Horticulture

Scotland is renowned for the quality of its private and public horticultural collections, and its rich cultural history of plant collecting, allotments and gardening. Horticultural plantings are of significant economic value, as well as providing amenity, health and well-being, cultural and conservation resources. However, pest and pathogens represent a major threat to this highly diverse set of plantings.

Horticultural plantings provide amenity value in public spaces, form structural components of landscaping projects, represent a significant component of urban biodiversity and are central to private, public and heritage gardens. Given the diversity of plants involved in horticulture, there is a corresponding diversity of pests and pathogens of concern, and a particular challenge is the extensive network of plant movement at a range of scales from industrial supply to movement of individual plants between gardens. This results in a highly distributed network of pest and disease vectors. The role of the public is of particular importance for horticulture, in terms of both the ownership of plants in private gardens, and as being a major source of plant movement.

 

 

Projects

Project Lead: Sarah Wynn
Insecticides are commonly used in Scottish agricultural, horticultural, forestry production, and for amenity and natural environment management purposes. Over the last 10 years, approximately 50% of UK insecticide active substances have been withdrawn due to increasing concern over human health and environmental impacts. Some of these losses will be mitigated by using alternatives but their practicality and cost under Scottish conditions is unknown. Given the likelihood that regulatory restrictions on pesticide usage will not be reduced, widespread adoption of IPM might offer a way to reduce reliance upon at risk pesticides.

This project will deliver an expert review of available literature to identify the insecticides of concern to Scotland and their association with current practices. This targeted review will identify available alternatives and their efficacy, and any interdependencies and evidence gaps will be identified. A key outcome of this call will be case studies of the alternative methods adopted by stakeholders to mitigate the impact of insecticide withdrawal, combined with desk-based and expert opinion and analysis on their efficacy, practicality and cost.
Project Lead: Matt Elliot
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
Project Lead: Mariella Marzano
Three projects (PHC2019/04/05/06) were conducted in 2020/21 that investigated large-scale biosecurity risks to Scotland from several supply-chains and planting approaches. This project was commissioned, within the original scope of the aforementioned projects, to conduct further research with a strong likelihood of strengthening and expanding their findings. This project seeks to engage with hard-to-reach actors and the wider sector through their membership organisations.

PHC2021/02 will implement an Action Research approach, delivered through workshops co-designed with network organisations, to better understand current plant biosecurity risks in several sectors, to identify their plant health knowledge needs, and to begin to embed biosecurity training within existing organisations, programmes and processes.

The outcomes of the project will be:
• An enhanced understanding of the knowledge and training needs of different sectors and the identification of biosecurity actions that will fill some of the gaps identified by PHC2019/04/05/06
• The identification of further training needs and potential approaches to address the problems identified
• A legacy of close working relationships between the PHC and several network organisations, key to future plant biosecurity research or training delivery activities
Project Lead: Stephen Hendry
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.
Project Lead: Chris Pollard
Whilst it is generally agreed that ‘prevention is better than cure’ in plant health, translating such logic into precautionary actions does not always happen. Precautions can be encouraged in a variety of ways – through development of implementable actions, risk assessments, encouragement of best practice, and general appeals to adopt approaches which prevent future losses. However, this does not adequately address risky behaviour. Whilst better information may not be sufficient to change practices, there is a weakness in our ability to justify precaution. This project seeks to address this gap by considering whether there are different approaches, or additional information which might be considered.

Drawing upon and summarise existing literature, in addition to engagement with experts and practitioners with knowledge of existing sectoral practices in Scotland, UK and internationally, as well as gap analysis, the project will generate a better understanding of the rationale for taking precautions and an improved evidence base with which to justify taking action, answering four main questions:
• What are the current barriers to adopting precautionary measures?
• How can barriers be reduced?
• What are the limitations of the current risk assessment process?, and
• What are the priority areas for action and further research?
Project Lead: Matt Elliot
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.
Project Lead: Rehema White
We have commissioned a project to review and further develop the PHC’s Communications Strategy to help develop further networks and collaborations, while building on existing relationships to improve knowledge flows in relation to plant health across Scotland. This project will draw on and align with previous and ongoing PHC research projects and will address:

1. What is the overall goal and vision for PHC and how do we articulate this for different groups and sectors?
2. What do we want to communicate, when and to whom?
3. How do we want to communicate to different audiences and for these different purposes?
4. How do we optimise budget and human resource in communicating about plant health?

Impact: The outcome of this project will be a Communication Strategy outlining the goal of communication, roles and responsibilities and a process, including an annual cycle of reflection to permit update or modification on a regular basis and linking to the communication matrix.
Project Lead: Peter Skelsey
Potato Cyst Nematode (PCN) is a threat to the Scottish seed potato and bulb industries: SASA estimates that over 13% of the area regularly planted with potatoes in Scotland is now infested with PCN, with an estimated increase in spread of 5% per year. Recently, following a working group on PCN, a report entitled ‘Potato cyst nematode (PCN) and the future of potato production in Scotland’ was submitted to Scottish Government highlighting the PCN problem in detail and outlining practical recommendations for its reduction. However, in order to maximise and target resources for such a reduction, a better understand is needed of i) the main areas of infestation in Scotland and how this is changing over time, ii) what key factors are responsible for that spread (be it geographic, climatic, agronomic etc) and iii) which management options would allow us to make the biggest impact on reducing spread.

Impact: The outcomes of this project to provide guidance to both policy and industry on the most effective ways to reduce spread of PCN.
Project Lead: Ashleigh Holmes
To maximise the impact of the work of the Centre, we need to be effective at the production, exchange and implementation of plant health knowledge across the four plant sectors, forestry, horticulture, environment and agriculture. To this end we have had a Stakeholder Engagement Strategy developed (PHC2020/02). This project, that runs for a 12-month duration, will implement this strategy. The aims of the project are to conduct further research on plant health knowledge flows, develop the Centre’s relationship with plant health stakeholders, foster a more dominant social media narrative for the Centre and lead the translation and distribution of knowledge to plant health practitioners, liaising closely with SEFARI Gateway.

Impact: Keep plant health and biosecurity at the forefront of our stakeholders’ minds, and a high priority for them, raising stakeholder awareness about the risks from plant pests and pathogens and the solutions available for their management and control, and raising the profile of the Plant Health Centre and our online resources.
Project Lead: Daniel Chapman
Xylella fastidiosa is a bacterial plant pathogen that can cause disease in a broad range of hosts. There are currently major Xylella outbreaks in Southern France, including Corsica, Italy, mainland Spain and the Balearic Islands. Although Xylella has so far not been detected in Scotland (or UK), an outbreak would have serious impacts on any host plant-related activities/businesses and the wider environment. To understand the risk posed to Scotland’s plants from Xylella, and to be adequately prepared if it is detected, there are important knowledge gaps that must be addressed. This project will build on the results of the previous PHC Xylella projects (PHC2018 / 04 /05 / 06) to further refine Scottish Government’s contingency and preparedness measures for the possible arrival of Xylella fastidiosa.

Impact: Deliver recommendations as to the suitability of vector trapping methods and eradication strategies, if deployed in Scotland.

Publications

Forestry, Horticulture, Agriculture, Environment | Final Report and Policy Document

Improving knowledge of Xylella fastidiosa vector ecology: modelling vector occurrence and abundance in the wider landscape in Scotland

May 2022

If introduced to the UK, the insect-vectored, bacterial plant pathogen Xylella fastidiosa could be a serious threat to trees and other plants. There is a lack of knowledge about the ecology and distributions of Xylella vectors in Scotland and the potential effects of this on any outbreak of the disease, which this project aimed to address.

Assessment of large-scale biosecurity risks to Scotland

December 2021

PHC commissioned an assessment of large-scale biosecurity risks with a focus on three areas of concern:

  1. non-specialist and online horticulture sales;
  2. landscaping and infrastructure;
  3. planting for environmental benefits.

An additional area was the potential for modelling to support decision making across these areas of concern.  This policy report summaries each report and highlights the key findings and suggested actions.  

Assessment of large-scale plant biosecurity risks to Scotland from non-specialist and online horticultural sales

October 2021

This project focused on an initial exploration of tree and plant biosecurity risks to Scotland arising from large-scale movement of plants via non-specialist (those for which plants are not their primary product type, e.g., supermarkets, DIY and lifestyle stores) and online plant retailers. By better understanding the characteristics of these retailer types, the plant health behaviours they undertake, and the challenges they face, potential avenues were offered for greater engagement and collaboration on biosecurity with this important, but understudied and hard to reach sector.

Assessment of plant biosecurity risks to Scotland from large scale plantings for landscaping and infra-structure projects

October 2021

Planting for large-scale landscaping and infrastructure can typically involve tens of thousands of individual plants, potentially threatening plant health in Scotland due to the biosecurity risks of imports and widespread planting of infested or diseased plants. This project aimed to understand the extent and means to mitigate against such plant biosecurity risks with a focus on mapping the pathways from plant specification through to planting and establishment and highlight different biosecurity awareness for actors, in decision-making and procurement processes.

Assessment of plant biosecurity risks to Scotland from large scale tree plantings for environmental benefits

October 2021

This report features five case studies from across Scotland and examines risks associated with large scale tree planting schemes, levels of awareness around pests and diseases, and how the decisions and actions of those involved can serve to reduce or exacerbate pest and disease related threats and long-term tree health. Each case study was unique in respect to their combination of location, site conditions, ownership, management objectives, species choice, supply chains and management activities. By highlighting best practice and lessons learned, it was hoped to ensure that future planting schemes can be successful and, importantly, reduce the likelihood of pests and diseases being introduced and spread into the wider environment.

The potential of ecological and epidemiological models to inform assessment and mitigation of biosecurity risks arising from large scale planting

October 2021

Large scale planting projects linked to infra-structure such as transport networks and major housing projects or to planting for environmental benefits (e.g. urban greening, woodland restoration) pose high biosecurity risks due to the high number and types of plants involved. This report focusses on whether and how ecological and epidemiological model frameworks can inform assessment and mitigation of biosecurity risks from large scale planting using a combination of literature review and stakeholder engagement. 

Forestry, Horticulture, Environment | Final Report and Policy Document

Metabarcoding analysis of Phytophthora diversity in spore traps and implications for disease forecasting in the P. ramorum management zone

May 2021

Surveillance and monitoring of airborne pathogens is a key tool in the management of healthy forests and controlling disease outbreaks. A Scottish Forestry-funded project was carried out in autumn 2019 to validate different spore-trapping techniques for monitoring airborne P. ramorum inoculum using a species-specific qPCR assay. This project aimed to add further value to the Scottish Forestry project by investigating the suitability of DNA metabarcoding for screening spore trap samples for P. ramorum and other Phytophthora species, seeking early data for aerially dispersed Phytophthora species that may become problematic in UK forests. The study highlighted the value of both monitoring P. ramorum dispersal and detecting other Phytophthora species, to predict and understand changes in disease severity in UK tree host species. Recommendations included that the use of both rain and wind-borne inoculum capture methods might be advantageous due to the variety of weather conditions under which inoculum can disperse.  Lineage testing in Southwest Scotland should be carried out to look at the prevalence of lineage EU1 in the EU2 area and to monitor for presence of North American lineages. Development of a new DNA barcode more specific to Phytophthora would be beneficial.

Horticulture, Agriculture | Final Report and Policy Document

Monitoring for BMSB in Scotland - Final Report and Policy Summary

March 2021

The increase in global trade brings with it the risk of spread of new pests and diseases into Scotland. Halyomorpha halys, Brown Marmorated Stinkbug (BMSB) is an invasive pest that has already become established in North America and several European countries. The insect aggregates inside houses over winter and can cause problems as an urban nuisance pest in homes as well as being a pest of agriculture. In this project, co-ordinated monitoring for the presence of BMSB was undertaken by teams at SASA and the James Hutton Institute. A reference collection of voucher specimens of common UK stinkbug species was established, including DNA barcoding. A process-oriented climate-based niche model was used by a team at SRUC to determine the areas in Scotland that are suitable for the establishment of BMSB under current and future climates.

Recommendations and suggested 'next steps', including encouraging further surveillance, are detailed in the report and policy summary documents.

Forestry, Horticulture, Agriculture, Environment | Final Report and Policy Document

PHC2020/09: Economic Impact of Pesticide Withdrawals to Scotland, with Case Studies

March 2021

Chemical forms of plant protection are widely used in Scottish agricultural, horticultural and forestry production plus for amenity and natural environment management purposes.  The availability and use of active substances in pesticides are closely regulated and increasing concern over human health and environmental impacts has led to a greater likelihood that some existing approvals will be withdrawn and/or that approvals for new products will not be granted.  Potential impacts from withdrawal of these pesticides are of policy interest and this summary report builds on the data and results from project PHC2018/15 (Potential impacts arising from pesticide withdrawals to Scotland’s plant health) and uses case studies to understand the likely magnitude and distribution of potential impacts and how they may be mitigated. 

PHC2018/15: Potential Impacts Arising from Pesticide Withdrawals to Scotland’s Plant Health

November 2020

The use of pesticides to manage plant pests and diseases is a key management intervention across plant health sectors, particularly in agriculture, horticulture and commercial forestry production. Pesticide withdrawals through legislation, coupled with resistance development and their impact on plant health, have emerged as key concerns for Scottish plant health stakeholders.  This project quantifies the impacts on Scottish plant health that will arise from pesticide withdrawal scenarios and sets this in the context and time frame of alternative management tools. 

Impact of climate change on the spread of pests and diseases in Scotland

June 2020

This project constructed a modelling framework which combined epidemiological and economic modelling.  The modelling framework was used to study predictions of spread and economic impact of pests which are not currently in the UK, including Xylella fastidiosa, Candidatus Liberibacter solanacearum (Zebra chip) and Ips typographus (Eight toothed Spruce Bark Beetle). 

Impact:  A web/desktop application is available to the PHC and Scottish Government to analyse the effects of climate change on the spread and economic impact of new threats. 

Expansion of PHC Online Plant Health Resources

May 2020

This project has expanded the PHC online Resource Bank for plant health threats to the Natural Environment sector in Scotland to include information sources for the remaining three sectors (Forestry, Agriculture and Horticulture). Information sources for Forestry, Agriculture and Horticulture were compiled and evaluated, and a Knowledge Bank relevant to each sector is now online at the PHC website, creating a comprehensive and unique signposting resource for plant health information with relevance to Scotland.

 

Forestry, Horticulture, Agriculture, Environment | Final Report and Policy Document

The use of mobile technology to enhance plant health monitoring and awareness in Scotland

August 2019

The aim of the project was to review existing websites and smartphone apps currently available and applied in the plant health sector and to assemble a detailed overview covering the following points:

  • What options are available in terms of mobile software applications for plant health?
  • What is their primary purpose?
  • Who is the target audience (growers, plant health professionals, citizen science, …)?
  • Which plant health sectors do they cover?
  • Are they reliable and accurate?
  • Is information submitted to a central database? If so, how is this information used?
  • Could they be used globally, or are they limited to certain geographic regions?
Horticulture, Agriculture | Policy Document

Impact on Scottish crops if the molluscicide metaldehyde is withdrawn

December 2018

This report sets out estimates for the crop loss and value to Scottish crop production should the molluscicide metaldehyde be withdrawn. This would leave ferric phosphate as the only available chemical control option. Short term losses are negligible as the substitution of ferric phosphate carries no additional treatment costs and has equivalent efficacy. Longer term there is some risk should resistance arise to this single site mode of action active, and ferric phosphate (although of lower mammalian toxicity to metaldehyde) has some environmental impacts of its own.

Difficult choices to protect gardens and the environment

Authors: Katy Hayden
September 2018

Heritage gardens play an important role in plant conservation. They house collections gathered over decades or even hundreds of years, including varieties of plants that may be overlooked elsewhere, fostering heirloom varieties and preserving biological diversity that is the raw material of adaptation. As well as being beautiful and tranquil sites of cultural heritage, these ex-situ resources are treasure troves of biological diversity. Arduaine Gardens shows us that tough choices can be necessary and important to preserve these collections and the surrounding environment.