The consequences of plant pests can be very severe, for example the bacterial pathogen that already killed millions of olive trees in southern Europe. Experts Sarah Hackfort and Chiel Scholten (Technolopis Group, Germany and The Netherlands) wrote a study for the European Parliament’s Panel for the Future of Science and Technology (STOA) on “Threats from new and emerging plant pests – Options for EU management of pests’ outbreaks”. They will present their work at the STOA Panel meeting on 21 May in the European Parliament.
You have recently co-authored a study for the STOA panel on new and emerging plant pests – can you tell us about the study’s objectives and what some of these pests are?
Sarah Hackfort: In this foresight study, we are looking at the current state of plant pests, as well as what new and emerging plant pests could be relevant by 2050, and how the European Union could be better prepared with policies and instruments to meet these risks.
A plant pest is any organism that can harm plants or plant products, that reduces yields or can damage ecosystems. This includes microbes like bacteria, fungi and viruses, and also insects, mites, molluscs, and other plants.
We can distinguish plant pests as new or emerging, which is rooted in plant health governance. A new pest is one that is newly detected or recognised and is not yet regulated, while by contrast an emerging pest means that it has been recognised as a risk, it is a growing problem that may already be regulated.
An example in the EU is Xylella fastidiosa, a bacterium that has caused severe impacts in southern Europe, particularly because it affects olive trees, as well as almond trees. It is considered one of the most dangerous plant pests worldwide and has had profound effects on landscapes, economies and cultural heritage in the region, due to it being heavily shaped by olive production.
Another example is the fall armyworm (Spodoptera frugiperda), first reported in 2023 and has demonstrated how quickly pests can spread, especially under climatic shifts.
There are also other pests for which we have seen increasing outbreak notifications, like the Japanese beetle (Popillia japonica) and the oriental fruit fly (Bactrocera dorsalis), which can affect multiple crops and are strongly linked to human mediated pathways like trade and transport.
What are the factors contributing the emergence and spread of these pests?
Chiel Scholten: There are two main pathways for plant pests:
- human mediated pathways, and;
- natural pathways.
Globalisation is an important factor, with the trade of plant products but also other goods via which plant pests can enter the EU. Then there are the natural pathways, like weather driven dispersal that bring plants to different regions.
There are several trends that are influencing these pathways and are furthering the introduction and spread of plant pests in the EU. One is climate change, which can influence pest dynamics, like survival rates and host availabilities, which then influences the likelihood of pest establishment and outbreaks. It also lowers the environmental barriers that previously limited pests, which is more pronounced particularly in cooler northern regions.
International trade is generally increasing, but we have recently seen trade barriers being introduced, so we looked at different scenarios of free trade or more protectionism, and the influence this could have on plant pests.
We also looked at different agricultural land use, which influences host density. Pests can have larger effects when agricultural land is used for monocultures – which is the case when similar crops are cultivated. Land use may also affect ecological barriers to plant pests.
What are the risks posed by these pests in the EU?
Chiel Scholten: Broadly speaking, plant pests have impacts on the environment and the economy, and also potentially on food security depending on the type of crop being affected. Plant pests can lead to a loss in biodiversity and damage ecosystems, as they basically reduce the production of plant materials, which can have knock-on effects through the food chain.
Pests can incur changes in the landscape due to our efforts to control them: we often use chemical pesticides that will not just target one species and so will have wider negative effects on the environment and biodiversity.
Plant pests impose burdens on economic systems, especially when looking at the agricultural sector and the trade of crop products outside and into Europe. Worldwide, up to 40% of food crops are lost to plant pests and disease, which incurs costs of over $220 billion per year.
There are significant global impacts of plant pests, as well as at the local level, such as the impacts of Xylella fastidiosa on olive farmers, while measures to control pests can also be quite expensive for farmers.
Then there are the implications for food security – we can achieve food security partly through food imports, but if certain species around the world are affected, this can then affect food availability and prices.
What new approaches and technologies are there to respond to these risks?
Chiel Scholten: The study identified several new technologies that can help to reduce the introduction and spread of plant pests, be that for detection, surveying or management. Progress in technologies, diagnosis, artificial intelligence, remote sensing, and integrated pest management can lead to improved early detection and can support more sustainable and less intensive pest control in the future.
For detection approaches, there are various kinds of molecular and laboratory diagnostics tools, using technologies such as CRISPR-Cas or nanotechnology to create biosensors for local testing.
Sensing technologies, such as optical technologies, enable the surveying of plant health without causing damage, while imaging approaches can involve using drones or satellite images to look at the physical information of plants, fields or landscapes.
Artificial intelligence and machine learning methods can be used for automated detection, forecasting and early warnings. Data is of course essential for these approaches, so we need data mining and modelling. Nanotechnology has potential for managing pests at an early stage, with nano pesticides that can have higher effectiveness and are safer for the wider environment.
But many of these technologies are still not widely used or are still in development. They can be quite expensive to implement in the future and there is still quite some uncertainty as to the extent they may be used.
What are the positive aspects and the limitations of current responses/containment strategies in the EU? How could the EU be better prepared for new and emerging plant pests?
Sarah Hackfort: The EU has a very strong toolbox in place to deal with plant pests, there is a very clear legal framework with different legislation, the main one being the EU Plant Health Law. This Regulation is the most important instrument in plant health governance, as it sets out who does what, what pests are listed and how they are assessed, and what happens when something is detected.
The Regulation acts as a governance framework for phytosanitary standards and rules for Member States, but in practice it is often most visible when an outbreak is detected, with a strong emphasis on well-defined response mechanisms. This includes demarcated areas, movement restrictions, and containment or eradication actions. There is also coordination across Member States, with systems for sharing outbreak notifications.
Different bodies have different responsibilities for strengthening the preparedness of the EU, for example the relatively new Plant Health Emergency Team, which is designed to support Member States when outbreaks occur and rapid action is needed. Once a plant pest is detected, assessed, and regulated, specific measures can be triggered and coordinated across countries.
This kind of list-based, regulated-pest system has clear strengths: it can work very well for known risks, because responsibilities and measures are defined in advance. At the same time, it can be less well-suited to anticipating genuinely new and emerging pests – especially where risks arise through new pathways, for example, through changing trade patterns or where pests exploit new host plants or become viable under changing climatic conditions.
That is why, alongside the Regulation’s prevention and preparedness elements, such as surveillance and import controls, we also need stronger anticipation capacity for unknown or fast-evolving risks.
The main new pathways are human-mediated, particularly in trade and E-commerce, as well as tourism, and this is a problem because only a small share of goods can be realistically inspected.
One problem is that capacity to react is very uneven and there are budget and funding constraints for national plant protection organisations. So, this is important to note, that even if there is a good legislative and governance framework in place, there can be an implementation and investment gap in terms of funding, training, infrastructure and the availability of current and future technologies.
The EU needs to be more proactive, complementing the existing list-based regime with a stronger pathway- and risk-based approach that builds more expertise, anticipation capacity and resilience into the system. Our study developed several scenarios that explore the kinds of policy interventions that could be used for future responses to new and emerging plant pests, helping the EU to be better prepared for unknown or fast-evolving risks.