Organic Oils as Seed Treatments for Soybeans to Inhibit Fungal Growth

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Virginia Tech


Producing organic crops has become essential to satisfy the desires of the end consumer. To completely fulfill this task and meet the requirements of the National Organic Program in the U.S., the seeds planted must be organic. Seeds succumb to fungal infections without seed treatments. Organic seed treatments are not common. The purpose of this study is to test the ability of three organic oils (tea tree, coconut, and lemon) to act as organic seed treatments to inhibit fungal growth on soybean seeds that were badly infected with fungal disease. Each oil treatment was tested with three separate concentrations 10%, 50%, and 100%. The treatments were observed for 10 days and the results were recorded as a percentage of seeds infected with fungi. Both lemon oil and coconut oil at all concentrations failed to inhibit fungal growth. Tea tree oil at all three concentrations successfully prevented fungal infection on 100% of the seeds. The effective treatments show promise as organic seed treatments. Because of the positive results from the tea tree oil, it was further tested for germination and fungal inhibition on live soybean seeds at 2%, 5% and 10% concentrations. The treatments were observed for 12 days, and the results were recorded as a percentage of seeds infected with fungi. The germination rate and final germination percentage were also recorded. The 10% concentration inhibited a high percentage of fungi, but inhibited germination completely. The 2% and 5% concentrations had low germination percentages and mediocre fungal inhibition. The results from this research project show that there are still many options to explore in terms of organic seed treatments. Tea tree oil should be further tested in field studies, viability and vigor tests, and the germination study should be replicated at the 2% and 5% concentrations. Tea tree oil is effective against certain seed fungal contaminants, but also displays some phytotoxicity at low concentrations. Research should be completed to find tea tree oil’s effect on seedling emergence and early seedling growth. Tea tree oil could be effective in conjugation with other organic seeds treatments. Other essential oils that are produced organically should be tested against fungal control, and tea tree oil should be thoroughly tested and considered for cost effectiveness and possible health effects to farm workers.