Effect of essential oils on in vitro control of Lasiodiplodia theobromae

The postharvest rots due to the fungus Lasiodiplodia theobromae are responsible for much of the loss of stored fruit, especially the mango and papaya. The objective of this study was to evaluate the effect of different concentrations of essential oils of Lippia sidoides and Lippia gracilis on the growth of fungus L. theobromae. We used concentrations of 0.1, 0.3, 0.5, 0.7 mu L mL(-1) of essential oils. The essential oil was added to the PDA, and then poured into Petri dishes. Each plate was inoculated with a mycelial disc of the pathogen. The evaluations were performed daily by measuring the diameter of the colonies. The chemical components of the oils were identified by comparison of mass spectra and comparison of the retention indices. After four days of incubation at 25 degrees C and a photoperiod of 12 h assessment was made by measuring the diameters of colonies and percentage inhibition compared to control. The results showed that except for the concentration of 0.1 mu L mL(-1) of essential oil of L. sidoides, which inhibited 84% of mycelial growth, the remaining concentrations of both oils inhibited 100% of mycelial growth of L. theobromae. The inhibition caused by essential oils L. sidoides and L. gracilis is probably due to the high content of thymol (42.33 and 18%) and carvacrol (4.56 and 27.59%), respectively. These results demonstrate the possibility of using the essential oils of L. sidoides as a tool for postharvest treatment.