Delaying Infection Through Phytosanitary Soybean-Free Periods Contributes to Fungicide Resistance Management in Phakopsora pachyrhizi: A Modelling Analysis

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Corkley, I., Helps, J., Van Den Bosch, F., Paveley, N. D., Milne, A. E., Mikaberidze, A., Sierotzki, H. and Skirvin, D. J. 2024. Delaying Infection Through Phytosanitary Soybean-Free Periods Contributes to Fungicide Resistance Management in Phakopsora pachyrhizi: A Modelling Analysis. Plant Pathology. pp. 1-19. https://doi.org/10.1111/ppa.14074

AuthorsCorkley, I., Helps, J., Van Den Bosch, F., Paveley, N. D., Milne, A. E., Mikaberidze, A., Sierotzki, H. and Skirvin, D. J.
Abstract

Fungicide resistance threatens control of Asian soybean rust (Phakopsora pachyrhizi) in Brazilian soybean crops: deployment of sound resistance management tactics is crucial to prolong the effective life of new fungicides. A key integrated pest management (IPM) strategy in Brazil is the delay of P. pachyrhizi inoculum influx through soybean-free periods, mandated through restrictions on sowing dates. We developed an epidemiological model of fungicide resistance evolution in P. pachyrhizi to explore the impact of delayed inoculum influx on selection for resistance to a succinate dehydrogenase inhibitor (SDHI) fungicide, and to compare the relative benefits of alternative mixture partners. We fitted model parameters describing the efficacy of fungicides using disease severity data from field trials and validated our approach using a separate dataset from trials of solo and mixture products. Our results suggest that mixture with a multi-site acting fungicide such as mancozeb or chlorothalonil could slow the rate of selection for resistant strains and more than double the number of years for which effective disease control can be maintained. We show how cultural control measures to delay inoculum arrival contribute to resistance management. Delaying infection timing relative to crop emergence reduced selection for fungicide-resistant strains and increased fungicide effective life, through a reduction in the length of time of pathogen exposure to the fungicide and decreased disease pressure. The fungicide resistance management benefits of IPM strategies will be highest in cases where they can keep to a minimum the level of fungicide treatment required to maintain effective disease control.

KeywordsSoybean rust ; Fungicide efficiency; Resistance management; Epidemiological model; Parameterisation; Integrated pest management
Year of Publication2024
JournalPlant Pathology
Journal citationpp. 1-19
Digital Object Identifier (DOI)https://doi.org/10.1111/ppa.14074
Open accessPublished as ‘gold’ (paid) open access
FunderAgriculture and Horticulture Development Board
Biotechnology and Biological Sciences Research Council
Syngenta AG
Funder project or codeGrowing Health (WP3) - bio-inspired solutions for healthier agroecosystems: Discovery landscapes
Output statusPublished
Publication dates
Online04 Mar 2025
Publication process dates
Accepted04 Feb 2025
PublisherWiley
ISSN0032-0862

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