Abstract
The fungus Beauveria bassiana is widely used for pest control; however, biostability and dispersion for broth pulverization are limiting factors for its application in the field. In this context, formulation techniques such as microencapsulation are viable alternatives. The aim of this work is to optimize B. bassiana formulations by spray dryer and evaluate its stability and biological activity against Spodoptera cosmioides compared to ionic gelatinization formulations. The fungus was biocompatible with all evaluated biopolymers (lignin, cellulose, starch, humic substances, and alginate). The encapsulation by spray drying was optimized by factorial design in an inlet and outlet air temperature of 120°C and 68°C, respectively; aspirator rate of 35 m3·h−1, feed flow rate of 12 mL·min−1; and drying gas flow at 35 L·h−1. The ionic gelation capsules were obtained using a 0.5% quantity of conidia in a 1% sodium alginate solution dropped into a 0.5 mol·L−1 CaCl2 solution using a peristaltic pump. Spray drying provided smaller microcapsules than those by ionic gelation. Both techniques produced more stable conidia when exposed to temperature and UV-radiation than non-formulated B. bassiana. The formulations prepared by spray drying showed gains at aqueous dispersion. Biological assays against Spodoptera cosmioides showed a mortality rate of up to 90%. These results demonstrate the suitability of encapsulating B. bassiana conidia stably in aqueous dispersion without loss of viability and virulence.
Highlights
The control of agricultural pests has been conducted mainly by synthetic chemical insecticides
Biocompatibility Assays Between the Biopolymers and B. bassiana The assay allowed the calculation of the Biological Index (Gonçalves Diniz et al, 2020), assigning different levels to fungal development stages, quantified by the impacts of encapsulating agents to the microbial growth medium
The results indicated that B. bassiana was resistant to the encapsulating agents in almost all evaluated concentrations, suffering little or no influence during its life cycle
Summary
The control of agricultural pests has been conducted mainly by synthetic chemical insecticides. This control system has been efficient in promoting productivity gains every year. It is responsible for several harmful damages to the environment (Sharma et al, 2019). Prolonged exposure to conventional synthetic pesticides raises occupational risks, disturbances to human health, and harmful impacts on ecosystems and the environment. These substances may attack non-target species and/or lead to the emergence of new pests (Keshani et al, 2015). Several studies highlight the negative effects of synthetic pesticide use on human health (Heckel, 2012; Asghar and Malik, 2016; Bourguet and Guillemaud, 2016; Op de Beeck et al, 2017; Sharma et al, 2019)
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