Monitoring fungicide resistance frequencies - a case study of barley net blotch

Decreased sensitivity to fungicides impacts the effectiveness of fungicide applications for managing plant disease, in some cases resulting in field-level failures. Knowledge of the frequency of decreased sensitivity in field populations is critical for evaluating risks for disease control. This study applied a droplet digital PCR detection approach to assess pathogen populations and quantify the frequencies of alleles associated with decreased sensitivity to either demethylation inhibitor (DMI) or succinate dehydrogenase inhibitor (SDHI) fungicides in Pyrenophora teres causing net blotch on barley in Western Australia.

Pyrenophora teres f. maculata was the most frequent form of the pathogen in the sampled region. Frequencies of decreased fungicide sensitivity alleles varied, being as great as 92% for the PtTi insertion in the Cyp51A promoter, 88% for SdhC-S75, and 28% for Cyp51A L489-2. Impacts of cultivar selection and weed hosts on the presence and survival of pathogen populations with decreased fungicide sensitivity were observed.

Determining the dynamics of alleles within different field populations of P. teres provides an important perspective on the impact of fungicides, the fitness associated with decreased fungicide sensitivity alleles, and the susceptibility of barley cultivars. These findings support the need for ongoing surveillance and integrated management strategies to mitigate the impact of decreased fungicide sensitivity and sustain effective net blotch control. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.