The spotted wing drosophila Drosophila suzukii is a fruit fly native to Eastern Asia that was accidentally introduced to the Americas and Europe. Because this fly is able to attack undamaged ripening fruits, it became a major problem for fruit growers such as the cherry industry, but also wild fruit-bearing trees and shrubs. For the country-wide and long-term control of the fruit fly, the importation from Asia and release of the parasitoid wasp Ganaspis brasiliensis has been repeatedly suggested. However, uncertainty about the identity and specificity of the parasitoid has so far prevented its use for biological control in Europe.

We used a combination of molecular analyses and laboratory experiments to gather evidence that the parasitoid wasp Ganaspis brasiliensis is in fact a complex of at least two species. Individuals from one genetic group (called G3) readily parasitize several species of native drosophila fruit flies, which have important ecological functions. But individuals from the other group (called G1) are specific to D. suzukii larvae feeding on ripening fruits. Because only the invasive spotted wing drosophila attacks ripening fruits, parasitoids from the G1 group appear to be specific to the target pest and therefore well suited for biological control.

Decision-makers and biological control practitioners should consider that while the parasitoid wasps are still called the same and cannot be distinguished by their appearance, important genetic and behavioral differences exist, making especially G1 Ganaspis brasiliensis suitable and safe for biological control against the spotted wing drosophila.

Ceratocystis platani causes canker stain of plane tree and is a serious disease of Platanus spp. in both the United States and Europe. Current chemical or biological methods are not effective in controlling C. platani. Therefore new preventive methods must be developed to limit the spread of this pathogen. We characterized the main volatile organic compounds (VOC) emitted in vitro by pure cultures of C. platani and other common fungal pathogen species of hosts plants growing in the same ecosystems as plane trees. We found that C. platani emitted a similar blend of VOCs as the phylogenetically closed C. populicola. In particular, C. platani was characterized by the emission of isoamyl acetate and isobutyl acetate while C. populicola by ethyl acetate and isobutyl acetate, which were not released by any of the other fungal species grown on the same medium. Furthermore, following a targeted approach based on the main VOCs found in vitro, we were able to validate in vivo that VOCs uniquely emitted by C. platani (i.e. isobutyl acetate along with isoamyl alcohol) were released from the bark of plane trees after C. platani inoculation. Our results demonstrate the possibility of exploiting VOC emitted specifically by C. platani as biomarkers to recognize plane trees infected by this pathogen. We are now looking for technical applications of the results in order to detect the presence of infected seedlings in the ports of entry.

With increasing forest insect damage caused by climate change and biological invasions, effective preventive control methods are needed. Using a meta-analysis of ca. 600 case studies, we show that a given insect species inflicts, on average, 20% less damage on a given tree species in mixed forest stands than in pure stands. This species-mixing resistance was significant for different types of pest diets, from wood boring pests to leaf-eating insects. It was more notable for specialist insect pests (about -40% damage) than for polyphagous ones. It also increased with the phylogenetic diversity of the species in the mixture, being more important in the coniferous - deciduous species mixtures. The main reasons for the better resistance of mixed forests are the pests’ reduced ability to locate and infect host trees surrounded by non-host trees and a greater abundance of natural enemies. The species’ spatial arrangement within the mixed forest is also important. An intimate (tree-by-tree) species mixing scheme is the most efficient. However, it is more difficult to manage in mechanized production forests such as planted forests. An interesting alternative for mixed-species plantations is the row-wise intermingling pattern, as it allows differentiated silviculture while maintaining close proximity between the different tree species. Finally, a solution with less impact on forest managers is the establishment of mixed hedges surrounding a pure stand of the focal species.

Processionary caterpillars from Australia and Europe, Ochrogaster lunifer and Thaumetopoea pityocampa respectively, are social insects that live in semi-urban and rural environments near humans and domestic animals. Both species are tree defoliators expanding their natural range. They also carry millions of microscopic urticating hairs on abdominal segments which can easily be dispersed by wind and spread throughout the environment. Contact with such hairs in vertebrates, especially mammals and humans, can cause various inflammatory issues and allergy problems. The highest risk for humans and animals encountering these processionary caterpillars is commonly March to May every year, when caterpillars form a procession to locate a new host after defoliating the initial host and when they leave the nest to find a pupation site underground. O. lunifer and T. pityocampa processions travel on average 40 and 16 m per day from the infested tree, respectively. O. lunifer caterpillars procession towards shaded areas, whereas T. pityocampa move towards well-lit areas. With this information, we can forewarn people to avoid infested areas or stay at least 80 m and 30 m away from host trees with O. lunifer and T. pityocampa nests respectively, during the procession period. Protective clothing and eyewear are recommended if people are attending these areas of high concern.

Tree pandemics are a major cause of economic and ecological loss in forest and urban ecosystems. They often depend on the introduction of a non-native pathogen, which is occupying the niche of a native, non-aggressive organism.

Three major pandemics of forest and urban trees in European ecosystems are considered: the Dutch elm disease, the cypress canker, and the pine wilt disease.

Results suggest that these pandemics rely on the introduction of a non-native pathogen that exploits well-developed interactions between native non-aggressive organisms and insect vectors associated with trees. The success of the invaders depends on the morphological, physiological and behavioural proximity of the players and on the mutual benefits resulting from the associations.

Deciphering such interactions in native systems may help to predict the outcome of the introduction of new pathogens and the development of new tree pandemics. It is recommended to explore carefully the relationships among the organisms in the native ecosystems and to analyse the potential recipient environments. The approach should be included in the pest risk assessment procedures.

An effective framework for early warning and rapid response is a crucial element to prevent or mitigate the impact of biological invasions of tree pathogens, especially at ports of entry. Molecular detection of pathogens by using PCR-based methods usually requires a well-equipped laboratory. Rapid detection tools that can be applied as point-of-care diagnostics are highly desirable, especially to intercept quarantine plant pathogens such as Xylella fastidiosa, Ceratocystis platani and Phytophthora ramorum, three of the most devastating pathogens of trees and ornamental plants in Europe. To this aim, three different LAMP (Loop mediated isothermal amplification) assays able to detect each target pathogen both in DNA extracted infected plant tissues were developed. By using the portable instrument Genie ® II, the LAMP assay was able to recognize X. fastidiosa, C. platani and P. ramorum DNA within 30 minutes of isothermal amplification reaction, with high levels of specificity and sensitivity. These new LAMP-based tools, allowing on-site rapid detection of pathogens, are especially suited for being used at ports of entry, but they can be also profitably used to monitor and prevent the possible spread of invasive pathogens in natural ecosystems or in tree nurseries.

Fusarium circinatum is the causal agent of pitch canker, a lethal disease of pine and other conifers. Since F. circinatum is a quarantine organism, its timely detection could efficiently prevent its introduction in new areas or facilitate its management in already infected sites. In this aim, a sequence-specific probe has been developed and used in a LAMP assay for F. circinatum using a field-deployable portable instrument. The assay was able to recognize the pathogen in host tissues in just 30 minutes and the sensitivity of assay makes it possible to detect even small amounts of F. circinatum DNA. The high specificity and efficiency of this method suggests its use as a standard diagnostic tool during phytosanitary controls.

The Caliciopsis canker on pines is caused by Caliciopsis pinea , In Europe, the disease has only occasionally been reported causing cankers, mostly on Pinus radiata in stressed plantations. The aim of this study was to clarify the taxonomy of Caliciopsis specimens collected from infected Pinus spp. in Europe to improve their detection and identification . The pathogenicity of the fungus was also considered. Two distinct species were identified based on morphology and multilocus phylogenetic analyses: Caliciopsis pinea that occurs in North America and a morphologically similar but phylogenetically distinct species described here as Caliciopsis moriondi sp. nov., found in Europe. The correct identification of the pathogen species is fundamental in case of need of regulation.

Insects are one of the most successful groups of non-native invasive species, and the number of new introductions has been increasing in the last decades. Insect invasions are favored mainly by the increase in international trade, as most of them travel across the world inside shipping containers. For this reason, the interception of hitchhiker insects transported inside containers is one of the most important actions to prevent the introduction of new alien species. The effectiveness of sticky light traps was tested for the interception of pests inside the containers during shipment using four model species: Cadra cautella (Lepidoptera: Pyralidae), Drosophila melanogaster (Diptera: Drosophilidae), Sitophilus zeamais and Ips typographus (Coleoptera: Curculionidae). This trap consists in a carton box made attractive by a white LED light powered by a long-life AA battery. We found that light has a positive effect for the capture of C. cautella and D. melanogaster: in fact, activated traps (with light on) captured significantly more than control traps (with light off). Moreover, the number of captures for these two species was similar in both empty and full containers. Instead, Coleoptera (S. zeamais and I. typographus) were rarely caught, probably because of their ability to escape from traps. Finally, results show that increasing trap density in the container (from 1 to 8) increases the probability of insect capture. Given the results, we conclude that sticky light traps can be an effective tool for the early-detection of alien insect species travelling inside container, but they need some improvements. We suggest increasing the effectiveness of the trap by adding a stronger glue to reduce insect escape from traps. Finally, another possible improvement deals with the use of different color lights (i.e. wavelength) that can increase the attractiveness of the trap to a larger number of species.

A massive urban forestry project has been initiated and will eventually cover over 600 km2 by 2030, providing 30% forest cover in a 2000 km2 area 120 km southwest of Beijing in a new development zone called the Xiongan New Area (XNA), which will serve as the second capital of China. 100 km2 have been already planted in a network of parks and landscaped green areas. Using science to inform policy, one major goal of the tree planting program was to make urban forests more resistant and resilient to potential invasive species threats. To accomplish this best management practice, planted tree species were carefully selected, existing established pests were delineated, and potential new forest invasive species of concern threatening the new area were identified. The framework for the invasive pests management strategy was based on a “big data” approach, with each tree receiving a QR code to facilitate real time monitoring and mapping of pests and diseases, coupled with a decision system to implement appropriate control methods. This new approach to urban forestry has the potential to become an exemplary model for urban forestry planning, by integrating forest health surveys and pest control operations with sustainable forestry management.

HOMED conducted a survey of more than 240 practitioners across Europe to learn more about their practices and needs in terms of tools and methods for the detection and identification of invasive forest pests and pathogens.

They suggested developing or improving the following methods of surveillance:

- Broad-spectrum traps to detect non-native insect pests in containers transporting live plants or wood packaging

- Drones to monitor forest defoliation.

- Smartphone applications and citizen science programmes to help detect new invasive pest of pathogens on trees (incl. in urban settings)

- Posters informing a wide audience of the risks of transporting tree pest contaminated material in airport lobbies and garden centers.

- Continuous training of personnel in charge of forest surveillance on new detection and identification techniques.

They suggested developing or improving the following methods of management:

- Use of locally sourced trees and tree seeds to avoid imports.

- Use of quarantine areas for imported plants for planting.

- Reinforced inspection of exported trees, imported trees and newly planted trees.

- Development of mixed species forests that are more resistant to invasion

- Fumigation procedure of imported potted trees, according to local legislation.