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Sarah Pethybridge

Sarah Pethybridge

Assistant Professor

211 Barton Laboratory
(315) 787-2417

The primary goal of my program is to provide reliable information to vegetable growers and industry stakeholders in New York to encourage adoption of durable management strategies and tactics for the control of soilborne diseases.

Research Focus

The primary research goal of my program is to conduct novel studies which advance foundational knowledge surrounding pathogen biology and quantitative epidemiology that enable transformational step-changes within plant pathology.

My research program is founded within the areas of quantitative epidemiology and disease management, and centers on using the principles of decision theory to underpin the strategic and tactical decisions made by growers to control plant diseases, to minimize crop loss, and improve profitability and productivity. In the absence of information modelling the relationships between crop damage and yield loss, growers and stakeholders often adopt a prophylactic approach to disease control due to their highly risk averse nature and risk of incurring substantial losses. Decision theory aims to decrease the frequency of false positive decisions (i.e. application of a pesticide for disease control when not economically warranted) and reduce the negative environmental impacts of pesticides which often pose a significant risk of off-target effects and deleterious human health consequences. While, these decisions are inherently a function of the social context of formation for risk perceptions, my research aims to quantify the probability (i.e. uncertainty) surrounding these decisions and provide robust recommendations on the likelihood of the utility of a broad range of strategies and tools to underpin these decisions. Judicious use of pesticides for plant disease control will lead to reduced variable costs of production by growers and stakeholders, which directly impacts upon profitability and productivity and therefore improves the diversity and resilience of the agricultural production systems supporting small farming communities in rural New York.

Outreach and Extension Focus

The primary goal of my extension program is to provide reliable information to vegetable growers and industry stakeholders to encourage the adoption of durable management strategies and tactics for the control of soilborne vegetable diseases in New York.

My extension activities are underpinned by the Diffusion of Innovations sociological theory described by Rogers (2003). Herein diffusion is defined as “the process in which an innovation is communicated through certain channels over time among the members of a social system”. Moreover, an innovation is defined a piece of knowledge that reduces the uncertainty in decision making.

In collaboration with Cornell Cooperative Extension, I aim to have a comprehensive knowledge of the sociological framework and drivers that are central to reducing the uncertainty associated with the decision of a grower to adopt a new finding or tool from my research program. Uncertainty is often a common reason preventing or reducing the rate of adoption of a finding because of the perceived negative consequences. The probability of negative or unintended consequences from the adoption of our findings is decreased by having a comprehensive understanding of the agronomic management and markets of the vegetable crops in which I collaborate. Uncertainty is reduced by valuing communication channels and the development of rapport with the intended audience to ensure my extension program is founded in conversations rather than communication. The network by which disease management decisions are made within the processing and large-scale vegetable industry in New York is unique in that it represents a strong link between growers and stakeholders that have a direct interest in obtaining high quality and yield. Crop scouts and agronomists are often employed by the stakeholders or private companies to provide growers with advice on agronomic inputs.

Teaching Focus

My primary goal of teaching is to be a source of accurate and reliable information to students that is portrayed with clarity and is transferred in an engaging and diverse format to encourage discussion and self-learning.


I do not have a formal teaching appointment at Cornell University but prior to my appointment have considerable experience teaching introductory plant pathology, quantitative epidemiology (graduate level), and integrated crop health management. I was also awarded a Teaching Merit Certificate following nomination by my undergraduate students from the introductory plant pathology class (see curriculum vitae).

Since my appointment, I have participated in three years of the Field Plant Pathology Course (PLPA/ENTO 4190) and co-taught and accompanied field trips on processing vegetable production with Professor Brian Nault (Entomology) and Dr. Julie Kikkert (Cooperative Extension Regional Vegetable Team Leader). In both years, approximately 30 undergraduates enrolled in the Summer Scholars Program at the New York State Agricultural Experiment Station, Geneva, and graduate students from the Plant Pathology & Plant-Microbe Biology Section have participated.

I have also contributed as a guest lecturer to HORT 3500 (Principles of Vegetable Production; Professor Steve Reiners, Horticulture) providing an overview of the disease triangle concept and management principles using examples from my research and extension program.

I seek to present information in diverse formats in recognition of the variability in learning. I also encourage instructive discussions with students to promote self-learning and diffusion of principles between students. Where possible, I use new technologies often developed within my own program (e.g. Leaf Doctor app for quantifying disease severity) to illustrate key principles.

Awards and Honors

  • Schwartz Research Fund Graduate Student/Postdoc Travel Award (2018) Schwartz Research Fund, Cornell University
  • Affinito Stewart Award (2015) Presidents Council for Cornell Women
  • American Phytopathological Society Syngenta Award (2010) American Phytopathological Society
  • Award for Outstanding Graduates (2004) University of Tasmania, Australia
  • Teaching Merit Certificate (Individual) (2004) University of Tasmania, Australia

Selected Publications

Journal Publications

Presentations and Activities

  • Improving the management of white mold in snap bean. Mid-Atlantic Fruit and Vegetable Growers Convention. January 2017. Hershey, Pennsylvania, USA.
  • Concepts of plant pathology and disease management in vegetables. Winter vegetable school - Orleans County. February 2015. Cornell Cooperative Extension. Albion, NY.
  • Concepts of plant pathology and disease management in vegetables. Winter vegetable school - Niagara County. February 2015. Cornell Cooperative Extension. Lockport, NY.
  • Concepts of plant pathology and disease management in vegetables. Winter Vegetable School - Erie County. February 2015. Cornell Cooperative Extension. East Aurora, NY.
  • Root crop disease update from down under! Empire Expo. January 2015. Cornell Cooperative Extension. Syracuse, NY.
  • Towards a durable management strategy for white mold in New York vegetable production. Empire Expo. January 2015. Cornell Cooperative Extension. Syracuse, NY.
  • Unravelling the spectrum of diseases affecting lima bean in New York. Empire Expo. January 2015. Cornell Cooperative Extension. Syracuse, NY.
  • Concepts of plant pathology and disease management in vegetables. Finger Lakes Production Auction Group. January 2015. Cornell Cooperative Extension. Penn Yan, NY.