Aromatic Plant Oils as Fungicide for Organic Corn Production

Abstract

The planting date for organic corn (Zea mays L.) is delayed in the spring to avoid cold and wet soils. Conventional farmers can use fungicide seed treatments to protect the emerging seedlings, 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. The essential oils of 18 plants were screened for their fungicidal properties against three common corn pathogens: Penicillium, Fusarium, and Pythium Five oils—cinnamon (Cinnamomum zeylanicum Blume), clove (Eugenia caryophyllata Thunb.), oregano (Origanum minutiflorum O. Schwarz and P.H. Davis), savory (Satureja montana L.), and thyme (Thymus vulgaris L.)—completely controlled all three pathogens in vitro. The minimum inhibitory concentration (MIC) for all pathogens was 800 μL L−1 and seedlings presented no phytotoxicity symptoms in the germination test at rates up to 64 μL kg−1 active ingredient (MIC × 20). Field emergence of inbred and hybrid seeds treated with the essential oils were significantly lower than seeds treated with the commercial fungicides Maxim XL {fludioxonil [4‐(2,2‐difluoro‐1,3‐benzodioxol‐4‐yl)‐1H‐pyrrole‐3‐carbonitrile] 21.4%; mefenoxam [(R)‐2‐[(2,6‐dimethylphenyl) methoxyacetylamino] propionic acid methyl ester] 8.4%}, which is a conventional fungicide; and Natural 2 (proprietary ingredients), which is an organic fungicide, but were not different from the organic fungicide Yield Shield (Bacillus pumilus GB34 0.28%) or an untreated control.