Efeito do óleo essencial de Melaleuca alternifolia no controle de Lasiodiplodia theobromae em sementes de milho.

Abstract

The fungus Lasiodiplodia theobromae causes black rot in maize seeds, leading to significant losses in the production of this cereal. Due to the scarcity of non-harmful natural products that can act in the control of phytopathogens, surveys aiming to find alternative techniques of control and management of plant diseases have increased. This work evaluates the effect of melaleuca essential oil on the mycelial growth of the fungus L. theobromae. We performed in vitro and in vivo experiments. The in vitro experiment was a completely randomized design with six treatments: Melaleuca oil at doses of 0.25, 0.50, 0.75, and 1.0%, one negative control, and one positive control (250 L L−1 of Thiram fungicide). The in vivo experiment tested the effect of essential oil on L. theobromae incidence in corn seeds. The chose of oil concentrations for in vivo tests followed the results of the previous in vitro test and the immediate superior and inferior concentrations. We also compared the efficacy of oil and synthetic fungicide. The concentrations of oil above 0.75% inhibited 100% of L. theobromae growth. The inhibition of mycelia growth increased with concentrations. The oil reduced the fungal incidence on maize seeds but was unable to inhibit 100% the fungal colonies. In general, the oil showed high inhibition on the growth of the studied fungus. Therefore, it is a promising control agent against L. theobromae.