Potencial fungitóxico dos óleos essenciais de copaiba e eucalipto sobre fitopatógenos.

Abstract

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. 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. The experiments comprised completely randomized designs with seven treatments and five replicates. 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). 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, 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. 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.