years while the latter is still in the process of being implemented. During 2019, a workshop was held to gather international experts on different plant health pests and IAS. The purpose of this workshop was to identify the opportunities and difficulties in applying the EDRR system in the EU phytosanitary and IAS legislation to four species for providing suggestions to improve the EDRR system. The model species are well known and come from different trophic levels. These species were the American pokeweed (Phytolacca americana), the grey squirrel (Sciurus carolinensis); and the plant health pests Geosmithia morbida and Emerald ash borer (Agrilus planipennis). We identified the similarities in the challenges of early detection, rapid response and communication of these species. For all species, difficulties in species identification, knowledge gaps on the pathways of spread, a lack of resources and uncertainty over which national government service was the competent authority were identified as the main challenges. Other challenges like public perception for the grey squirrel or methodological problems were species-specific. Regarding the rapid response: public perception, determination of the eradication area, sufficient scientific capacity and the lack of resources were common challenges for all species. Therefore, collaboration between institutes dealing with plant health pests and IAS can lead to better control of both groups of unwanted organisms in forests.

Presence of invasive alien plant species in urban areas has become an issue throughout the globe. City administrations are making efforts to avoid invasions, to eradicate and/or control invasive species, or alternatively, try to process them into useful products. To monitor the spread of species over a region, it is important to map invasive species. In the scope of the APPLAUSE project, we have developed a One-Class support vector machine (SVM) approach to detect invasive species from individual aerial and multiple Sentinel-2 satellite images over the City of Ljubljana (Slovenia). In this paper, we focus specifically on the detection of Japanese knotweed, because it produces large stands and is therefore the most detectable invasive species in the studied area. The proposed SVM approach uses red-green-blue (RGB) band composites and infrared (IR) bands as input data for aerial images, while for satellite images additionally normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) are used. In the study, we used ground truth data collected by experts both as training and as validation data. On aerial images, we first perform segmentation, which is followed by two One-Class SVM classifications. On these classification outputs, we use K-means algorithm on the IR band, which groups the samples and removes the ones that were falsely recognized as Japanese knotweed. Merging the results together and masking out small samples and areas where Japanese knotweed is not present, we get the final result. On satellite data the approach is similar; the only difference is the usage of multiple input images from different acquisition dates for SVM classification. For detection of Japanese knotweed from the aerial images the accuracy was 83%, and 90% for stands larger than 100 m2 on satellite data. The results demonstrate that the applied methodology with the qualitative ground truth data can be used operationally for automatic detection of Japanese knotweed on the municipality level.

A multi-lure approach for trapping a wide variety of Cerambycidae was tested at the Port of Vienna in 2017 and 2018, a high risk area for the introduction of invasive tree pests transported in wood packaging material. Traps were deployed in the port area and in an adjacent broadleaved forest. A second experimental site was set up in a pine forest in eastern Austria not influenced by wood imports. Blends of cerambycid pheromone compounds were tested: Blend 1 mixing four pheromone components for various Lamiinae and Spondylidinae, Blend 2 mixing four pheromone components for various Cerambycinae and Prioninae, and Blend 3 combining the eight volatiles. Additionally, the host tree kairomones ethanol and (-)-α-pinene were added as general attractants. A total of 30 cerambycid species was detected with the traps in 2017; 36 species were detected in 2018. The full blend (Blend 3 plus ethanol plus (-)-α-pinene) caught significantly more cerambycid species than the more specific Blends 1 and 2. Addition of ethanol plus (-)-α-pinene to Blend 3 significantly increased the number of trapped cerambycid individuals but not the number of species. Overall, we caught 28 cerambycid species at the Port of Vienna (11 species) and the adjacent forest (23 species) and 23 species in the pine forest. No alien cerambycid was detected in the two years. Trapping with multiple lures could be employed in surveillance programs against potentially invasive cerambycids in high risk areas for introduction.

Widespread and locally severe foliar symptoms resembling Dothistroma Needle Blight (DNB), one of the most important infectious diseases of forest trees worldwide, were recently observed in La Sila Massif, a mountain plateau covered with native forests of Pinus nigra subsp. laricio in La Sila National Park, Southern Italy. At the same time, DNB symptoms were observed in Pinus cembra and Pinus mugo forests in the Paneveggio-Pale di San Martino Nature Park and in Val Sarentino, Northeastern Italy. Defoliation was extensive at all sites and severe on the majority of plants of affected species, both adult trees and renovation. In particular on Pinus cembra, the disease was so serious as to locally threaten the species’ reproduction and survival, an unusually heavy damage on this host. Species-specific real time PCR diagnostics, recommended by EPPO, was applied to needle samples from these sites and the presence of Dothistroma septosporum was ascertained, while Dothistroma pini, the morphologically identical congeneric species causing the same disease, was not detected. The pathogen was isolated from conidiomata and species attribution was confirmed by sequencing of the ITS region. In addition, a culture independent survey based on the same molecular assays was carried out in other areas of Northern, Central and Southern Italy, where pines of various species were affected by similar symptoms, and gave negative results for both Dothistroma species. Results show that D. septosporum currently has in Italy a much larger distribution and host range than reported and is associated to life-threatening damage to native pine species growing in established populations for in situ conservation of genetic resources, which would require an update of specific conservation actions.

The trees and forests of Europe are increasingly under threat from new pests and diseases that have originated in other parts of the world. Early detection of alien species when they first appear in European countries allows rapid response and offers the best chance to mitigate against their establishment and spread. Citizen science initiatives such as LIFE ARTEMIS in Slovenia, and Observatree in the UK, provide members of the public with the necessary training and educational resource to identify these tree pests and diseases and report them to the appropriate authorities, thereby increasing the level of surveillance and the capacity of the early warning system. This paper summarises some of the outcomes of these two projects and how they have both become integral parts of the official forest and tree health monitoring systems within their respective countries of Slovenia and the United Kingdom.

The early detection of tree health pests and disease is an important component of biosecurity to protect the aesthetic, recreational and economic importance of trees, woodlands and forestry. Citizen science is valuable in supporting the early detection of tree pests and diseases. Different stakeholders (government, business, society and individual) will vary in their opinion of the balance between costs and benefits of early detection and consequent management, partly because many costs are local whereas benefits are felt at larger scales. This can create clashes in motivations of those involved in citizen science, thus leading to ethical dilemmas about what is good and responsible conduct for the use of citizen science. We draw on our experience of tree health citizen science to exemplify five dilemmas. These dilemmas arise because: the consequences of detection may locally be severe (e.g. the destruction of trees); knowledge of these impacts could lead to refusal to make citizen science reports; citizen science reports can be made freely, but can be costly to respond to; participants may expect solutions even if these are not possible; and early detection is (by definition) a rare event. Effective engagement and dialogue across stakeholders, including public stakeholders, is important to properly address these issues. This is vital to ensure the public’s long-term support for and trust in the use of citizen science for the early detection of tree pests and diseases.

Horticulture is an important source of alien plant species that could potentially escape the garden fence, survive in nature, reproduce abundantly and finally became harmful to natural ecosystems (i.e. invasive). Additionally, residential garden owners promote the invasion of alien species by dumping garden waste in nature. A surprisingly high number of garden waste deposits was found in lowland peri-urban forest fragments in NE Slovenia. A positive relationship between proximity to these deposits and the number of alien plant species originative from discarded plants has been observed. This fact encouraged us to assess public knowledge of and opinions about invasive alien plant species (IAP), the public’s habits in managing garden waste disposal and thus their awareness of promoting invasions. We conducted a questionnaire-based survey shared among various interest groups on social media platforms in Slovenia. Our results showed relatively good knowledge among respondents about IAPs. Over half the respondents were able to list at least one IAP. The most frequently listed IAP was Ambrosia artemisiifolia, followed by Solidago sp. and Fallopia sp. More than 10% of respondents who own a private residential garden confirmed our assumption that they discarded garden waste in the natural environment – in nearby forests. Respondents who were aware that such an approach could present a possible threat of promoting IAPs were less likely to discard garden waste in forests. According to respondentsʼ socio-demographic status, we hypothesize that overall public awareness of promoting IAPs by discarding garden waste in forests is probably lower than our survey response showed. Findings of this study should be used to improve awareness among the general public about IAPs and possible unintentional introduction paths and dispersal of IAPs, caused by inappropriate garden waste management. In the near future, more activities to improve awareness must be carried out. Our proposal is supported by the opinion of our respondents; 79% of them perceive their knowledge about IAPs as insufficient.

The North American Eastern grey squirrel (Sciurus carolinensis) is a highly invasive mammalian species adversely affecting forest ecosystems worldwide, notably in Europe. The species extirpates sympatric red squirrel (Sciurus vulgaris) populations through resource competition and the spread of pathogenic squirrelpox virus (SQPV) infection. In the United Kingdom (UK), the Red Squirrels United (RSU) project empowered volunteers with the skills, equipment and protocols needed to undertake the proactive detection and subsequent removal of grey squirrels at local, regional and national scales as an aid to red squirrel conservation. The establishment of local volunteer groups to undertake this provided a strong post-project legacy where bespoke local management approaches reflected regional variation in woodland isolation and invasion pathways. Here we highlight valuable lessons for international invasive species management via an adaptive volunteer-based approach to monitoring and control. This included the development of non-invasive techniques to determine the presence of pathological infections in wild squirrels, the provision of evolving approaches to grey squirrel control and where appropriate, red squirrel conservation translocation.