Avaliação de nanocompósito polimérico como matriz para formulações bioinseticidas

Abstract

The importance of the culture of coconut (Cocus nucifera L) is noteworthy for several factors, including: economic, social and environmental. The incidence of infestations of the borer-eye-of-coconut Rhynchophorus palmarum L. (Coleoptera: Curculionidae), affect agroecosystems that cultivate this palmacea. The only product used in Brazil to control this pest is the synthetic aggregation pheromone, Rincoforol. A recent strategy that has been successfully used is the use of agents such as entomopathogenic fungus Beauveria bassiana. The encapsulation of the biopesticide in polymer matrices can protect fungal material deleterious factors, and can ensure greater adherence of the product in the insect and/or coconut palm, providing greater efficiency and increased stability in the application so it can be stored for a long period. Thus, the aim of this study was to evaluate a polymer nanocomposite as the matrix for this biopesticide. Beads were formed by ionotropic gelation techniques, with different tested conidia and layered silicate concentrations. The matrix was evaluated by X-ray diffraction and infrared spectroscopy; Products were evaluated for yield, encapsulation efficiency, distribution of conidia on the beads, swelling index, size distribution and polydispersity, morphology, in vitro release studies, stability and production cost. The results show that this matrix is capable of encapsulating large amounts of spores, without interfering with the process of germination. XRD analysis showed no intercalation, but the interactions between the compounds were elucidated by FTIR. Conidia in the matrix were visualized by fluorescence techniques. It was found that clay addition resulting improved performance as well as higher encapsulation efficiency, while reducing the swelling index of the beads. Furthermore, all products were homogeneous in size, a result of the narrow range of polydispersity and increasing concentration of bentonite appeared to be accompanied by a spherize of beads. Higher concentrations of the clay mineral (4 and 6%) have provided the fungus modified release profiles, both having retardation of germination and early in its development. The product of the highest concentration of bentonite evaluated for 10 months (AB4) remained stable, with normal germination mycelia, over the entire period when refrigerated, or when for 5 months at room temperature.