Ecology, Efficacy, and Impact: biological control of Himalayan balsam

Overview

Biological invasions by alien species are regarded as one of the top five direct drivers (together with habitat destruction, over-exploitation, climate change and pollution) of recent global biodiversity loss, according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. The impacts of alien species are linked to the declining conservation status of threatened species, and their accelerated spread into protected and biodiverse habitats are a major global concern. Riparian habitats are one of the richest and most complex habitats globally. However, encroachment and establishment of invasive alien species pose additional challenges to the unique flora and fauna, as well as ecosystem function, of these freshwater habitats.

Impatiens glandulifera, Himalayan balsam, is an annual plant native to the western Himalayas, prolific along waterways. It is listed under Schedule 9 of the Wildlife and Countryside Act 1981, therefore it is an offence to plant or otherwise cause this species to grow in the wild. Himalayan balsam, by forming tall, dense colonies, shades out and results in the extirpation of native vegetation. This species is notoriously difficult to manage, particularly if an adjacent water way provides a constant input of viable seeds. In 2014, a biological control agent, rust fungus Puccinia komarovii var. glanduliferae var. nov, was approved for release in the EU. The rust fungus was deployed at various sites from 2015 to better manage I. glandulifera in the UK by the Centre for Agriculture and Bioscience International (CABI).

CABI found that results from inoculated populations of I. glandulifera were variable, with low levels of infection observed in the field. Subsequent inoculation experiments conducted under controlled conditions, revealed significant variation in the susceptibility of plant populations to the rust, with some showing immunity (no infection observed). Further study by CABI showed that I. glandulifera had been introduced into the British Isles on more than one occasion, from multiple locations within the native range and therefore different variants of the rust fungus are needed. Further studies have shown an indication of overwintering of the fungus in suitable conditions. However, more information is needed to identify which factors are most suitable for the rust fungus in the field (rather than in controlled environments). Although there is also an indication that the rust fungus may spread naturally from the initial release site, little is known of the timing and efficacy of natural spread.

The aim of this project is to assess the in-situ drivers of rust fungus infection success of I. glandulifera and develop a modelling and monitoring framework to determine the natural dispersal efficacy of the rust fungus to other invaded sites.
Specifically, the project objectives are to:
1) Determine the key environmental variables that impact the efficacy of rust fungus infection and survival in-situ.
2) Undertake an assessment of the impact of the rust fungus on I. glandulifera seed production as a determinant of biological control success in managing invaded areas.
3) Determine the efficacy of drone imagery in assessing reduction in population size of infected I. glandulifera populations and determining infection status of I. glandulifera populations.
4) Assess the natural dispersal capabilities of the rust fungus using a spatial modelling approach

Methodology

The project will be carried out in collaboration with the Tees Rivers Trust, with advice provided by Centre for Agriculture and Bioscience International (CABI). Therefore, the student will be working in partnership with these colleagues when designing and implementing survey protocols of the rust fungus. This partnership will also be working to establish a long-term monitoring regime which will extend beyond the PhD.
Methods:
1) The student will undertake a full site assessment, mapping key topographical features of the invaded riparian sites and catalogue flora present at the site using botanical survey methodology
2) In order to understand the environmental conditions conducive to the rust fungus growth and infection rate, variation in environmental conditions using data loggers will be assessed over time.
3) One of main drivers of I. glandulifera’s success is its large seedbank. Therefore, the student will conduct a germination trial. Soil cores will be taken at inoculated and control sites to assess the impact of the rust fungus on seed production. Soil cores will be germinated in polytunnels at Newcastle University.
4) The student will complete three seasons of fieldwork to monitor the rust fungus efficacy via infection rate in the field, documenting I. glandulifera population size. The student will also test monitoring via drone image capture and analysis. This will be correlated with the on the ground data capture as a potential approach for monitoring larger scale spread of the rust fungus.
5) To assess the natural spread potential of the rust fungus to other invaded riparian sites, the student will develop an individual-based spatial model, considering fluvial connectivity of the catchment area and populations of I. glandulifera in the catchment.

Project Timeline

Year 1

Literature review as a meta-analysis to assess biological control efficacy globally (months1-4); prepping for fieldwork, mapping site features, soil core collection (months 5-6); spring community and success of infection survey (month 7); drone flight course and testing (months 8-10); summer community and environmental conditions survey (months 11-12)

Year 2

Data management and modelling method assessment (months 13-16); soil core collection, set up germination experiment months (months 17-18); spring community assessment (month 19); drone flights and image analyses (months 20-22); summer community and environmental conditions survey (months 23-24)

Year 3

Data collection from germination experiment (Months 25); Data analyses, writing up results (months 26-30); Writing thesis chapters, attendance at an international conference (months 31-36)

Year 3.5

Writing publications and thesis submission (months 37-42)

Training
& Skills

The student will receive training from an interdisciplinary supervisory team, particularly in some of the key NERC most wanted skills:
*Fieldwork: the large fieldwork element of this PhD means the student will be exposed to a variety of sampling and experimental techniques in the field
*Taxonomic Identification: to create an inventory of flora the student will receive species ID training, particularly botanical.
*Data management and modelling: the student will be part of the Modelling, Evidence and Policy Research group at Newcastle and as such will have the opportunity to learn an array of modelling methods best suited to their data.
*Translating research into practice: As the output of this PhD will be integral to management of invasive species, the student will receive training in science communication to multiple audiences (e.g. policy makers, non-governmental organisations (NGOs) and the wider public).

The student will also participate in IAPETUS training and events. A training budget is included for any external training required by the student

References & further reading

https://www.cabi.org/projects/biological-control-of-himalayan-balsam/
Podcast on the biological control of I. glandulifera invasiv.es/3ns3R9G

Further Information

For further information please contact Dr Aileen Mill
Aileen.mill@newcastle.ac.uk

Apply Now