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Browsing by Author "Forbes, Gregory Allan"

Now showing 1 - 11 of 11
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    Adapting disease forecasting models to coarser scales: Global potato late blight prediction
    Sparks, Adam H.; Forbes, Gregory Allan; Garrett, Karen A. (2009)
    Many predictive models of plant disease rely upon fine-scale weather data collected in hourly increments, or finer. This data requirement is a major constraint when applying disease prediction models in areas of the world where hourly weather data are unreliable or unavailable. In response to the need to apply predictive models where only coarse resolution weather data are available, we developed a framework to adapt an existing potato late blight forecast model, SimCast. We envision this type of coarser resolution model being useful in long term decision making rather than for within growing season. For long term modeling we may be satisfied with being able to estimate the magnitude of upward and downward trends.
  • Anticipating and responding to biological complexity in the effects of climate change on agriculture
    Garrett, Karen A.; Forbes, Gregory Allan; Pande, S.; Savary, S.; Sparks, Adam H.; Valdivia, Corinne; Vera Cruz, C.; Willocquet, L. (IOP Publishing, 2009)
    The effects of climate change on biological systems are complex. This is particularly apparent for multispecies systems such as plant diseases and plant-herbivore interactions where climate can affect each species individually as well as influencing the interactions between species. This article was presented in Copenhagen as part of the conference on Climate Change: Global Risks, Challenges and Decisions, held 10-12 March 2009.
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    Beyond Yield: Plant disease in the context of ecosystem services
    Cheatham, M. R.; Rouse, M. N.; Esker, Paul D.; Ignacio, S.; Pradel, W.; Raymundo, R.; Sparks, Adam H.; Forbes, Gregory Allan; Gordon, T. R.; Garrett, Karen A. (2009)
    The ecosystem services concept provides a means to define successful disease management more broadly, beyond short-term crop yield evaluations. Plant disease can affect ecosystem services directly, such as through removal of plants providing services, or indirectly through the effects of disease management activities, including pesticide applications, tillage, and other methods of plant removal. Increased plant biodiversity may reduce disease risk if susceptible host tissue becomes less common, or may increase risk if additional plant species are important in completing
  • Climate change in the high Andes: Implications and adaptation strategies for small-scale farmers
    Perez, C.; Nicklin, C.; Dangles, O.; Vanek, S.; Sherwood, S.; Halloy, S.; Garrett, Karen A.; Forbes, Gregory Allan (Champaign, Illinois, USA: Common Ground Publishing LLC, 2010)
    This article describes the effect of climate change on agriculture in the highland Andes area of Bolivia, Ecuador and Peru. Small-scale farmers in the past have adopted techniques that have helped them adapt to changing conditions of hydrology, soil, and pest and disease populations. However, the rate of variability predicted as a result of climate change may push these Andean farmers past their range of adaptability and could have major implications for social and environmental sustainability in this region. This article examines the current adaptive strategies and offers potential risk-reduction strategies for producers, rural communities and local institutions.
  • Complexity in climate-change impacts: An analytical framework for effects mediated by plant disease
    Garrett, Karen A.; Forbes, Gregory Allan; Savary, S.; Skelsey, P.; Sparks, Adam H. (Plant Pathology, 2011)
    This article describes a framework of analysis that was developed to gauge the complexity of climate change effects on ecosystem services. Specifically, these researchers examine how climate change affects plant diseases because of the important implications plant disease can have for food production. For example, drought stress, sometimes caused by an increase in global temperature and extreme weather events, can cause either an increase in susceptibility to diseases or induce resistant reactions. These reactions to climate change are very complex and important for analyzing the risk of disease for plants in all geographic areas. This research framework is intended to be used as a tool for other researchers to examine specific components in an ecosystem in order to further understand the effects of climate change.
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    Intraspecific functional diversity in hosts and its effect on disease risk across a climatic gradient
    Garrett, Karen A.; Zuñiga, L. N.; Roncal, E.; Forbes, Gregory Allan; Mundt, C. C.; Su, Z.; Nelson, R. J. (Ecological Society of America, 2009)
    The effects of host biodiversity on disease risk may vary greatly depending on host population structure and climatic conditions. Agricultural diseases such as potato late blight, caused by Phytophthora infestans, provide the opportunity to study the effects of intraspecific host diversity that is relatively well-defined in terms of disease resistance phenotypes and may have functional impacts on disease levels. When these systems are present across a climatic gradient, it is also possible to study how season length and conduciveness of the environment to disease may influence the effects of host diversity on disease risk. We developed a simple model of epidemic progress to evaluate the effects on disease risk of season length, environmental disease conduciveness, and host functional divergence for mixtures of a susceptible host and a host with some resistance. Differences in disease levels for the susceptible vs. resistant genotypes shifted over time, with the divergence in disease levels first increasing and then decreasing. Disease reductions from host diversity were greatest for high host divergence and combinations of environmental disease conduciveness and season length that led to moderate disease severity. We also compared the effects of host functional divergence on potato late-blight risk in Ecuador (long seasons), two sites in Peru (intermediate seasons) in El Niño and La Niña years, and the United States (short seasons). There was some evidence for greater disease risk reduction from host diversity where seasons were shorter, probably because of lower regional inoculum loads. There was strong evidence for greater disease reduction when host functional divergence was greater. These results indicate that consideration of season length, environmental conduciveness to disease, and host functional divergence can help to explain the variability in disease response to host diversity.
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    A metamodeling framework for extending the application domain of process‐based ecological models
    Sparks, Adam H.; Forbes, Gregory Allan; Hijmans, R. J.; Garrett, Karen A. (2011-08)
    Process‐based ecological models used to assess organisms' responses to environmental conditions often need input data at a high temporal resolution, e.g., hourly or daily weather data. Such input data may not be available at a high spatial resolution for large areas, limiting opportunities to use such models. Here we present a metamodeling framework to develop reduced form ecological models that use lower resolution input data than the original process models. We used generalized additive models to create metamodels for an existing model that uses hourly data to predict risk of potato late blight, caused by the plant pathogen Phytophthora infestans. The metamodels used daily or monthly weather data, and their predictions maintained the key features of the original model. This approach can be applied to other complex models, allowing them to be used more widely.
  • Plant pathology in the context of ecosystem services
    Rouse, M. N.; Cheatham, M. R.; Esker, Paul D.; Cardenas, S. I.; Pradel, W.; Raymundo, R.; Sparks, Adam H.; Forbes, Gregory Allan; Gordon, T. R.; Garrett, Karen A. (St. Paul, MN: The American Phytopathological Society, 2007)
    Ecosystem services are processes by which the environment supplies resources that benefit humans. Evaluations of interactions between humans and the environment, such as the Millennium Ecosystem Assessment, are increasingly using the ecosystem services framework. We develop a conceptual model for plant disease within the context of ecosystem services. For example, greater plant biodiversity may provide the service of reducing disease risk in agricultural and natural systems; rice variety mixtures have been successful for managing rice blast. When tillage or the removal of other plant species is motivated by plant disease management, plant disease indirectly results in the reduction of the ecosystem services provided by plants and plant debris, such as regulating soil erosion and provisioning wildlife habitat. Disease may extirpate plant species provisioning food; the loss of chestnut trees due to chestnut blight has reduced the mass produced in Eastern North American forests. Plant pathologists can contribute to evaluation of ecosystem services by clarifying the role of plant disease and to maintenance of ecosystem services by developing disease management methods that optimize for multiple services.
  • Potato late blight in developing countries
    Forbes, Gregory Allan; Grünwald, N. J.; Mizubuti, E. S. G.; Andrade-Piedra, J. L.; Garrett, Karen A. (2007)
    Potato is the fastest growing major crop in the developing world with important economic impact on many resource-poor farming families. Many factors limit production and profitability, with hundreds of millions of dollars spent yearly on fungicides alone, but little is known about direct losses, with experts agreeing that they are variable and frequently significant. Late blight is most severe in the mountainous areas of developing countries where weather conditions are favorable for disease. Variable topography and continuous production of potato and other late blight hosts, including tomato and in the Andes pear melon, make prediction of disease initiation or severity difficult.
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    Regional predictions of potato late blight risk in a GIS incorporating disease resistance profiles, climate change, and risk neighborhoods
    Sparks, Adam H.; Raymundo, R.; Simon, R.; Forbes, Gregory Allan; Garrett, Karen A. (2008)
    This poster prioritizes efforts to manage late blight and measuring their impact now and under future climate scenarios demands a national and global perspective. We used a model in Geographic Information Systems (GIS) to create late blight severity predictions under current and future climate conditions.
  • Regional predictions of potato late blight risk in a GIS incorporating disease resistance profiles, climate change, and risk neighborhoods
    Sparks, Adam H.; Raymundo, R.; Simon, R.; Forbes, Gregory Allan; Garrett, Karen A. (2008)
    This abstract proposes a study to investigate models of forecasting plant pest and disease risk in potatoes due to climate change. The objective is to predict how climate change will affect production across different regions of the world, including Peru and Uganda.