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© 2003 Plant Management Network.
Published 13 November 2003.


Managing Risk to Minimize Crop Loss: Introduction to the Symposium Proceedings


William W. Turechek, ex-chair Plant Disease Losses Committee, Dept. of Plant Pathology, NYSAES, Cornell University, Geneva, NY 14456


Corresponding author: William W. Turechek. wwt3@cornell.edu


Turechek, W. W. 2003. Managing risk to minimize crop loss: Introduction. Online. Plant Health Progress doi:10.1094/PHP-2003-1113-01-RV.


In production agriculture, the potential for catastrophic loss due to plant disease is always present. Growers are acutely aware that their everyday horticultural and pest management practices, as well as daily weather events, place them at risk for major losses due to one or more endemic, or possibly invasive, pathogens. The choice of variety, insufficient or poorly implemented pest management practices, and the development of pesticide resistance, just to name a few, are all perceived as factors contributing to the level risk growers face. As pathologists, we should be asking the question: To what degree are these risks measurable (or at least observable), predictable or manageable?

Quite simply, risks can be assessed and measured by direct observation. If we have a more comprehensive understanding of the factors contributing to the risk we can develop and apply mathematical or statistical models to either measure or, more importantly, predict or forecast risk. No matter how risks are quantified, they are generally expressed as a probability relative to the occurrence of a set of conditions. Assuming that (at least some) risk can be predicted, risk management falls upon the actions of the end user (i.e., the grower), their confidence in the forecast, and their overall tolerance for accepting risk.

In these proceedings, approaches to assessing, predicting and managing risk in production agriculture and international trade are addressed. This set of papers follows a symposium organized by the Plant Disease Losses and Regulatory Committees of the American Phytopathological Society for its 2002 Annual Meeting held in Milwaukee, WI.

The first paper, contributed by Xiao Bing Yang, is an introduction to the concepts of risk assessment and risk prediction. He reviews and clarifies risk assessment terminology and discusses the practical application of and identifies research gaps in both the assessment and prediction of risk in the context of plant disease management. Next, Dennis Gonsalves and Steve Ferreira discuss the development and commercialization of transgenic papaya resistant to Papaya ringspot virus (PRSV) in Hawaii. This is perhaps the most successful application of transgenic (genetically modified) plants in commercial agriculture for disease control. The authors briefly review the circumstances that motivated their efforts and show how growing transgenic papaya is beginning to help growers produce nontransgenic papaya in Hawaii.

National and international trade is a major component in the daily business of modern day agriculture. One of the greatest risks associated with trade is the unintentional introduction and movement of pathogens on plant material (or produce) across state and country borders. Larry Brown discusses the role of USDA-APHIS-PPQ and the New Pest Advisory Group (NPAG) in tracking and assessing the risks of exotic plant pest introductions in U.S. agriculture. Gareth Hughes then introduces the concept of the “maximum pest limit” as a practical method of implementing quarantine security measures against the import of invasive pest species of plants.

On the risk prediction front, Jonathan Yuen discusses the role of forecasting in the management of plant disease. He follows by introducing Bayes’s theorem and shows how bayesian approaches to plant disease forecasting are used to evaluate and then refine plant disease forecasters. And lastly, Walter Mahaffee et al. discuss and critically evaluate the approaches undertaken in rapidly responding to the powdery mildew epidemic that hit the hop industry in the Pacific Northwest. They discuss how government, industry, academic, and grower partners came together to establish an internet-based network for delivering regional warnings based on an adaptation of the Gubler-Thomas powdery mildew risk prediction model for grape.

Many funding agencies, particularly those directly serving agriculture, are beginning to require documentation of how the proposed research will impact or benefit the stakeholders. The reduction of risk is one such measurable impact. These proceedings cover a wide range of topics under the umbrella of what is considered risk assessment and prediction. As will become evident, there are many levels to a risk assessment. Risks are tangible, sometimes easily measurable, predictable, and certainly manageable. We hope that these proceedings will help pathologists realize that risk assessment is not merely an abstract statistical concept researchable only by those versed in statistics and will encourage pathologists to employ the techniques of risk assessment in their research.


Symposium Papers


Risk Assessment: Concepts, Development, and Future Opportunities

X. B. Yang


Transgenic Papaya: A Case for Managing Risks of Papaya Ringspot Virus in Hawaii

Dennis Gonsalves and Steve Ferreira


Analyzing Positive Finds with Explicit Uncertainty

Lawrence G. Brown


The Maximum Pest Limit Concept Explained

Gareth Hughes


Bayesian Approaches to Plant Disease Forecasting

Jonathan Yuen


Responding to an Introduced Pathogen: Podosphaera macularis (Hop Powdery Mildew) in the Pacific Northwest

Walter F. Mahaffee, Carla S. Thomas, William W. Turechek, Cynthia M. Ocamb, Mark E. Nelson, Alan Fox, and Walter D. Gubler