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: Daniel Chapman
Xylella fastidiosa is a bacterial plant pathogen that can cause disease in a broad range of hosts. Disease symptoms include leaf scorch, wilting of foliage, dieback and plant death. Xylella fastidiosa was first detected in Europe in 2013 in Puglia in Italy and was identified as subspecies pauca which has gone on to devastate olive plantations in this region. 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, an outbreak would have serious impacts on any businesses where Xylella is detected and the wider environment. An essential aspect of ensuring that Xylella is not introduced to Scotland is to establish, through modelling, that national surveillance monitoring aimed at detecting a Xylella outbreak is effective. In addition, it is important to identify which epidemiological parameters most strongly influence the effectiveness of surveillance, to guide where future empirical research should be targeted to reduce any uncertainty.

Impact: This project will contribute to Scottish Government’s preparedness measures for the possible arrival of Xylella fastidiosa by ensuring surveillance monitoring is effective and by identifying the key knowledge gaps for effective surveillance.
Project Lead: Andy Evans
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. There is an urgent need to quantify the impact on Scottish plant health that will arise from pesticide withdrawal scenarios and to set this in the context and time frame of alternative management tools. This will be used to inform recommendations on pesticide strategy at the Scottish, UK and EU levels going forward. A synthesis report of available information is required to identify products at risk and work through scenarios for the plant types, pests and diseases of importance in Scotland. This will be a project where cross-sectoral dialogue between the plant health sectors of agriculture / crop production, horticulture, forestry and the environment will be necessary. The project will review existing information and a key output will be summary recommendations appropriate for use by policy makes. The bid must include time to engage with in cross-sectoral dialogue and with Scottish Government staff to discuss and progress early drafts.

Impact: Improved understanding of costs and benefits of pesticide use across Scottish sectors and an impact analysis for the most likely withdrawal scenarios such that key gaps can be identified and their impact quantified in order to inform pesticide policy.
Project Lead: Adam Kleczkowski
The movement of plant pests and pathogens into Scotland in likely to increase in the coming years, e.g. due to changes in trade, potentially increasing from outside Europe following Brexit, while their spread and severity could be affected by climate change (both positively and negatively). It is therefore vital that we understand the role of climate on the impacts of such pests and diseases across the whole of Scotland, in relation to the distribution of plant hosts, allowing us to target potential control options on the main threats. To allow plant health professionals and others to assess such impacts in as straight forward a way as possible, web- / desktop-based tools are needed that offer quick and easy access to complex computer models. These models should be as comprehensive as possible, allowing new information on pests, pathogens and their hosts to be added as it becomes available.

Impact: Easily accessible tool for stakeholders and government plant health officials to assess possible impacts of climate on pests and pathogens in Scotland.
Early scoping of plant health priorities with key Scottish stakeholders and discussions at the PHC launch event indicate a complex landscape of plant health information sources, confusion amongst stakeholders and a perception of information overload. To inform future KE methods and priorities, a network analysis is required to identify the sources of information and the strength of their effect on Scottish stakeholder communities.

Impact: Improved understanding of concepts and options amongst the Scottish stakeholder community; a basis for gap analysis by the PHC.
Project Lead: Steve Woodward
Discussions at the PHC launch event, and between sector leads, indicate some distinctive and different approaches to tackling pests and diseases in Scotland are to be found across sectors and between businesses/units. Some focus on direct interventions (e.g. use of chemicals), whilst others have largely considered indirect interventions (e.g. manipulation of age structures), and understanding of integrated approaches is patchy. There is an opportunity to gather together a guide to the different approaches – which could propose a typology and set of definitions of solutions that could be used by subsequent PHC communications; provide a basis for cross-sectoral dialogue; provide a basic mapping of how the solutions are currently used by sector; and help identify untested combinations of solution and setting which could be developed.

Impact: Improved understanding of concepts and options amongst stakeholder community in
Scotland; a basis for gap analysis by PHC.
Project Lead: Sebastian Raubach
Plant health is a major issue worldwide with many different pests and diseases threatening different plant-based sectors, e.g. forestry, agriculture, environment and horticulture. Keeping up to date with such threats has always been a major task in terms of pest and disease identification, geographic spread, monitoring and coordinating responses etc. yet, in the world of mobile technology, we now have an opportunity to achieve some of these things from apps on our phones. Questions around the use of such technology include: What options are available in terms of mobile technologies for plant health?; What is their primary purpose?; Who are they targeted towards - farmers, plant health professionals, citizen scientists etc? Are they accurate and reliable? Do they provide real time information to a central database?; Who uses such a database?; Which sectors are they designed to work in or are they cross sector?; Do they have global use or are they limited to certain geographic regions? A review of such technologies is needed to ascertain which are most appropriate for use in Scotland across a range of sectors, which could be further adapted to achieve this aim and, if further development is required, what are the key elements of such a technology that would need to be incorporated into such a mobile application?

Impact: Improved risk assessment; better equipped stakeholders and government plant health officials; improved coordination of plant health activities in Scotland.
Project Lead: Kevin Watts
Xylella fastidiosa is a bacterial plant pathogen that can cause disease in a broad range of hosts. Disease symptoms include leaf scorch, wilting of foliage, dieback and plant death. Xylella fastidiosa was first detected in Europe in 2013 in Puglia in Italy and was identified as subspecies pauca which has gone on to devastate olive plantations in this region. 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, an outbreak would have serious impacts on any host plant-related activities/businesses and the wider environment. An essential aspect of ensuring Scotland’s preparedness for the possible arrival of Xylella is to prepare a risk map for the likelihood of the arrival of Xylella together with the consequences for key elements of the Scottish economy (directly and indirectly impacted) in the event of an outbreak. Data relevant to the risk mapping for Scotland would include location of sites involved in plant imports, volume of plants imported, impact on business trading in plants if an outbreak is detected and the wider environmental impact.

Impact: This project will contribute to Scottish Government’s contingency and preparedness measures for the possible arrival of Xylella fastidiosa by mapping the risk of likelihood and impact of an outbreak.
Project Lead: Kirsty Park
Xylella fastidiosa is a bacterial plant pathogen that can cause disease in a broad range of hosts, including Polygala myrtifolia, Olea europaea, Rosmarinus Officinalis, Lavandula sp., Prunus sp. and Nerium oleander. Disease symptoms include leaf scorch, wilting of foliage, dieback and plant death. Xylella fastidiosa was first detected in Europe in 2013 in Puglia in Italy and was identified as subspecies pauca which has gone on to devastate olive plantations in this region. There are currently major Xylella outbreaks in Southern France, including Corsica, Italy, mainland Spain and the Balearic Islands. The bacteria are transmitted by xylem feeding insects from the Cercopidae family, which include froghoppers and spittlebugs.

There are several species of insects that could vector Xylella fastidiosa in the UK including the meadow spittlebug (Philaenus spumarius), which is very common in Scotland. An outbreak of Xylella in Scotland would have serious impacts on the affected grower/nursery and any other host plant-related activities/business within a 5km buffer zone. Therefore, in order to establish the potential for these bacteria to spread, should they be introduced, it is important to identify and get an understanding of the abundance of potential Xylella vectors in Scotland. The WrEN project (http://www.wrenproject.com/), presents a unique opportunity to make use of existing insect collections to map the occurrence of potential Xylella vectors within agricultural woodlands across Scotland. Since 2013, partners on the WrEN project have surveyed over 130 secondary and ancient woodland sites for habitat and wildlife in two regions of mainland Britain. To date, over 1100 species have been recorded from a wide range of taxa. Vegetation structure has been characterised at all sites including information on tree species richness, tree density and size, understorey and canopy cover. In addition, the surrounding landscape has been mapped at a range of spatial scales up to 3 km from each site.

Impact: This project will contribute to Scottish Government’s preparedness measures for the possible
arrival of Xylella fastidiosa by identifying and mapping the distribution of potential vectors of Xylella
in Scotland.
Project Lead: Fiona Highet
The unexpected finding of the presence of Lso and a potential vector species in Scotland raised significant concerns (Sjolund et al. 2017). However, without further information this cannot be put into context. The likelihood is that the disease and possible vector have been present in Scotland for a long time, and yet our crops remain symptomless. Therefore, without the introduction of another vector risk may remain low. In order to confirm this and establish the current risk of transmission to crops, the following information is urgently required: the distribution of potential pyllid vectors including T. anthrisci in regions of Scotland, the presence of Haplotype C Lso within these vectors, a genomic comparison of the Scottish Haplotype C Lso with disease-causing Haplotype C Lso from Finland and Spain, and establishment of T. anthrisci’s vector potential through the development of a breeding colony.

The knowledge required to identify different psyllid species is highly specialised but is essential in order to gain a wider understanding of the disease threat that such insects cause. As few in Scotland have this specialisation (including SASA), it is deemed important to up-skill others by running a training course on psyllid identification for entomologists within Scottish organisations to better enable Scotland to deal with possible Lso threats both now and in the future.

Impact:
This project will contribute to Scottish Government’s ability to control pests / diseases by increased knowledge on the presence and distribution of Liberibacter solonacearum and its host psyllids in Scotland and the potential of these organisms to cause and spread disease.
Project Lead: Fiona Burnett
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.

Publications

Horticulture, Agriculture | Policy Document

Impact on Scottish crops if the molluscicide metaldehyde is withdrawn

January 2019

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.