Marco Pautasso

• PhD
• EFSA European Food Safety Authority

Forest pathology, the science of forest health and tree diseases, is operating in a rapidly developing environment. Most importantly, global trade and climate change are increasing the threat to forest ecosystems posed by new diseases. Various studies relevant to forest pathology in a changing world are accumulating, thus making it necessary to pro...

Models of epidemics in complex networks are improving our predictive understanding of infectious disease outbreaks. Nonetheless, applying network theory to plant pathology is still a challenge. This overview summarizes some key developments in network epidemiology that are likely to facilitate its application in the study and management of plant di...

Forest ecosystems face multiple challenges due to climate change, invasive species, urbanization, land use change and the interactions between these global change drivers. This review provides an overview of such challenges for the case study of Insubria. Insubria is a region on the Southern side of the European Alps, famous for its stunning lakes...

Pautasso M. and Parmentier I. 2007. Are the living collections of the world’s botanical gardens following species-richness patterns observed in natural ecosystems? Bot. Helv. 117: 15 – 28. Botanical gardens aim to promote the awareness, study and conservation of plant species diversity, but little is known about the species diversity of botanical...

Interdisciplinary research is becoming more frequent because many contemporary issues can only be successfully addressed by integrating different perspectives. One general feature of the various scientific fields is peer review, i.e. the assessment and improvement of submissions to journals, conferences and workshops. Whilst there exist guidelines...

In accordance with the EFSA Strategy 2027 outlining the need for fit‐for‐purpose protocols for EFSA generic scientific assessments, the EFSA Panel on Plant Health (PLH Panel) developed standard protocols to harmonise the problem formulation process and outputs for mandates addressing recurrent scientific questions. Three types of recurring EFSA pla...

The European Commission requested the EFSA Panel on Plant Health to conduct a pest categorisation of Coniella castaneicola (Ellis & Everh) Sutton, following commodity risk assessments of Acer campestre, A. palmatum, A. platanoides, A. pseudoplatanus, Quercus petraea and Q. robur plants from the UK, in which C. castaneicola was identified as a pest...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a quantitative risk assessment for the EU of African Leucinodes species (Lepidoptera: Crambidae), which are fruit and shoot borers, especially of eggplant type fruit. The assessment focused on (i) potential pathways for entry, (ii) distribution of infested im...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a quantitative risk assessment of Leucinodes orbonalis (Lepidoptera: Crambidae), the eggplant fruit and shoot borer, for the EU. The assessment focused on potential pathways for entry, climatic conditions favouring establishment, spread and impact. Options fo...

Following the commodity risk assessment of bonsai plants (Pinus parviflora grafted on Pinus thunbergii) from China performed by EFSA, the EFSA Plant Health Panel performed a pest categorisation of Pyrrhoderma noxium, a clearly defined plant pathogenic basidiomycete fungus of the order Hymenochaetales and the family Hymenochaetaceae. The pathogen is...

Following the EFSA commodity risk assessment of Malus domestica plants imported from Türkiye into the EU, the EFSA Panel on Plant Health performed a pest categorisation of Pratylenchus loosi (Nematoda: Pratylenchidae) for the EU. Pratylenchus loosi belongs to the order Rhabditida, subfamily Pratylenchidae. This nematode is not known to be present i...

Following the commodity risk assessments of bonsai plants from China consisting of Pinus parviflora grafted on P. thunbergii performed by EFSA, the EFSA Plant Health Panel performed a pest categorisation of Pestalotiopsis disseminata, a clearly defined plant pathogenic fungus of the family Pestalotiopsidaceae. The pathogen has been reported on herb...

Following an EFSA commodity risk assessment of bonsai plants (Pinus parviflora grafted on Pinus thunbergii) imported from China, the EFSA Plant Health Panel performed a pest categorisation of Pestalotiopsis microspora, a clearly defined plant pathogenic fungus of the family Pestalotiopsidaceae. The pathogen was reported on a wide range of monocotyl...

The EFSA Panel on Plant Health performed a pest categorisation of Hoplolaimus galeatus (Nematoda: Hoplolaimidae) for the EU. H. galeatus belongs to the order Rhabditida, subfamily Hoplolaiminae. This nematode is not reported from the EU and is not included in the EU Commission Implementing Regulation 2019/2072. It is widely distributed in the USA a...

The EFSA Panel on Plant Health conducted a pest categorisation of the avocado sunblotch viroid (ASBVd) for the EU. The identity of ASBVd, a member of the genus Avsunviroid (family Avsunviroidae) is clearly defined and detection and identification methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2...

Les changements globaux, combinant réchauffement climatique et invasions biologiques, menacent de plus en plus les écosystèmes forestiers. Différentes essences forestières ont été victimes de crises sanitaires ces dernières années en Europe. Les agents biotiques (champignons pathogènes, insectes ravageurs, bactéries, nématodes,…) peuvent jouer diff...

The EFSA Plant Health Panel performed a pest categorisation of Diplodia bulgarica, a clearly defined plant pathogenic fungus of the family Botryosphaeriaceae. The pathogen affects Malus domestica, M. sylvestris and Pyrus communis causing various symptoms such as canker, twig blight, gummosis, pre- and post-harvest fruit rot, dieback and tree declin...

The EFSA Plant Health Panel performed a pest categorisation of Coleosporium asterum (Dietel) Sydow & P. Sydow, Coleosporium montanum (Arthur & F. Kern) and Coleosporium solidaginis (Schwein.) Thüm, three basidiomycete fungi belonging to the family Coleosporiaceae, causing rust diseases on Pinus spp. (aecial hosts) and on Asteraceae (telial hosts)....

The EFSA Plant Health Panel performed a pest categorisation of Coleosporium eupatorii Arthur ex Cummins, a clearly defined heteroecious fungus of the family Coleosporiaceae, causing rust diseases on five-needle Pinus spp. (aecial hosts) and on several genera of the Asteraceae family (telial hosts), such as Eupatorium spp. and Stevia spp. C. eupator...

The EFSA Panel on Plant Health updated its 2017 pest categorisation of coconut cadang cadang viroid (CCCVd) for the EU territory due to new data on its host range. The identity of CCCVd, a member of the genus Cocadviroid (family Pospiviroidae), is established and detection and identification methods are available. It is included as a quarantine pes...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a quantitative pest risk assessment of Elasmopalpus lignosellus (Lepidoptera: Pyralidae), the lesser cornstalk borer, for the EU. The assessment considered entry, establishment, spread and impact. Two scenarios for establishment were considered: (i) under cur...

The EFSA Plant Health Panel performed a pest categorisation of Neoscytalidium dimidiatum, a clearly defined plant pathogenic fungus of the family Botryosphaeriaceae. The pathogen affects a wide range of woody perennial crops and ornamental plants causing symptoms such as leaf spot, shoot blight, branch dieback, canker, pre- and post-harvest fruit r...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of the citrus fruit midge Resseliella citrifrugis (Diptera: Cecidomyiidae), an oligophagous species, which feeds on fruits of Citrus spp., and is reported from China. The pest was temporarily regulated in October 2022 (Regulation (EU) 2022/1...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of Citripestis sagittiferella (Lepidoptera: Pyralidae), the citrus pulp borer, an oligophagous pest reported from South-East Asia and restricted to Citrus spp. The entry risk assessment focused on the citrus fruit pathway. Two scenarios were...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of Xanthomonas citri pv. viticola (Xcv). This pest causes bacterial canker of grapevine and is reported from Brazil and India. Two scenarios were considered: scenario A0 (current practice) and A2 (additional control measures). For the fresh...

Tree diseases are important agents of ecological disturbance in wooded ecosystems. Native tree diseases create forest gaps, thus diversifying forest structure and creating habitat for many organisms. Tree diseases are also part of biodiversity, but they have seldom been considered from a conservation biology perspective. More diverse forests are ge...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest risk assessment of Amyelois transitella (Lepidoptera: Pyralidae), the navel orangeworm, for the EU. The quantitative assessment considered two scenarios: (i) current practices and (ii) a requirement for chilled transport. The assessment focused on path...

Pest risk assessments are required to take phytosanitary measures to protect plant health. In the European Union, the Scientific Panel on Plant Health (PLH) of the European Food Safety Authority was established in 2006 as the reference body for risk assessment in the plant health area. Risk assessments address four steps: introduction, establishmen...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of four phytoplasmas of tuber-forming Solanum spp. known to occur only outside the EU or having a limited presence in the EU. The only tuber-forming species of Solanum reported to be phytoplasma infected is S. tuberosum. This opinion cov...

Following a request from the European Commission, the EFSA Panel on Plant Health prepared a list of non-EU phytoplasmas of tuber-forming Solanum spp. A systematic literature review and search of databases identified 12 phytoplasmas infecting S. tuberosum. These phytoplasmas were assigned to three categories. The first group (a) consists of seven no...

Forstschutz und Extremereignisse (Essay) Das Zusammenspiel von höheren Temperaturen, häufigeren Extremereignissen und internationalem Austausch von Holz und Pflanzenmaterial ist eine neue Herausforderung für die Nachhaltigkeit unserer Wälder. Der vorliegende Beitrag liefert einige Diskussionspunkte zum Thema aus der Sicht des Forstschutzes. Biologi...

Abstract Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of nine phytoplasmas of Cydonia Mill., Fragaria L., Malus Mill., Prunus L., Pyrus L., Ribes L., Rubus L. and Vitis L. (hereafter “host plants”) known to occur only outside the EU or having a limited presence in the EU. This opin...

Abstract Following a request from the European Commission, the EFSA Panel on Plant Health prepared a list of non‐EU phytoplasmas of Cydonia Mill., Fragaria L., Malus Mill., Prunus L., Pyrus L., Ribes L., Rubus L. and Vitis L. A systematic literature review and search of databases identified 27 phytoplasmas infecting one or more of the host genera u...

Writing a narrative literature review requires careful planning. This chapter summarizes some key steps in reviewing the literature. First, a team needs to be formed. Second, a topic needs to be chosen. This needs to be relevant to the author's research/teaching interests and a well‐defined issue. Third, a thorough search strategy using a variety o...

Abstract Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of the entry of Pantoea stewartii subsp. stewartii on maize seed imported by the EU from the USA. This pest is a Gram‐negative bacterium which causes Stewart's vascular wilt and leaf blight of maize (including sweet corn), a disease...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Clavibacter sepedonicus, a well-defined and distinguishable bacterial plant pathogen of the family Microbacteriaceae. C. sepedonicus causes bacterial ring rot of potato and is reported from North America, Asia and Europe. The bacteriu...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of the Ralstonia solanacearum species complex (RSSC), a distinguishable cosmopolitan group of bacterial plant pathogens (including R. solanacearum, Ralstonia pseudosolanacearum and two subspecies of Ralstonia syzygii) of the family Burkh...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Gymnosporangium spp. (non-EU), a well-defined and distinguishable group of fungal plant pathogens of the family Pucciniaceae affecting woody species. Many different Gymnosporangium species are recognised, of which at least 14 species...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Cronartium spp. (non-EU), a well-defined and distinguishable group of fungal pathogens of the family Cronartiaceae. There are at least 40 species described within the Cronartium genus, of which two are considered native to the EU (C....

Following a series of requests for scientific advice from the European Commission starting in 2013, the European Food Safety Authority (EFSA) conducted a pest risk assessment and created a comprehensive Xylella fastidiosa host plant database. The last update of the database, published in September 2018, includes information on host plants of both X...

Abstract Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Melampsora farlowii, a well‐defined and distinguishable fungus of the family Melampsoraceae. M. farlowii is the causal agent of a leaf and twig rust of hemlocks (Tsuga spp.) in eastern North America. The pathogen is regulated...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Cronartium harknessii, Cronartium kurilense and Cronartium sahoanum, which are well-defined and distinguishable tree fungal pathogens of the family Cronartiaceae. In 2018, these species were moved from the genus Endocronartium to the...

Abstract This Guidance describes a two‐phase approach for a fit‐for‐purpose method for the assessment of plant pest risk in the territory of the EU. Phase one consists of pest categorisation to determine whether the pest has the characteristics of a quarantine pest or those of a regulated non‐quarantine pest for the area of the EU. Phase two consis...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Chrysomyxa arctostaphyli, a well-defined and distinguishable fungal species of the family Coleosporiaceae. The pathogen is regulated in Council Directive 2000/29/EC (Annex IAI) as a harmful organism whose introduction into the EU is b...

Following a request from the European Commission, the EFSA Plant Health Panel performed a pest categorisation of Pantoea stewartii subsp. stewartii (hereafter P. s. subsp. stewartii). P. s. subsp. stewartii is a Gram-negative bacterium that causes Stewart's vascular wilt and leaf blight of sweet corn and maize, a disease responsible for serious cro...

Following a request from the European Commission, the EFSA Plant Health Panel performed a pest categorisation of Melampsora medusae, a well-defined and distinguishable fungal species of the family Melampsoraceae. The pathogen is regulated in Annex IAI of Council Directive 2000/29/EC as a harmful organism whose introduction into the EU is banned. M....

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Arceuthobium spp. (non-EU), a well-defined and distinguishable group of parasitic plant species of the family Viscaceae, also known as dwarf mistletoes. These are flowering plants parasitising a wide range of conifers of the families...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Guignardia laricina, a well-defined and distinguishable fungal species of the family Phyllostictaceae. The pathogen is regulated in Council Directive 2000/29/EC (Annex IAI) as a harmful organism whose introduction into the EU is banne...

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Coniferiporia sulphurascens and Coniferiporia weirii, two well-defined and distinguishable fungal species of the family Hymenochaetaceae. The pathogens are regulated in Council Directive 2000/29/EC (Annex IAI, under the previous name...

Following a request from the European Commission, the EFSA Plant Health Panel performed a pest categorisation of Sphaerulina musiva, a well-defined and distinguishable fungal species of the family Mycosphaerellaceae. Following a recent phylogenetic analysis of the genus Septoria and other closely related genera, a new name (S. musiva) was introduce...

Following a request from the European Commission, the EFSA Panel on Plant Health (PLH) performed a pest categorisation of Mycodiella laricis-leptolepidis, a well-defined and distinguishable fungal species of the family Mycosphaerellaceae. The former species name Mycosphaerella laricis-leptolepis is used in the Council Directive 2000/29/EC. The path...

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a pest categorisation of Bretziella fagacearum, a well-defined and distinguishable fungal species of the family Ceratocystidaceae. The species was moved from the genus Ceratocystis to a new genus Bretziella following phylogenetic analysis of the species an...

Abstract Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a pest categorisation of Anisogramma anomala, a well‐defined and distinguishable fungal species of the family Valsaceae. The pathogen is regulated in Annex IIAI of Council Directive 2000/29/EC as a harmful organism whose introduction into the EU i...

Abstract Following a request from the European Commission, the EFSA Panel on Plant Health (PLH) performed a pest categorisation of Davidsoniella virescens, a well‐defined and distinguishable fungal species of the family Ceratocystidaceae. The species was moved from the genus Ceratocystis to the genus Davidsoniella following a revision of the family...

Abstract Following a request from the European Commission, the EFSA Panel on Plant Health (PLH) performed a pest categorisation of Stegophora ulmea, a well‐defined and distinguishable fungal species of the family Sydowiellaceae. S. ulmea causes a tree disease known as black spot of elm (Ulmus spp.). The pathogen is reported from North America (nati...

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a pest categorisation of Pseudocercospora pini-densiflorae, a well-defined and distinguishable fungal species of the family Mycosphaerellaceae. The regulated harmful organism is the anamorph Cercoseptoria pini-densiflorae (synonym Cercospora pini-densiflor...

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 diff...

Open-space labs and research environments are increasingly common worldwide. They are supposed to facilitate interactions among researchers, but can be disruptive to those who need to be in a quiet environment in order to concentrate. This problem is increasingly felt across the natural, medical and social sciences, has a clear interdisciplinary an...

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a risk assessment for Atropellis spp. in the EU focusing on the risk of entry, the host range and the potential impacts. Atropellis is a fungal pathogen of several Pinus spp. in North America. The pathogen has not been reported from Europe and is a quarant...

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a pest categorisation of Entoleuca mammata, a well-defined and distinguishable fungus of the family Xylariaceae native to North America. The species was moved from the genus Hypoxylon to the genus Entoleuca following a revision of the genus. The former spe...

Acute Oak Decline (AOD) is a new condition affecting both species of native oak, Quercus robur and Quercus petraea, in Great Britain. The decline is characterised by a distinctive set of externally visible stem symptoms; bark cracks that “weep” dark exudate are found above necrotic lesions in the inner bark. Emergence holes of the buprestid beetle,...

Microbial ecology provides insights into the ecological and evolutionary dynamics of microbial communities underpinning every ecosystem on Earth. Microbial communities can now be investigated in unprecedented detail, although there is still a wealth of open questions to be tackled. Here we identify 50 research questions of fundamental importance to...

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a risk assessment for Ceratocystis platani in the EU with the aim to assess the effectiveness of risk reduction options (RROs) on the basis of the mechanisms of spread identified in the pest categorisation (natural and human-assisted means, including water...

Following a request from the European Commission, the EFSA Plant Health (PLH) Panel performed a risk assessment for Cryphonectria parasitica in the EU with the aim to assess the current EU phytosanitary requirements and identify the risk reduction options (RROs), which would preserve the protected zone (PZ) status in some parts of the EU, where the...

Alien plant pests are introduced into new areas at unprecedented rates through global trade, transport, tourism and travel, threatening biodiversity and agriculture. Increasingly, the movement and introduction of pests is analysed with pathway models to provide risk managers with quantitative estimates of introduction risks and effectiveness of man...

Alien plant pests are introduced into new areas at unprecedented rates through global trade, transport, tourism and travel, threatening biodiversity and agriculture. Increasingly, the movement and introduction of pests is analysed with pathway models to provide risk managers with quantitative estimates of introduction risks and effectiveness of man...

This paper summarizes the first assessment by the European Food Safety Authority ( EFSA) P lant H ealth ( PLH ) P anel of a biological control agent ( BCA ) of an invasive plant. This followed a request by the European Union ( EU) C ommission to assess the risk to plant health in the EU of an intentional release of the bud‐galling wasp T richilogas...

Obligatory plant parasitic micromycetes (Chromista,Fungi) are fungi that subsist and grow on living plant tissues. These fungi comprise a considerable portion of global biodiversity and fulfill important ecological functions. Many species and their host spectra are known only insufficiently. Botanic gardens are particularly well suited for studying...

Organic farming adoption is on the rise in many countries, due to the increased awareness of farmers, citizens, governments and other stakeholders of its more sustainable nature. Various studies have investigated the socio-economic drivers (e.g., consumer demand, support measures, agricultural policies) of organic farming adoption, but less attenti...

The history of agriculture includes many animal and plant disease events that have had major consequences for the sector, as well as for humans. At the same time, human activities beyond agriculture have often driven the emergence of diseases. The more that humans expand the footprint of the global population, encroach into natural habitats, alter...

The future existence of common ash (Fraxinus excelsior), an important tree species throughout temperate Europe, is threatened. An invasive fungal disease (ash dieback) has spread through much of the distribution area of common ash. The causal agent of the disease is Hymenoscyphus fraxineus, a necrotrophic ascomycete, most probably introduced from A...

Maintaining forest health is a worldwide challenge due to emerging tree diseases, shifts in climate conditions and other global change stressors. Research on forest health is thus accumulating rapidly, but there has been little use of scientometric approaches in forest pathology and dendrology. Scientometrics is the quantitative study of trends in...

Emerging plant pests and diseases are a threat to biodiversity, food security and sustainability. In Europe, recent plant health emergencies include European ash dieback (due to the ascomycete Hymenoscyphus fraxineus), the outbreak of the bacterium Xylella fastidiosa on olive trees in Apulia, Italy and the invasion by the vinegar cherry fly Drosoph...

This brilliant and original book by Jan Zadoks, a renowned, prolific and polyglot Dutch plant epidemiologist [2], provides a systematic, learned and well-structured overview of our understanding of medieval crop protection in Europe.

The importance of seed provisioning in food security and nutrition, agricultural development and rural livelihoods, and agrobiodiversity and germplasm conservation is well accepted by policy makers, practitioners and researchers. The role of farmer seed networks is less well understood and yet is central to debates on current issues ranging from se...

Scientometric and bibliometric methods are increasingly applied to study temporal trends in scientific outputs, but there has been little application in plant and forest health. This research note uses the Google Books N-Grams search engine to explore temporal trends in the use of terms related to forest pathology in published books. The search was...

Media monitoring for emerging risks has become an essential tool in public health. This approach also has the potential to deliver early warning of emerging risks to plant health. The European Food Safety Authority (EFSA) has launched a project in collaboration with the Joint Research Centre (JRC) of the European Commission to make use of the Medic...

Current science evaluation still relies on citation performance, despite criticisms of purely bibliometric research assessments. Biological taxonomy suffers from a drain of knowledge and manpower, with poor citation performance commonly held as one reason for this impediment. But is there really such a citation impediment in taxonomy? We compared t...

Increasing the representation of women in academia is a priority challenge in higher education policy. This study uses data from the Italian University habilitation competition in 2012 to test whether this national, standardized and quantitative assessment of researchers contributed to improving the situation. The proportion of female applications...

To promote and maintain health in agricultural and food systems, appropriate criteria are needed for the description and assessment of the health of soils, plants, animals, humans and ecosystems. Here we identify the concept of resilience as a universally applicable and fundamentally important criterion of health in all relevant areas of agricultur...

Background and Aims. The botanic gardens of the world are now unmatchedex situ collections of plant biodiversity. They mirror two biogeographical patterns ( positive diversity–area and diversity–age relationships) but differ from nature with a positive latitudinal gradient in their richness. Whether these relationships can be explained by socio-eco...

A network is a natural structure with which to describe many aspects of a plant pathosystem. The article seeks to set out in a nonmathematical way some of the network concepts that promise to be useful in managing plant disease. The field has been stimulated by developments designed to help understand and manage animal and human disease, and by tec...

Meta-analysis has been recognised as a powerful method to synthetize existing published data from different studies through a formal statistical analysis. Several statistical models have been proposed to evaluate the effectiveness of treatments against plant diseases using meta-analysis, but the sensitivity of the estimated treatment effects to the...

Borrett et al. (2014) report a jump in network ecology publications between 1990 and 1991 but fail to find a cause for it. This jump in publication output is not a mystery, but a Web of Science artefact, due to the restriction of this database search to titles until 1990, whilst also abstracts and keywords are systematically searched in Web of Scie...

Crop diversity is essential for sustainable development because diverse crops cope better with disease and climate change. A way to maintain crop diversity is to sustain seed exchange among farmers. Network simulations help in establishing which network properties promote crop diversity conservation. Here, we modelled the likelihood that an introdu...