Ação do óleo essencial de menta (Mentha arvensis) sobre o patógeno Lasiodiplodia theobromae em cachos de videira cv. Itália

Abstract

The presence of Lasiodiplodia theobromae (dry rot) on the vine, in irrigated areas of the Brazilian semi-arid region, has been very aggressive, infecting several plant parts. Essential oils show efficient disease control, both for their fungitoxic action, which inhibits mycelial growth and spore germination, and for the presence of elicitor compounds. Thus, this study aimed to obtain L. theobromae control by using the oil from mint (Mentha arvensis). The mycelial growth of L. theobromae was analyzed on Petri plates containing potatodextrose-agar medium supplemented with the essential oil at the following concentrations: 0; 0.25; 0.5; 1.0; 1.5; 2.0% of mint oil. To evaluate the direct effect of the essential oil on the disease development, the grape bunches were inoculated with the pathogen and, after 4 h, sprayed with solutions containing the same previously described concentrations; then, to evaluate the potential of essential oil in the preventive treatment, the same treatments were applied on grape bunches at 4 hours before inoculation. The mint oil, at all tested concentrations, was capable of inhibiting the mycelial growth of L. theobromae by 100%. In the curative treatment, considering incidence, 0.25% mint was statistically different from the remaining treatments, showing 88% infected berries, while dry rot severity of grape bunches could not be reduced by any of the concentrations. For the preventive treatment, considering incidence, 0.5% mint oil statistically differed from control, showing 86% and 94% infected berries, respectively, and there was greater reduction in dry rot severity, since the disease index was 73.7%, compared to control, which had disease index of 98%.