Fungicide resistance management: maximising the effective life of plant protection products

Effective crop protection is vital to safeguard food security, but growers are reliant on a limited toolbox in the face of diverse and evolving pathogens. New crop protection methods need to be developed, but it is also important to prolong the effective life of existing products through resistance management.

Some core principles in fungicide resistance management, such as using different modes of action and limiting repeat applications of any single mode of action, are long established. However, other aspects have been long debated, such as using higher or lower dose rates, mixtures or alternations, and whether to spray protectively or only if a disease threshold is reached.

Continuing research into these questions uses a range of approaches, including modelling, experimental trials, and ongoing monitoring of pathogen populations. Molecular diagnostics allow higher-throughput monitoring and earlier detection of emerging resistance. Resistance management guidelines must also be continually updated as new fungicides, and other crop protection measures, are introduced.

Designing optimal resistance management strategies is only half of the story, however, since a strategy will only be effective if growers follow it in practice. This is more difficult where there are hard trade-offs between reducing selection for resistance in the future and achieving greater disease control in the present, or where there is a choice between a strategy that would be optimal on average or one that minimises the risk of control failure in any year. Therefore, communication with farmers is an aspect of resistance management that must not be overlooked.