Moving to peat-free growing media is essential to allow peat bogs to recover from past exploitation. Peat has been a mainstay of horticulture for many decades and the move away from it will lead to other plant-based products being incorporated into growing media in the future. This may provide the conditions for the proliferation of pests such as sciarid flies, which often occur in decaying plant matter. There are approximately 600 species of sciarid fly in Europe and a total of c.1700 described species globally but the lifecycles of most of these species are currently unknown. In addition, there is conflicting evidence on whether sciarid fly cause physical damage to plants or whether they are just a nuisance. Understanding the extent of damage is very important. By conducting interviews with key stakeholders in the horticulture industry, this project will provide a better understanding of:

1. The specific conditions and contexts where sciarid flies could be a problem in Scotland;
2. Whether sciarid fly infestations are more prevalent in peat-free growing media;
3. The species present and their lifecycles;
4. Management options for sciarid fly.

Upcoming major changes to agricultural policies in Scotland could have significant impacts on crop health (and by extension, crop yields). There is an urgent need, before the agricultural policy reforms are finalised, to review options and identify those that maximise plant health benefits, and those where risks to plant health might be enhanced, in order to consider any mitigations or best practice recommendations that could be put in place.

This project will: (i) Review the evidence (including the scientific and grey literature and existing data) to identify the plant health impacts of the proposed measures within agricultural reform, with reference to Scotland’s key crops and the likely uptake of measures; (ii) Identify potential regulatory options (statutory, basic or enhanced) that could pose an emerging risk for plant health and biosecurity in the context of likely uptake of measures; (iii) Hold a stakeholder workshop to co-design best practices guidance to mitigate plant health risk whilst delivering biodiversity, climate and wider environmental goals and (iv) raise awareness of plant health risks associated with the proposed measures and disseminate best practice guidance to mitigate risk.

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The plant related biosecurity risks posed by bulk aggregates (e.g., sand, stone, decorative wood chips, and soil) to Scotland is currently unclear. It is theoretically possible for plant pests and pathogens to travel within such products but the evidence for this is patchy. The UK Plant Health Risk Register does not mention a specific pathway in relation to bulk aggregates which suggests that these materials are not routinely considered during pest risk analyses (beyond soil/growing media).

This scoping exercise will provide clarity on the biosecurity risks posed by bulk aggregates by a) engaging with the sector to understand where materials originate from, b) quantify how much bulk aggregate material is coming into GB, and c) investigate international approaches to managing the plant health risks regarding bulk aggregates.

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A best practice waste management guidance document was produced during PHC2021/02 (Identifying the plant health risks associated with plant waste disposal and peat-free growing media and developing best practice guidance for waste disposal and composting across sectors) to help organisations and businesses manage their plant waste effectively and reduce both the individual business risks, and the wider risks to Scotland’s plant health. However, Project PHC2021/02 identified that there were significant barriers to the uptake of better waste management practices, so an additional programme of knowledge exchange was funded by the Plant Health Centre with the aim of:

1. Sharing the best practice for waste management with those managing waste in plant nurseries, gardens, parks and other plant handling businesses.
2. Ensuring the best practice guidance is available for those applying to become Plant Healthy certified.
3. Producing a peer-reviewed publication on plant waste management to ensure the broadest reach with plant health experts.

This project addresses concerns that stakeholders, many of which will be registered as professional operators and issuing plant passports, are lacking confidence in their notifiable pest risk knowledge. For example, some people can find the UK Plant Health Risk Register (PHRR) an intimidating resource that cannot be easily searched by plant host species. The project will help address this issue by providing professional operators with the critical information on high-risk notifiable pests, in an easily accessible format, in order to support professional operators, meet their regulatory responsibilities.

PHC2022/08 will create summary overview documents that cross references the 39 notifiable pests (from the PHRR) with management measures and the requirements of the Plant Health Management Standard. Therefore, plant pest information will be presented in manner to support businesses and organisations conduct a Site and Operations Pest Risk Analysis.

PHC2022/08 is 50% match-funded from Defra

Previous PHC projects found that biocontrol is one of the elements of Integrated Pest Management (IPM) with a role to play in mitigating pesticide withdrawals. However, it is currently unclear how practical biocontrol is as a suitable alternative to pesticides in Scotland, what the opportunities are for deployment across different sectors and what barriers exist to uptake (include regulatory).

Research on biocontrol agents is required to understand a) what relevant previous work has taken place, b) the potential benefits for agricultural, horticultural and forestry applications in Scotland, and c) is the current risk assessment framework and regulatory system fit for purpose?

This project will improve our understanding of the potential of biocontrol agents in Scottish production systems and gardens; synthesising findings from workshops with stakeholders and literature review.

The Plant Health Centre was commissioned by the Scottish Government to review evidence relating to the potential of new gene editing technologies to address plant health issues in Scotland, with potential benefits, barriers to deployment and dis-benefits noted

Originally raised as a plant health issue of potential concern, the health of Alder trees in Scotland was initially investigated in project PHC2019/09: Health status of Alder in Scotland. This preliminary study found that there could be a legitimate concern over Alder that may have complex causes (several biotic and abiotic stresses were noted), and the timeline of these health issues (gradual or rapid) was unclear. Further scoping and examination of the problem by established experts was recommended, leading to this project. The project will conduct:
• Expert visitation of sites to seek evidence of problems with alder health, gain some understanding as to possible causes, and identify key dimensions of a thorough study should this prove warranted. Lab work to confirm field diagnoses.
• Preliminary citizen science request inviting site-specific records of concern over alder health (potentially via the trained Observatree volunteer network to gather data), with analysis to identify any geographic clustering.
• Produce recommendations for further work including; refined survey methodologies for widespread application by interested organisations; identification of potential candidate sites for detailed study over time, and; a discussion document on risks to existing alder of expansion of riparian woodland.

Plant health risks associated with poor composting practice or imported carrier products as peat alternatives are not well understood. Best practice guidance to minimise the plant health risks to Scotland from these activities is needed.

This work will examine and define the extent to which current UK and Scottish regulations and voluntary schemes control the way growing medium constituents must be treated prior to their inclusion in growing media, to generate an understanding around mitigating risks of spread of plant pathogens. Workshops with stakeholders will improve understanding of current practices and perceptions of alternative ‘best practice’ options for nurseries managing waste materials and for biosecurity risks of using reduced peat and peat-free growing media. A concurrent diagnostic study will identify Phytophthora species present in waste heaps from nurseries located in Scotland and the potential for these pathogens to spread into healthy plant stock either aerially or via water run-off and soil transfer.

Findings will be combined with a comprehensive desk-based study and feed into follow-up workshops on the development and introduction of ‘best practice’ guidance on the most appropriate and safest ways to manage waste growing media and plant material, to be built into the Plant Health Management Standard.

Outwith the plant-based trade sectors there are aspects of biosecurity practice for which advice remains unclear or there are no commonly agreed best practices. Two broad situations needing further evidence are 1) sites which are visited by many people, and 2) moving machinery and equipment between sites. The project will address three aspects of biosecurity where evidence is lacking:

• How can important plant species in botanic collections and historic gardens be protected from inadvertent disease introduction on the footwear, etc. of visitors?
• What is the risk of further inadvertent spread from gardens into the natural environment?
• How can gardens, nurseries, farms and the natural environment be protected from pest and disease spread through the movement of large machinery (e.g., tree harvesting machines)?

Through a desk based study that incudes literature review, contact with plant health authorities, semi-structured interviews with landowners and expert practitioners from other sectors, the project will; determine what official biosecurity advice already exists and procedures are in place in Scotland; explore other sectors which provide additional novel approaches to biosecurity; and carry out a thorough assessment of what procedures are in place, or being considered and developed, in different countries/regions to address these specific biosecurity risks.