Fumigant Antifungal Activity of Corymbia citriodora and Cymbopogon nardus Essential Oils and Citronellal against Three Fungal Species

Corymbia citriodora and Cymbopogon nardus essential oils samples were analyzed by GC and GC-MS and their qualitative and quantitative compositions established. The main component of essential oils of C. citriodora and C. nardus was citronellal, at 61.78% and 36.6%, respectively. The essential oils and citronellal were tested for their fumigant antifungal activity against Pyricularia (Magnaporthe) grisea, Aspergillus spp., and Colletotrichum musae. The minimum inhibitory concentration (MIC) ranged from 100 to 200 ppm for the essential oils and 25 to 50 mg·mL(−1) for citronellal. The contact assay using the essential oils and citronellal showed growth inhibition of the three fungal species. However, a concentration of 1.47 mg·mL(−1) only reduced the inhibition of Aspergillus growth to 90% at 14 days of exposure. For the fumigant assay, 0.05, 0.11, and 0.23 mg·mL(−1) of essential oils and citronellal drastically affected growth of P. grisea, Aspergillus spp., and C. musae. Harmful effects on the sporulation and germination of the three fungi were seen, and there was complete inhibition at 0.15 mg·mL(−1) with both oils and citronellal. This showed that the crude component of essential oils of C. citriodora and C. nardus markedly suppressed spore production, germination, and growth inhibition of P. grisea, Aspergillus spp., and Colletotrichum musae.