In addition, the antifungal effect of each treatment on white rot progress was evaluated by calculating area below the disease progress curve (ABDPC) (Table 5). Significant differences were found in ABDPC for all treatments (p < 0.05). The highest values observed were for the control and Ip samples. The combinations Ip with An (0.6 μL/L + 900 μL/L) and Ip with Ba (0.6 μL/L + 900 μL/L) had the lowest ABDPC values, being significantly different to the rest of the samples. All other treatments showed intermediate ABDPC values. Our results are in accordance with those observed by Zewide et al. (2007), who reported lower ABCDPC and sclerotia density in garlic crops treated when a synthetic fungicide was applied to the soil.
4. Conclusion
The management of plant diseases with natural compounds is highly needed nowadays. The results of this study evidence that the antifungal power of non-phytotoxic EOs can be used to reduce doses of synthetic compounds that are applied to garlic crop. Anisillo and bay EOs have both moderate antifungal activity but no phytotoxic effect. Moreover, some combinations of these EOs with Ip can reduce the fungicide dose by up to 40% due to the synergistic interactions taking place. Therefore, these EOs are a novel alternative to control “white rot” caused by S. cepivorum and can be applied with Ip not only to reduce the amount of chemical fungicide in the soil, but also to reduce the disease incidence and the sclerotia density after white rot disease. Moreover, the persistence of fungicides and the amount of money spent on them can be reduced. Future studies are needed to adjust the applied concentrations.
Acknowledgments
We thank the National University of Cordoba, Secretary of Science and Technology (UNC, SECyT) and Argentinian National Research Council (CONICET) for the financial support.