Plant extracted essential oils as a contact fungicide seed treatment for organic corn

Abstract

Planting date for organic corn (Zea mays L.) is delayed to avoid the cold and wet soils of spring. Conventional farmers can use fungicide seed treatments to protect the emerging seedling but few organic fungicides are available. The objective of this research was to determine whether essential oils can be used as a contact fungicide seed treatment for organic corn. Eighteen plant essential oils were screened for their fungicide properties against three common corn pathogens Penicillium, Fusarium, and Pythium. Five oils completely controlled all three pathogens in vitro. These oils were cinnamon, clove, oregano, savory, and thyme. The minimum inhibitory concentration (MIC) for all pathogens was 800 μL L and there was no phytotoxicity seen in the germination test at rates up to 16 000 μL L (MIC × 20). Field emergence of inbred and hybrid seeds treated with the essential oil were significantly lower than seed treated with the commercial fungicides Maxim XL, which is a conventional fungicide, and Natural 2, which is an organic fungicide, but not different from an organic fungicide Yield Shield or an untreated control.