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: Arthy Surendran
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.
Project Lead: David Cooke
Species of the genus Phytophthora are of particular concern to the health of Scotland’s plants due to their destructive potential and ability to spread via cryptic infection on traded plants. The genus Phytophthora currently comprises over 200 species and there is a current gap in the evidence in estimating and acting on these threats in a proportional and measured manner to both prevent further imports of Phytophthora and to objectively assess the risk of any new findings.

This project will (i) review and collate the contemporary data and evidence on Phytophthora discovery, species description and traits; (ii) use the collated data to horizon-scan and predict disease threats in Scotland and (iii) model and map the greatest threats to plants in specific key habitats. The findings will be compiled into a report on the updated risks with recommendations for enhancing preparedness through risk-based prioritisation of hosts and habitats for targeted surveillance to promote earlier detection of Phytophthora species. Although the project will consider plants in agriculture, forestry, horticulture and natural ecosystems across Scotland, the principal focus will be on the risks to relatively under-studied plant hosts in the natural environment.

This project was selected for funding from the Project Call: “Enhancing preparedness against pests and diseases: plugging evidence gaps for Scotland”.

Image credit: Glensaugh ©The James Hutton Institute
Project Lead: Matt Elliot
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.
There is a clear need to present consistent and focused notifiable pest management information to Professional Operators. There is good information available, however it is in a variety of formats and the quality and type of information is variable. The purpose of this project is to explore if pest information can be set out in a consistent format to support Professional Operators by presenting bespoke plant biosecurity information for their site and associated operations. This information aims to enable Professional Operators to focus their attention on the critical analysis processes required to establish effective plant biosecurity systems.

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
Project Lead: Harry Watkins
PHC2022/06 builds on an outcome from a previous PHC project (PHC2019/05) which created GIbase 1.0: A database of green infrastructure plant species in England and Scotland, which was built by searching local authority planning portals for plant specifications associated with Green Infrastructure projects.

This project will extend the database, creating GIbase 2.0., establishing search functions for planning portals across Scotland, automatically generating notifications of projects that meet specific criteria relating to project scale and type. This will allow both higher resolution data to be recorded and also ensure that GIbase 2.0 captures the most current schemes under development or in early-stage planning.

This project will Map the diversity and abundance of plant species used in green infrastructure across Scotland, and record this data in GIbase 2.0. It will use the UK PHRR to create relative risk profiles for each plant species, and, for commonly planted species, create high quality data sheets using published research, providing a valuable asset to policy-makers, local planning authorities, Green Infrastructure designers and developers.

This project was selected for funding from the Project Call: “Enhancing preparedness against pests and diseases: plugging evidence gaps for Scotland”.
Project Lead: Daniel Bebber
PHC2022/05 will take a unique cross-disciplinary approach using biophysical risk modelling combined with social science methods to analyse the threat from emerging plant health threats to both arable and horticultural crops in Scotland.

This project was selected for funding from the Project Call: “Enhancing preparedness against pests and diseases: plugging evidence gaps for Scotland”.
From this project there will be an improved understanding of potential risks from plant pathogens under future climate scenarios to inform future priorities for pathogen detection and surveillance efforts. The biophysical modelling will be added to with qualitative data from existing Scottish Government funded stakeholder consultation research.

The project will also identify knowledge gaps for further research, such as in biology, host distributions, and other biophysical factors influencing pathogen spread as required by the model, as well as a shared understanding with stakeholders of priority concerns regarding future plant health risks.
Project Lead: Helen Rees
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.
Project Lead: Henry Creissen
Previous research shows that better informed farmers and agronomists can make better IPM decisions and score higher in IPM metrics (PHC2020/05). Research has also identified that decision making on farm is often shared between the farm agronomist and the farmer. However, there is a knowledge gap on how factors influencing IPM scores link to available impact metrics such as pesticide usage.

This project will look to improve the flow of IPM knowledge and its uptake to increase the resilience of Scotland’s crops to pests and diseases, whilst reducing reliance on pesticides.

The drivers and barriers to further adoption of IPM practices for different decision makers and for different farm types will be identified, improving the ability to tailor IPM research and knowledge transfer and exchange activities to consider, if not overcome, those barriers and improve uptake.
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

Publications

Horticulture, Agriculture | Final Report and Policy Document

Interdisciplinary Analysis of Plant Health Threats to Arable and Horticultural Crops in Scotland

July 2024

This project took a unique cross-disciplinary approach using biophysical risk modelling combined with social science methods to analyse the threat from emerging plant health threats to both arable and horticultural crops in Scotland.

Horticulture, Agriculture | Final Report and Policy Document

Understanding crop producers’ perceptions around crop health decision making and the impact of that on key metrics such as pesticide usage

July 2024

Increased uptake of Integrated Pest Management (IPM) measures on Scottish farms will be key in improving resilience against pests, weeds, and diseases, and maintaining or improving crop yields and farm profitability, whilst reducing environmental impact and reliance on pesticides. The aim of this project therefore was to improve the flow of IPM knowledge and its uptake and identify the drivers and barriers to further adoption of IPM practices for different decision makers and for different farm types.

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

Biosecurity for plant health: better justification of precautionary measures

May 2024

This project engaged experts and practitioners with knowledge of existing sectoral practices in Scotland, UK and internationally, summarised existing literature and undertook a gap analysis, to generate a better understanding of the rationale for taking precautions and to improve the evidence base with which to justify taking actions.

Forestry, Horticulture, Agriculture | Final Report and Policy Document

Potential of biocontrol for the sustainable management of plant diseases in Scotland: opportunities and barriers

March 2024

Previous PHC projects identified biocontrol as a major element 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 (including regulatory).

Forestry, Horticulture, Environment | Final Report and Policy Document

Action Research to gain a deeper understanding of large-scale biosecurity risks to Scotland

December 2023

This project has developed a systems approach, in the context of plant health biosecurity risks in the retail, infrastructure landscaping and planting in the natural environment, to facilitate further understanding of key organisations and identify general and specific leverage points at which interventions could have a significant effect on the system.

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

A targeted analysis of the impact of insecticide withdrawals in Scotland, in the context of alternative control options

July 2023

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.  This project analysed current crop production patterns and insecticide use in combination with how likely different insecticides are to be withdrawn and provided stakeholder views on the impacts of any such losses on their industry, including other control methods that may be adopted.

PHC Annual Report 2022-2023

July 2023

The Plant Health Centre works with Scottish Government, public bodies and stakeholders to provide scientific evidence to help them make important decisions about pests and pathogens that threaten Scotland the most.  Over the past 12 months we have delivered a consistent programme of stakeholder engagement and project commissioning, which are detailed in our annual report. 

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

Biosecurity practices to support plant health: a review of knowledge and practice

March 2023

This research investigated plant biosecurity risks from site visitors, tools & equipment, and large machinery. In addition to reviewing published guidance, UK businesses and organisations were engaged via questionnaires and interviews to explore how these aspects of biosecurity are understood and what procedures may be in place to address them.

Forestry, Horticulture, Environment | Final Report and Policy Document

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

March 2023

This research focussed on two areas of biosecurity that provide significant risk to plant businesses and the wider environment in Scotland, i) plant waste management, and ii) the constituents of reduced-peat and peat-free growing media.

Enhancing the Plant Health Centre’s communication with stakeholders

February 2023

This project was commissioned to implement a selection of the recommendations made in the PHC stakeholder engagement strategy and communication plan. The team developed strategies to manage time and resources of the Plant Health Centre more efficiently regarding communication of outputs, general information on activities, aims and current issues related to plant health.

Horticulture, Agriculture | Final Report and Policy Document

Perceptions of pest risk and differences in IPM uptake by arable farmers and agronomists in Scotland

November 2022

Pesticide use remains an important tool in managing pest, weed and disease risks to crops and maintaining profitable production. There are several drivers for reducing reliance on pesticides and promoting the uptake of more sustainable practices through integrated pest management (IPM).  By identifying IPM information networks it may be possible to improve the flow of information to farmers by targeting their preferred information sources.  Better informed farmers and agronomists can make better IPM decisions.  Therefore, this project undertook a telephone survey to collect information on currently perceived invertebrate pest and disease threats in Scotland, the level of IPM uptake, and the information sources they relied upon.  

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.  The project aimed to identify priority steps to develop more useful models and tools for assessing biosecurity risks from planting in the future.

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.