In vitro Fungitoxic Potential of Copaiba and Eucalyptus Essential Oils on Phytopathogens

Aims: This study evaluates the in vitro fungitoxic effect of copaiba (Copaifera sp.) and eucalyptus (Eucalyptus sp.) essential oils on the mycelial growth of Alternaria alternata and Colletotrichum musae.

Study Design: The experiments comprised completely randomized designs with seven treatments and five replicates.

Place and Duration of Study: The work was carried out at the Center for Agrifood Science and Technology of the Federal University of Campina Grande, Pombal, Brazil, from July to August 2018.

Methodology: Essential oils were incorporated into PDA culture medium (Potato-Dextrose-Agar) and poured into Petri dishes. The treatments consisted of four oil concentrations (0.4, 0.6, 0.8, and 1.0%), a negative control (0.0%) and two positive controls (the fungicides Thiram and Mancozeb). The fungi were inoculated on plates and incubated for seven days at 27±2°C. The diameter of the colonies was measured every day and use to calculate the percentage of mycelial growth inhibition (PGI) and index of mycelial growth speed (IMGS).

Results: Copaiba and eucalyptus oils reduced the mycelial growth of A. alternata and C. musae in all concentrations. The copaiba oil showed a moderate inhibition, with mean percentages ranging from 26.6 to 33.68% for A. alternata and 39.5 to 49.6% for C. musae. The eucalyptus oil showed high inhibition, with means ranging from 30.0 to 79.7% for A. alternata and 35.6 to 66.3% for C. musae. The concentrations 0.8 and 1.0% had the highest inhibition values in both oils treatments, but these inhibitions were lower than the ones caused by the fungicides. The eucalyptus oil at 1.31% could totally inhibit A. alternata, but in all other cases, the oils were unable to cause total inhibition.

Conclusion: Copaiba and eucalyptus oils inhibit the mycelial growth of A. alternata and C. musae under in vitro conditions. Concentrations of 0.8 and 1.0% provided the highest inhibitory effect.