Richard H. Shaw

Despite increasing awareness of invasive non‐native species (INNS) and enhanced biosecurity controls in many countries, INNS are still arriving and establishing in new destinations, remaining a globally acknowledged threat to native biodiversity. Preventing the introduction of INNS, as opposed to controlling them once they have arrived, is recognised as the most effective approach to their management. Horizon scanning represents one of the key tools to identify high‐risk INNS that have yet to arrive within a region and has been applied in many contexts around the world, but to date there have been no studies that systematically assess the effectiveness of this approach. Here, we revisit the horizon scan for Great Britain conducted in 2013 that assessed the likelihood of high‐risk INNS arriving within the next 10 years, establishing and having an impact on biodiversity and ecosystems. We evaluated the success of this exercise in predicting arrival of these species within the subsequent 10 years. Ninety‐two species were shortlisted in the 2013 horizon scan. In total, 31 of the 92 species identified in the 2013 horizon scan had arrived by 2023. We found that 12 of the top 20 species had arrived within 10 years. In predicting arrival, there was a significant effect of species having arrived previously to Great Britain, and the number of countries in Western Europe and Baltic countries in which an INNS was found prior to 2013. Policy implications : We conclude that horizon scanning provides a rapid, affordable and successful mechanism to predict the arrival of high‐risk INNS. We highlight the importance of citizen science, including biological recording, and of local expertise for detecting and documenting arrival of INNS. We discuss knowledge gaps that could help inform and improve future horizon scanning. In addition, we recommend regularly repeating horizon scanning exercises to support biosecurity and awareness raising for INNS.

Invasive alien plant species (IAPs) are causing significant negative impacts on agricultural production, threatened native species and ecosystems, the services they provide and public health thereby affecting European biodiversity and its economy. IAPs invade all types of natural and managed habitat and their impacts, through increased numbers and area invaded, are growing exponentially. Current control options in Europe are largely limited to manual and chemical control, which is high cost, short‐term in effectiveness and with regards to chemical control declining in public acceptability. Globally, classical biological control (CBC) is widely and successfully used to manage many IAPs. CBC aims to redress the ecological imbalance caused by the IAPs, generally being released without their natural enemies. The steps are to select, risk assess potential specific natural enemy biocontrol agents of the IAP (from the IAP's native range) and follow regulatory approval prior to releasing them to ecologically suppress their abundance. CBC is not widely used in Europe. Only five active programmes exist. In this paper, we apply an existing framework to develop a ranked list of environmental IAPs named in the EU Regulation on Invasive Species for biocontrol. We used a scoring system based on existing knowledge on the IAPs impacts, the amount of effort needed to deliver a CBC programme targeting them and the feasibility and likelihood of success of such programmes. We identify 16 IAPs in Europe for which CBC has relatively high potential and discuss existing knowledge that can underpin any future investments in such activities against each of these IAPs. The top three species being Pontederia crassipes, Pistia startiotes and Acacia saligna. This research should support decision‐making on the instigation of future CBC programmes against environmental IAPs in Europe. We set this analysis in the context of other operational and regulatory constraints on developing CBC programmes against environmental IAPs in Europe.

The global sustainability agenda is increasing the demand for reduction in inputs into agricultural production while maintaining profitable yield of quality products. Plant diseases are a major constraint for both yield and product quality, but often tools for their control are ineffective or lacking. Biological control using antagonistic microorganisms has long been a subject of research resulting in a wide range of products that are now available and marketed in specific territories around the world. These preparations are often niche products with narrow uses. The research effort is intense both to develop new biological control agents (BCAs) and to obtain knowledge of the mechanisms underlying biological disease control. The prospects for biological control are promising. As a minimum, BCAs supplement other sustainable disease management practices such as disease resistance, and present opportunities for controlling diseases for which other approaches are ineffective or unavailable. We can realistically expect increasing use of BCAs to control crop diseases in ways that will benefit the environment. This review paper arose from a webinar held by the British Society for Plant Pathology as part of the International Year of Plant Heath (IYPH2020), at which many of the 300 participants posed or discussed interesting questions. This review is based on that input and the panel members at the webinar are all included as co‐authors in this review.

Epiplema albida (Hampson) (Lepidoptera: Uraniidae, Epipleminae) from Sri Lanka, was studied to assess its safety for use as a biological control agent for Sri Lankan privet, Ligustrum robustum subsp. walkeri (Oleaceae) in La Réunion and other Mascarene Islands. Larval no-choice feeding tests using newly hatched larvae, larval development tests, and multiple choice oviposition tests were used. Adult females of E. albida are shown to have highly selective oviposition behaviour and the species is physiologically restricted to very few hosts for feeding and development. The risk to key test plants in La Réunion is minimal, so this species can be considered for use as a biological control agent there, but would need further evaluation for potential use elsewhere.

We contend that invasion ecology requires a universal, measurable trait of species and their interactions with resources that predicts key elements of invasibility and ecological impact; here, we advocate that functional responses can help achieve this across taxonomic and trophic groups, among habitats and contexts, and can hence help unify disparate research interests in invasion ecology.

After a difficult start, classical biological control of weeds is becoming recognized as an option for management of invasive plants in European Union (EU) Member States with intentional releases in three countries over the past 5 years. Many European countries are benefitting from the presence of Stenopelmus rufinasus, the azolla weevil, which has been accidentally introduced to the region. However, the UK experience with the official release of the psyllid Aphalara itadori against Japanese knotweed (Fallopia japonica) and the subsequent release of the rust Puccinia komarovii var glanduliferae against Impatiens glandulifera showed the regulatory framework that could be followed by EU Member States. This process was followed in advance of the subsequent release of Trichilogaster acaciaelongifoliae, a specific Australian bud‐galling wasp, against the invasive Acacia longifolia in Portugal. Soon the case of Ophraella communa, another accidental introduction that is severely limiting Ambrosia artemisiifolia populations, will influence affected countries, some of which have been uninterested in this technique until now, to consider the advantages and disadvantages of classical biocontrol. The future looks bright for classical weed biocontrol and the EU Regulation on Invasive Species should further aid this situation.