Avaliação da eficácia do óleo essencial de Melaleuca encapsulado em pectina cítrica no controle in vitro de Leucoagaricus gongylophorus

Abstract

Leaf-cutting ants of the genera Atta and Acromyrmex are widely found in Brazil. These social insects collect plant material to use as a substrate for the symbiotic cultivation of the fungus Leucoagaricus gongylophorus, with which they maintain a mutualistic relationship. However, this foraging activity causes damage to human activities related to forestry, grazing, and agriculture. The control of these ants is generally carried out using chemical agents, which may have harmful effects on the environment and human health. An alternative approach involves the use of plant secondary metabolites to control these populations. However, such compounds are often unstable and difficult to control in terms of release. To address these issues, an encapsulation process using biopolymers has been explored. The main objective of this study was to develop a formulation aimed at controlling leaf-cutting ants. The approach was based on the use of essential oil from Melaleuca alternifolia, also known as tea tree. This essential oil is widely used in hygiene products and as a herbal remedy for skin conditions, among other uses, and has proven effectiveness in microbial control. The first part of the study consisted of biological assays to evaluate the activity of the essential oil on the growth of the symbiotic fungus at various concentrations. Complete inhibition was observed at concentrations above 15 microliters. Based on a literature review on biopolymers, citrus pectin was selected as the encapsulating agent. To develop the formulation method, several experiments were conducted with variations in process parameters, aiming to maximize encapsulation yield. This yield was quantified using gas chromatography coupled with mass spectrometry, employing the headspace technique. A formulation with approximately 84% yield was obtained. Using this formulation, a biological assay was carried out to evaluate its effect on the growth of L. gongylophorus, resulting in 80% fungal growth inhibition. These results indicate that the developed formulation may serve as an ecological and effective alternative to conventional compounds for the control of leaf-cutting ants.