Alien Invasive Pathogens and Pests Harming Trees, Forests, and Plantations: Pathways, Global Consequences and Management

Abstract

Forest health worldwide is impacted by many invasive alien pathogens and pests (IAPPs) that cause significant harm, with severe economic losses and environmental alterations. Destructive tree pathogens and pests have in the past devastated our forests, natural landscapes and cityscapes and still continue to represent a serious threat. The main driver of pathogen and pest invasions is human activities, above all global trade, which allows these invasive species to overstep their natural distribution ranges. While natural transport occurs according to a regular, expected colonization pattern (based on the dispersive capacity of the organism), human-mediated transport takes place on a larger, unpredictable scale. In order for a pathogen or pest species to become invasive in a new territory it must overcome distinct stages (barriers) that strongly affect the outcome of the invasion. Early detection is crucial to enabling successful eradication and containment. Although sophisticated diagnostic techniques are now available for disease and pest surveillance and monitoring, few control and mitigation options are usable in forestry; of these, biological control is one of the most frequently adopted. Since invasion by pathogens and pests is an economic and ecological problem of supranational relevance, governments should endorse all necessary preventive and corrective actions. To this end, establishing and harmonizing measures among countries is essential, both for preventing new introductions and for diminishing the eventual range expansion of IAPPs present at a local scale. Research is fundamental for: (i) developing effective and rapid diagnostic tools; (ii) investigating the epidemiology and ecology of IAPPs in newly introduced areas; and (iii) supporting policymakers in the implementation of quarantine regulations.

The roles of plant pathogens in old-growth forests

“…The category of invasive alien pathogens is especially threatening considered as second most important factor after habitat fragmentation/destruction affecting forests at large (Wilcove at al. 1998, Panzavolta et al 2021). The threat is deriving mostly from the pathogenic properties accounting for the lack of co-evolutive history and the lack of the evolutive history within the new environment at different spatial scales: individual tree, forest stands and forested landscapes (Parker and Gilbert 2004, Stenlid et al 2011, Stenlid and Oliva 2016, Holdenrieder et al 2004.…”

Alien phytophagous insects in forest and urban stands of Ukraine*

“…Every year, many species of insects change their ranges (Panzavolta et al 2021). Some species do not survive in a new place.…”

Filling the Gap in Southern Europe—Diversity of Cryphonectria parasitica and Associated Mycovirus (Cryphonectria hypovirus 1) in Montenegro

“…Invasive alien pathogens and pests (IAPP) pose a global threat to biodiversity, but also lead to the vast economic losses due to their impact on agriculture and forestry. Among IAPP organisms, plant pathogenic fungi play an important role, causing greater losses than non-indigenous insects, and are able to transform forest and rural landscapes in just several decades [ 1 , 2 ]. One of the unfortunate examples of such destructive power is the ascomycete fungus Cryphonectria parasitica , also called the chestnut blight fungus, listed as one of the top 100 most dangerous invasive species according to the Global Invasive Species Database [ 3 ].…”

“…in 1938 in Italy near Genoa, from where it spread, causing substantial damage [ 7 ]. The spread of invasive alien pathogens is often rapid and deleterious due to the higher host susceptibility in the new non-native range, arising from the absence of coevolution with the indigenous hosts [ 2 ]. General lack of knowledge about the distribution, host ranges, and pathogenicity of most fungal species [ 8 ], uncertain prediction of disease outbreaks, and high costs of control measures [ 1 ] make the surveillance of the spread of alien fungi of primary concern.…”