Chemical composition and control of Sclerotium rolfsii Sacc by essential oils

Abstract

Essential oils of medicinal plants show potential to control phytopathogens. Essential oils of Lippia sidoides Cham, Lippia lasiocalycina Cham, Lippia origanoides Kunth -Teresina, Lippia origanoides Kunth -Jatobá, Mesosphaerum suaveolens (L.) Kuntze, Croton sonderianus Muell. Arg. And Croton zehntneri Pax et Hoffm. were evaluated regarding their chemical composition and in controlling the Sclerotium rolfsii Sacc. The experiments were carried out in a completely randomized design with five concentrations and the control (without oil application): 0.0313; 0.0625; 0.1250; 0.2500 and 0.500 mL kg -1 in Petri dishes with PDA medium (potato-dextrose-agar). The evaluations consisted of daily measurements of the colony diameter in diametrically opposite directions, 24 h after the experiment installation and maintained until the radial reach of the colony on the edges of the Petri dish, in one of the treatments. The chemical composition of the essential oils were evaluated by GC-MS and the following compounds were identified: Thymol (33.5%, L. sidoides); piperitenone oxide (67.7%, L. lasiocalicyna); borneol (19.2%, L. origanoides); borneol carvacrol (34.4%, L. origanoides -Jatobá); sabiene (30.3%, M. suaveolens); β-sabinene (30.5%, C. sonderianus); and estragole (90,1%, C. zehntneri). The S. rolfsii fungus is highly sensitive to L. sidoides, L. origanoides -Jatobá and C. zehntneri essential oils, suggesting its use in the management of Sclerotium wilt in cowpea.