Optimization of Mexican Oregano Essential Oil (Lippia Graveolens) Extraction with Fungicidal and Oomyceticidal Effects Against Plant Pathogens

Botanical extracts are being considered for integration into disease management programs to control plant pathogenic fungi and oomycetes. A promising extract with potential is the essential oil of Lippia graveolens. However, its extraction process has not been optimized. Since optimizing process conditions can impact fungicidal and/or oomyceticidal effects, this research implemented time, temperature, and solid/liquid ratio conditions to maximize the fungicidal and oomyceticidal effects. The effectiveness was evaluated through parameters of mycelial growth inhibition, spore germination inhibition, minimum inhibitory and fungicidal/oomyceticidal concentration for the fungi Gilbertella persicaria, Agroathelia rolfsii, and Colletotrichum gloeosporioides, as well as the oomycete Phytophthora capsici. Optimal conditions were as follows: time: 46.27 min; temperature: 329.34 °C; and solid/liquid ratio: 80.35 g/L. In general, the optimized treatment was more effective in A. rolfsii ≥ P. capsica > G. persicaria ≥ C. gloeosporioides in all assays. These results demonstrate the fungicidal and oomiceticidal effects of L. graveolens essential oil, with potential for commercial product formulation.