The antifungal activity of oxine and copper oxinate was investigated using standardized methods to compare efficacy, discriminate
activity patterns, elucidate mechanisms of action and establish attributes of relevance to field use. Both agents were shown to be
active against a broad range of physiologically diverse fungi. Species of Aspergillus, Penicillium, Fusarium, Rhizopus, Candida,
Rhodotorula and Saccharomyces were significantly more resistant than Pythium, Phytophthora, Sclerotina and Trametes, the difference
being greater for oxine than for copper oxinate and in Sabouraud than in Czapek–Dox media. Copper oxinate was generally more
active and more broadly and rapidly fungicidal than oxine. Both are fungicidal at low concentrations against significant plant
pathogens and relatively active against important spoilage and mycotoxin producing moulds. The MIC (minimum inhibitory
concentration) and MFC (minimum fungicidal concentration) for both agents were dependent on method and medium. Neither
agent produced changes in morphology, asexual reproduction or differentiation. Oxine and copper oxinate were resistant to
inactivation by organic materials, interacted synergistically in vitro and did not elicit resistance on long term exposure. Differences in
activity pattern suggest independent modes of action. Oxine is worthy of revisitation as a useful agricultural fungicide and
preservative.