Co-encapsulação bioativo/feromônio em nanocompósito polímero/silicato lamelar

Abstract

The coconut (Cocus nucifera L.) culture deserves a special mention in the national scenario, mainly because of its economic, social and environmental importance. Infestations by borer-eye-of-coconut (Rhynchophorus palmarum) cause great damage to the agrosystems that cultivate this palmácea. There is a great lack of products used in its control, being the synthetic aggregation pheromone, Rhynchophorol, the only registered product for such. The use of entomopathogenic agents, such as the fungus Beauveria bassiana, has been shown to be promising in Integrated Pest Management (IPM). Its encapsulation in Polymer-layered Silicate Nanocomposite (PLN) provides bioactive protection to deleterious factors, ensures greater adhesion and permanence of the product at the site of action and greater effectiveness in the population control of the pest. Thus, the present work aimed to develop and evaluate a co-encapsulated nanocomposite containing the bioactive in association with Rhynchophorol. Beads were formed by the ionotropic gelation technique followed by lyophilization drying, and different concentrations of lamellar silicate were tested. The products were evaluated by X-ray diffractometry, infrared spectroscopy, yield, swelling index, morphology, Rhynchophorol quantification and conidia release study. Direct exposure to Rhynchophorol demonstrated a deleterious effect on viability, with delay or even non-viability of conidia. However, protective effect was achieved by encapsulating these in the polymer matrix / lamellar silicate, especially for the highest concentration of clay tested, 6%. DRX and FTIR were essential in elucidating the interactions between the components of the matrix. Bentonite provides the improved yield of the formulations. In addition, it acts as a structural reinforcement of the polymer network, generating beads with greater degree of spherization and decreasing the water uptake by delaying the relaxation of the polymer network, an essential phenomenon in obtaining control of the release of the assets. The efficiency of encapsulation of the pheromone and of the bioinsecticide increased proportionally to the higher content of incorporated silicate, as well as there was modulation of the volatilization of Rhynchophorol. The distribution of the bioactive in the matrix, observed by fluorescence microscopy, was homogeneous, characterizing a monolithic profile. Cryoprotection against the deleterious effects of freezing applied on lyophilization was achieved in product F6, corroborating with the protective effect seen in pheromone exposure. In this way, the encapsulation matrix demonstrates great potential for co-encapsulation of bioactives and production of effective pheromone releasing devices.