Career Summary
1999 - present Plant Pathologist (Epidemiology)
Hop and pyrethrum pathology
Research (70%) / Extension (30%)
Contributions to the teaching program when required
2001-2002 Vice-Chair of the American Phytopathological Society’s (APS) Epidemiology Committee
2002-2003 Chair of the APS Epidemiology Committee
2001-2003 Secretary/Treasurer of Australian Institute of Science and Technology (AIAST) – Tasmanian Branch.
2003 - Executive Committee of Australian Institute of Science and Technology (AIAST) – Tasmanian Branch.
2004 1st ISHS International Humulus Symposium
Scientific Committee (Senior Editor for Acta Horticulturae)
2005 - Senior Editor: APSnet Education Centre
Advanced Topics – Population Genetics/Epidemiology
Research Activities
I am responsible for the research and extension programs on hop and pyrethrum pathology of the Tasmanian Institute of Agricultural Research. The extension component involves the development of an education program using traditional and innovative communication technologies for industry personnel and growers. The research component is integrated with, and supportive of, the extension component. Current research focuses on the important diseases of hops in Australia (viruses, viroids, and fungi) and pyrethrum (fungi and viruses) in Tasmania with the overall objective of developing and/or improving integrated pest management programs. As a part of this program, risk analyses are also conducted on the threat of exotic pathogens to these industries. Research is supported by national funding programs (Australian Research Council) and industry (Australian Hop Marketers and Botanical Resources Australia Pty. Ltd.).
Hops: This project focused on the diseases (hop mosaic carlavirus, HpMV; hop latent carlavirus, HpLV; and Prunus necrotic ringspot ilarvirus, apple, PNRSV-A; and intermediate, PNRSV-I), and hop latent viroid (HLVd) infecting hop (Humulus lupulus L.) in Australia, and diseases which may pose a risk to the Australian hop industry in the future. This project was funded by the Australian Research Council and Australian Hop Marketers, through the Strategic Partnership in Industry and Training program. Additional funds were also been sourced from the Australian Academy of Science’s Young Career Researcher Exchange program to facilitate the development of stronger collaborations with the hop pathology program of Washington State University at Prosser and resulted in studies detailing the risk of hop downy and powdery mildew to the Australian hop industry. These studies involve the continual assessment of the effect of viruses on the yield and quality of newly adopted hop cultivars in Australia and the rate of virus re-infection after planting with virus-free material. Studies are continuing on the elucidation of mechanisms of virus transmission in Australian hop gardens.
Pyrethrum: Our work on pyrethrum diseases involves quantifying the spectrum of fungal plant pathogens found on pyrethrum foliage and their relative impact on yield and pyrethrin assay. For those fungi having a significant impact on production (such as Phoma ligulicola) we are conducting detailed epidemiological studies to determine how disease levels change with environmental parameters and geographical factors (geophytopathology). This section of the work involves collaboration with Professor Forrest Nutter and Mr. Paul Esker at Iowa State University, USA. This study will develop radiometric technology for disease assessment in pyrethrum and predictive models for disease development based on environmental conditions and furthermore, assess the effect of simulated climate change events on disease severity in the future. Funds have also been sourced from Agriculture, Fisheries and Forestry Australia (AFFA) to conduct surveys and risk analyses for viruses and viroids to the pyrethrum industry. This information will be combined with work completed as part of a study tour of pyrethrum production in Kenya (funded in part by HAL). The overall objective of this program is to develop a durable management strategy for foliar diseases of pyrethrum. Our industry partner in this program is Botanical Resources Australia Pty. Ltd.
Research Interests
Quantitative Epidemiology:
Forecasting of plant diseases
Identification of site-specific risk factors for disease (geophytopathology)
Spatio-temporal analysis of epidemics
Measures of association between pathogens
Disease management
Use of molecular markers for population genetics to assist in epidemiological knowledge of pathosystems
Biometrics
Selected Publications:- Pethybridge, S.J., Esker, P., Hay, F.S., Wilson, C.R. & Nutter, F.W. Jr. , 2005, 'Spatiotemporal description of epidemics caused by Phoma ligulicola in Tasmanian pyrethrum fields', Phytopathology, 95, pgs. 648-658
- Pethybridge, S.J., Madden, L.V., Griggs, J. & Wilson, C.R. , 2004, 'Species composition and abundance of aphids in Australian hop gardens and their impact on spatiotemporal patterns of carlavirus epidemics', Plant Pathology , 53, pgs. 498-507
- Pethybridge, S.J., Wilson, C.R. & Leggett, G.W. , 2004, 'Incidence and effect of viruses on production of two newly adopted hop (Humulus lupulus) cultivars in Australia.', Australian Journal of Agricultural Research , 55, pgs. 765-770
- Pethybridge, S.J., Scott, J.B. & Hay, F.S. , 2004, 'Genetic relationships among isolates of Phoma ligulicola from pyrethrum and chrysanthemum based on ITS sequences and its detection by PCR.', Australasian Plant Pathology , 33, pgs. 173-181
- Pethybridge, S.J. & Madden, L.V. , 2003, 'Analysis of Spatio-temporal Dynamics of Virus Spread in an Australian Hop Garden by Stochastic Modeling', Plant Disease , 87, pgs. 56-62
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