While farmers typically spray fungicide to manage one disease, applications should be considered in a broader context. Dr Steven Simpfendorfer describes how spraying one pathogen can inadvertently encourage resistance in other pathogens that may be present. He outlines some typical examples, including rusts and powdery mildew in wheat; blackleg and sclerotinia in canola; as well as net blotches and powdery mildew in barley.

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