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Planted forests of alien tree species make significant contributions to the economy and provide multiple products and ecosystem services On the other hand, non-native trees now feature prominently on the lists of invasive alien plants in many parts of the world, and in some areas non-native woody species are now among the most conspicuous, damaging and, in some cases, best-studied invasive species. Afforestation and reforestation policies, both on public and private land, need to include clearly stated objectives and principles to reduce impacts of invasive trees outside areas set aside for forestry. With the intention of encouraging national authorities to implement general principles of prevention and mitigation of the risks posed by invasive alien tree species used in plantation forestry into national environmental policies, the Council of Europe facilitated the preparation of a Code of Conduct on Planted Forest and Invasive Alien Trees. This new voluntary Code, comprising 14 principles, complements existing codes of conduct dealing with horticulture and botanic gardens. The Code is addressed to all relevant stakeholders and decision makers in the 47 Member States of the Council of Europe. It aims to enlist the co-operation of the forest sector (trade and industry, national forest authorities, certification bodies and environmental organizations) and associated professionals in preventing new introductions and reducing, controlling and mitigating negative impacts due to tree invasions that arise, directly or indirectly, as a consequence of plantation forestry.
Plant parasitic nematodes (PPN) are known to survive periods of desiccation, an ability that increases the risk of them surviving unintentional transport between countries. To investigate nematode survival in soil subject to prolonged storage, soil collected from a native forest and an organic orchard was stored separately in cupboards at ambient temperature for 36 months. Subsamples were taken at 0, 3, 6, 12, 13, 24 and 36 months to determine the presence of plant parasitic and total nematodes using a standard misting technique. Pratylenchus was used as a model to determine if PPNs that had been under prolonged storage were able to infect plant hosts at 13, 24 and 36 months. Overall, the total number of nematodes recovered from stored soil declined over time, with differences in species diversity determined by molecular methods, related to soil origin. No PPN were recovered in soil stored beyond 13 months using the three-day misting technique. By comparison, Pratylenchus nematodes, using a baiting method, were found to successfully invade host plant roots (ryegrass and white clover) even after 36 months storage and were observed to produce offspring at 13 months. Baiting was not effective for Pratylenchus found in soil originally collected from the forest but was for orchard soil, a result attributed to the lack of suitable host plants for the Pratylenchus species found in forest soil. This study demonstrated, that in protected environments, nematodes could survive for at least 36 months and were observed to produce offspring at 13 months. Baiting with a host plant was more sensitive in detecting nematodes than using the misting extraction technique, although this approach only works where the host plant is known. Without a priori knowledge of the nematode-plant host association, plant baiting may also produce false negatives. In the context of plant biosecurity and providing an accurate risk assessment in soil contaminants, the development of a generic test for PPN that induces nematodes in a resting stage to emerge and respond to a cue would enhance the probability of detection. However, as assessments at the border are often time limited, a molecular based bioassay that can be used to indicate the presence of multiple species of live PPN species may be a more feasible option for risk assessments.