ATIVIDADE LARVICIDA FRENTE À Aedes aegypti DE Bacillus thuringiensis israelensis e ÓLEO ESSENCIAL DE Croton rhamnifolioides MICROENCAPSULADO

Abstract

Aedes aegypti is the main mosquito transmitting diseases such as dengue, zika, chikungunya and yellow fever to humans. Methods of control involve awareness of the elimination of mosquito breeding foci, application and use of insecticides and repellents as individual and collective protection. Prolonged use of chemical pesticides has been reducing its potential effect due to the resistance created by mosquitoes against such products. To minimize these adverse effects, the use of natural and biological products has been constant because they present larvicidal characteristics with high potential in the fight against the propagation of diseases. However, the use of natural products such as essential oils and biolarvicides such as Bacillus thuringiensis israelensis (Bti) have limitations resulting from low solubility in water, high volatility and degradation when exposed to light. To minimize such problems, microencapsulation techniques are adopted to act as a protection, avoiding the effect of inadequate exposure of the active substance. This work aims to evaluate the larvicidal activity of Bacillus thuringiensis israelensis microencapsulated with essential oil of Croton rhamnifolioides. Bti dry powder was obtained by culturing the active strain in erlenmeyer flasks containing New Brunswick Scientific shaker table culture medium. The Bti microspheres, Croton rhamnifolioides essential oil and Bti + oil were obtained by the simple coacervation method by dripping the suspensions in 2% and 1% sodium alginate in CaCl2 medium which is responsible for the ion exchange and the formation of the microspheres. The larvicidal tests of the microspheres were performed in triplicate and in parallel with the activity test of the fermented powder of Bti. The assays were performed using 20 larvae per test, in flasks containing 100 ml of distilled water and 0.1 g of the microspheres for testing. The CL 50 and CL 90 obtained from the dry powder were, respectively, 0.12 mg / L and 0.21 mg / L, and maintained the activity after one year of storage period at -10 ° C. Bti, Bti + Croton rhamnifolioides oil microspheres and Croton rhamnifolioides oil microspheres in 2% alginate showed no mortality, while microspheres in 1% alginate showed 90% mortality in 3x104 CFU / g Bti immobilized. The results obtained showed viability for the use of Bti microspheres associated with Croton rahminifolioides essential oil for the control of Aedes Aegypti. Process optimization conditions still need to be established