Using epidemiological principles to explain fungicide resistance management tactics: why do mixtures outperform alternations?

A - Papers appearing in refereed journals

Elderfield, J. A. D., Lopez-Ruiz, F. J., Van Den Bosch, F. and Cunniffe, N. J. 2018. Using epidemiological principles to explain fungicide resistance management tactics: why do mixtures outperform alternations? Phytopathology. 108 (7), pp. 803-817.

AuthorsElderfield, J. A. D., Lopez-Ruiz, F. J., Van Den Bosch, F. and Cunniffe, N. J.
Abstract

Whether fungicide resistance management is optimized by spraying chemicals with different modes of action as a mixture (i.e., simultaneously) or in alternation (i.e., sequentially) has been studied by experimenters and modelers for decades. However, results have been inconclusive. We use previously parameterized and validated mathematical models of wheat Septoria leaf blotch and grapevine powdery mildew to test which tactic provides better resistance management, using the total yield before resistance causes disease control to become economically ineffective (?lifetime yield?) to measure effectiveness. We focus on tactics involving the combination of a low-risk and a high-risk fungicide, and the case in which resistance to the high-risk chemical is complete (i.e., in which there is no partial resistance). Lifetime yield is then optimized by spraying as much low-risk fungicide as is permitted, combined with slightly more high-risk fungicide than needed for acceptable initial disease control, applying these fungicides as a mixture. That mixture rather than alternation gives better performance is invariant to model parameterization and structure, as well as the pathosystem in question. However, if comparison focuses on other metrics, e.g., lifetime yield at full label dose, either mixture or alternation can be optimal. Our work shows how epidemiological principles can explain the evolution of fungicide resistance, and also highlights a theoretical framework to address the question of whether mixture or alternation provides better resistance management. It also demonstrates that precisely how spray tactics are compared must be given careful consideration. Copyright ? 2018 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Year of Publication2018
JournalPhytopathology
Journal citation108 (7), pp. 803-817
Digital Object Identifier (DOI)doi:10.1094/PHYTO-08-17-0277-R
Open accessPublished as ‘gold’ (paid) open access
Publisher's version
Output statusPublished
Publication dates
Online22 May 2018
Publication process dates
Accepted25 Jan 2018
ISSN0031949X
Copyright licenseCC BY

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