Development of a pathway model to assess the exposure of European pine trees to pine wood nematode via the trade of wood

An Integrated Biosecurity Risk Assessment Model (IBRAM) For Evaluating the Risk of Import Pathways for the Establishment of Invasive Species

An important aspect of analyzing the risk of unwanted organisms establishing in an area is understanding the pathways by which they arrive. Evaluating the risks of these pathways requires use of data from multiple sources, which frequently are uncertain. To address the needs of agencies responsible for biosecurity operations, we present an Integrated Biosecurity Risk Assessment Model (IBRAM) for evaluating the risk of establishment and dispersal of invasive species along trade pathways. The IBRAM framework consists of multiple linked models which describe pest entry into the country, escape along trade pathways, initial dispersal into the environment, habitat suitability, probabilities of establishment and spread, and the consequences of these invasions. Bayesian networks (BN) are used extensively to model these processes. The model includes dynamic BN components and geographic data, resulting in distributions of output parameters over spatial and temporal axes. IBRAM is supported by a web-based tool that allows users to run the model on real-world pest examples and investigate the impact of alternative risk management scenarios, to explore the effect of various interventions and resource allocations. Two case studies are provided as examples of how IBRAM may be used: Queensland fruit fly (Bactrocera tryoni) (Diptera: Tephritidae) and brown marmorated stink bug (Halyomorpha halys) (Hemiptera: Pentatomidae) are unwanted organisms with the potential to invade Aotearoa New Zealand, and IBRAM has been influential in evaluating the efficacy of pathway management to mitigate the risk of their establishment in the country.

Nematodes in the Pine Forests of Northern and Central Greece

Simple Summary

Pine wood nematode Bursaphelenchus xylophilus is the agent of pine wilt disease and one of the most important forest tree pathogens worldwide, transmitted through beetles of the Monochamus genus. As an invasive species, it has spread beyond its natural range by human activity mainly wood trade. The devastating impact it has on pine forests has led to severe environmental and economic damages in its introduced countries. The wide distribution of Monochamus spp. beetles in many parts of the world along with favourable climatic conditions, which are both important factors for the establishment of pine wilt disease, have raised awareness over its continuous expansion. Therefore, in an attempt to control and even inhibit its further spread and consequently its severely adverse impacts, appropriate measures have already been taken and implemented from countries across the globe.

Abstract

In the context of plants or plant products protection by harmful organisms, measures have been taken by EU countries in order to prevent their introduction and establishment into the EU, and also limit their expansion in case they do enter. Such a case is Bursaphelenchus xylophilus (Parasitaphelenchidae, Nematoda), already recorded in Portugal and Spain. So, Member States should take all the appropriate steps in order to monitor and confine if necessary susceptible plants and/or plant products. Such measures include annual surveys even in countries where pine wilt disease does not occur yet. Therefore, national survey programs are widely established, sampling and examining samples from pine trees showing suspicious symptoms that could potentially be attributed to B. xylophilus. In this direction, such a network has also been established in Greece collecting and examining wood samples nationwide. In total, 123 wood samples were collected from conifer trees of Northern and Central Greece. Though B. xylophilus was absent from all samples examined, four other Bursaphelenchus species were identified. In addition, other nematode taxa were also recorded, including several phytophagous, microbivorous as well as predatory nematode species. This highlights the fact that besides preventing the introduction of B. xylophilus in Greece, national survey programs can significantly contribute to and enhance our knowledge of the indigenous nematode species.

Modelling for risk and biosecurity related to forest health

Modelling the invasion and emergence of forest pests and pathogens (PnPs) is necessary to quantify the risk levels for forest health and provide key information for policy makers. Here, we make a short review of the models used to quantify the invasion risk of exotic species and the emergence risk of native species. Regarding the invasion process, models tackle each invasion phase, e.g. pathway models to describe the risk of entry, species distribution models to describe potential establishment, and dispersal models to describe (human-assisted) spread. Concerning the emergence process, models tackle each process: spread or outbreak. Only a few spread models describe jointly dispersal, growth, and establishment capabilities of native species while some mechanistic models describe the population temporal dynamics and inference models describe the probability of outbreak. We also discuss the ways to quantify uncertainty and the role of machine learning. Overall, promising directions are to increase the models’ genericity by parameterization based on meta-analysis techniques to combine the effect of species traits and various environmental drivers. Further perspectives consist in considering the models’ interconnection, including the assessment of the economic impact and risk mitigation options, as well as the possibility of having multi-risks and the reduction in uncertainty by collecting larger fit-for-purpose datasets.

Assessing the probability of freedom from pine wood nematode based on 19 years of surveys

Many quarantine pests, such as the pine wood nematode (PWN, Bursaphelenchus xylophilus), are surveyed annually in all EU countries. Although a lot of resources are spent in the surveys, the confidence in pest freedom achieved with them is not commonly analysed. We assessed the probability that Finland is free from PWN, based on the surveys done in 2000–2018. We used the methods employed in the risk-based estimate of system sensitivity tool (RiBESS), which has recently been recommended for quarantine pest applications. We considered two scenarios: 1) the surveys aimed to justify phytosanitary import requirements and to facilitate exports and 2) the surveys aimed to detect invasions early to enable eradication of outbreaks. These differed only in the pest prevalence that the surveys were expected to detect. The surveys appeared to support the assumption that PWN is not present in Finland, but they did not seem extensive enough to ensure early detection of invasions. The sensitivity of the import-export surveys was greater than 0.6 in 13 years, whereas that of the early detection surveys was always below 0.25. The probability of freedom achieved in 2018 following 19 years of surveys increased asymptotically with the mean time between invasions. For the import-export surveys, this probability was at least 0.95 unless the mean time between invasions was less than 13 years. For the early detection surveys, the probability of freedom was less than 0.73 unless the mean time between invasions was 63 years or more. The results were rather robust with respect to the parameters for which exact information was lacking. To improve the assessment, a quantitative estimate of the probability of PWN invasion to Finland and a thorough assessment of the maximum area of an eradicable infestation would be needed. To gain an understanding about the true impact of quarantine pest surveys on biosecurity, more assessments, like the one presented in this paper, are needed.