Fungitoxic Potential of Secondary Eucalyptus Metabolites in the Inhibition of Neopestalotiopsis clavispora Isolated From Macadamia

Fungal diseases are responsible for serious injury in forest plantations. The aim of this work was to evaluate the fungitoxic potential of the secondary metabolites in Corymbia citriodora , Eucalyptus camaldulensis and Eucalyptus urophylla leaves for inhibiting the mycelial growth of the Neopestalotiopsis clavispora fungus isolated from macadamia. The essential oils were obtained by the steam drag technique and the aqueous plant extracts by the turbolysis technique, where the yield was determined by the gravimetric method. N. clavispora fungus was cultivated in PDA culture medium with plant extracts at the 18,000, 36,000 and 54,000 ppm dosages and essential oils at the 30, 80, 130 and 180 ppm dosages. The colonies were evaluated after seven days of incubation considering their diameters and the mycelial growth inhibition percentage of the fungus. C. citriodora essential oil provided 100% inhibition at all tested dosages. Essential oils and plant extracts showed better inhibition efficiency when using higher dosages. C. citriodora essential oil was classified as a fungicide in high dosages and fungistatic in low dosages, in addition to the plant extracts of all studied species. Plant extracts provided less inhibition than essential oils. C. citriodora essential oil showed high inhibition efficiency in all tested doses. The presence of citronellal and citronellol compounds in the C. citriodora essential oil were more associated to the fungicidal effect.