Fungitoxicity of plant extracts and essential oil of Lippia gracilis Schauer on the fungus Monosporascus cannonballus Pollack and Uecker.

Alecrim da Chapada (Lippia gracilis Schauer) is a plant which is considered to be rich in essential oil and proven to have antimicrobial activity due to the phenolic monoterpenes carvacrol and thymol. The aim of this study was to evaluate the in vitro effect of essential oil and ethanol extracts from roots and leaves of L. gracilis on the control of the fungus Monosporasccus cannonballus, the causal agent of melon collapse. The extracts were tested at the concentrations 2500, 5000 and 7500 ppm and L. gracilis essential oil was evaluated at the concentrations 255, 340 and 425 ppm; there was also a positive control with the commercial fungicide Captan(r) and a negative control only with PDA medium (potato, dextrose, agar). Mycelium discs of 3mm diameter were inoculated in the center of Petri plates and measurements of mycelial growth were performed at 48 hours after the establishment of the experiment. L. gracilis essential oil, at the three tested concentrations, was effective in controlling the fungus, showing inhibition percentages of 100%, compared to the treatment with the negative control (0%), which showed no inhibition. The root extract, at concentrations 5000 ppm and 7500 ppm, and the leaf extract, at a concentration of 7500 ppm, also provided inhibition percentage of 100%.