Modelling Resistance Management Benefits of Incomplete Cross‐Resistance Within a Fungicide Mode of Action Group
6 affiliations
- 1Rothamsted Research Harpenden Hertfordshire UK
- 2ADAS Wolverhampton UK
- 3School of Agriculture, Policy and Development University of Reading Reading Berkshire UK
- 4BU Biointeractions and Plant Health, Wageningen Plant Research Wageningen University and Research Wageningen the Netherlands
- 5NIAB Cambridge UK
- 6Quantitative Biology & Epidemiology Group, Plant Pathology Department University of California, Davis Davis California USA
Abstract
Mixing fungicides with different modes of action (MoA) is a well‐established resistance management tactic which relies on the general absence of cross‐resistance between MoAs. Mixtures of fungicides with the same MoA and complete cross‐resistance are not expected to contribute to resistance management. However, in some cases cross‐resistance is only partial within a MoA, for example azole fungicides in the demethylation inhibitor (DMI) group. We developed and used a mathematical population genetic model to explore possible resistance management benefits of mixtures of fungicides with the same MoA with incomplete cross‐resistance. An important example in agriculture is the deployment of DMIs against the wheat pathogen Zymoseptoria tritici. We modelled selection for known Z. tritici CYP51 haplotypes following application of solo azoles or two, three or four‐way mixtures of epoxiconazole, prothioconazole, prochloraz and tebuconazole. The resulting rate of resistance development was measured as the rate of change in the pathogen population growth rate, ∆r¯: this indicates how fast the level of disease severity will increase as resistance develops. We focused on within‐MoA programmes to investigate resistance management benefits of within‐MoA active substance diversity; in practice azoles should be used in combination with other MoA wherever possible. Our results show that mixtures of fungicides with incomplete cross‐resistance within a MoA can contribute to resistance management, achieving greater stability of disease control. Increasing the number of azole active substances available to mix in various combinations reduced ∆r¯ on average, but with diminishing returns. A generalised linear model fitted to the population genetic model results showed that ∆r¯ increased with the average level of disease control and with the maximum variance in haplotype sensitivity to an individual azole component. Azole combinations with low or negative cross‐resistance maximised resistance management benefits, but any degree of incomplete cross‐resistance was useful.
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BibTeX
@article{corkley2026modelling,
title = {{Modelling Resistance Management Benefits of Incomplete Cross‐Resistance Within a Fungicide Mode of Action Group}},
author = {Isabel Corkley and Neil D. Paveley and Bart A. Fraaije and Joseph Helps and Michael W. Shaw and Alice E. Milne and Nichola J. Hawkins and Frank van den Bosch},
journal = {Evolutionary Applications},
year = {2026},
month = nov,
doi = {10.1111/eva.70346},
url = {https://doi.org/10.1111/eva.70346},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Modelling Resistance Management Benefits of Incomplete Cross‐Resistance Within a Fungicide Mode of Action Group
AU - Isabel Corkley
AU - Neil D. Paveley
AU - Bart A. Fraaije
AU - Joseph Helps
AU - Michael W. Shaw
AU - Alice E. Milne
AU - Nichola J. Hawkins
AU - Frank van den Bosch
PY - 2026
DA - 2026/11/05
JO - Evolutionary Applications
DO - 10.1111/eva.70346
UR - https://doi.org/10.1111/eva.70346
AB - Mixing fungicides with different modes of action (MoA) is a well‐established resistance management tactic which relies on the general absence of cross‐resistance between MoAs. Mixtures of fungicides with the same MoA and complete cross‐resistance are not expected to contribute to resistance management. However, in some cases cross‐resistance is only partial within a MoA, for example azole fungicides in the demethylation inhibitor (DMI) group. We developed and used a mathematical population genetic model to explore possible resistance management benefits of mixtures of fungicides with the same MoA with incomplete cross‐resistance. An important example in agriculture is the deployment of DMIs against the wheat pathogen Zymoseptoria tritici. We modelled selection for known Z. tritici CYP51 haplotypes following application of solo azoles or two, three or four‐way mixtures of epoxiconazole, prothioconazole, prochloraz and tebuconazole. The resulting rate of resistance development was measured as the rate of change in the pathogen population growth rate, ∆r¯: this indicates how fast the level of disease severity will increase as resistance develops. We focused on within‐MoA programmes to investigate resistance management benefits of within‐MoA active substance diversity; in practice azoles should be used in combination with other MoA wherever possible. Our results show that mixtures of fungicides with incomplete cross‐resistance within a MoA can contribute to resistance management, achieving greater stability of disease control. Increasing the number of azole active substances available to mix in various combinations reduced ∆r¯ on average, but with diminishing returns. A generalised linear model fitted to the population genetic model results showed that ∆r¯ increased with the average level of disease control and with the maximum variance in haplotype sensitivity to an individual azole component. Azole combinations with low or negative cross‐resistance maximised resistance management benefits, but any degree of incomplete cross‐resistance was useful.
SN - 1752-4571
ER -