Modelling the Control of Fungal Crop Disease: Challenging traditional assumptions

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• Matthew Castle
• Friday 04 June 2010, 13:00-13:30
• Department of Plant Sciences, Large Lecture Theatre.

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Fungal crop diseases continue to have a huge impact on agricultural practices globally. With both resurgence in fungicidal resistance by traditional pathogen strains (Phytophthora infestans on Solanum tuberosum) and the introduction of non-native pathogen strains to new host areas (Phytophthora ramorum on Quercus spp.) the need for well considered control strategies has never been higher. Epidemiological modelling has long been an integral part of a comprehensive control strategy, however the modelling of chemical control usage has historically been greatly simplified and the consequences of this simplification have not been thoroughly investigated or justified.

We reconsider the assumptions underpinning widely used models for fungicide behaviour at plant, field and landscape scales. We show that many of these models are based on assumptions that take into account the dynamics of the pathogen but fail to take into account the dynamics of the fungicide and so give erroneous predictions of the fungicides efficacy. Accordingly we develop models that incorporate more detailed fungicide dynamics and using selected examples show how these change predictions.

In one such example, we give a description of a novel, leaf-scale model for fungal lesion growth. Here we propose that the physical leaf geometry (its size and shape) is an important factor in characterising spore production for certain pathogens. Consequently, the epidemiological concept known as “force of infection” (approximately a measure of the rate with which infectious hosts infect uninfected hosts), can be related directly to the mechanistic leaf-scale processes of fungal lesion growth. We show that by modelling fungicides at these scales, conventional assumptions regarding their effects (via their effects on larger scale infection parameters, such as force of infection) can lead to misleading conclusions about the fungicide’s wider impact.

This talk is part of the Plant Sciences Research Seminars series.

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