Enhancing the effectiveness and stability of biopesticides Bacillus thuringiensis against Spodoptera frugiperda J.E Smith (Lepidoptera: Noctuidae) by lyophilization freeze-drying

Abstract

The Gram-positive spore-forming bacterium Bacillus thuringiensis (Bt) Berliner produces crystal proteins as its main characteristic. The agricultural industry uses this bacteria because its insecticidal proteins established it as an effective environment-friendly biopesticide.  The investigation into using freeze drying to produce the biopesticides Bacillus thurigiensis as a powder for control Spodoptera frugiperda damage on maize in Vietnam. This study assessed the stability of this product as pure biopesticides on Spodoptera frugiperda during storage. The results showed that the viability of the formulated B. thuringiensis spore-crystal complex stored at 4°C and 25°C was maintained at 22.9 × 1022 and 19.5 × 1022 CFU/g, respectively, after one month of drying storage. Furthermore, freeze-drying supported the viability of the B. thuringiensis spore-crystal complex for up to 18 months, with 10.2 × 1022 CFU/g and 1.01 x 1022 CFU/g in both temperature conditions during storage, respectively. Our study demonstrated the potential of the freeze-dried Bacillus thuringiensis spore-crystal complex powder as a more effective biopesticide. The efficiency against Spodoptera frugiperda second instar larvae showed that after 12 months during storage at two conditions, 4°C and 25°C, the B. thuringiensis spore-crystal complex powder killed 94.7% and 88% in the highest concentration of 35 mg/L. This suggests that the B. thuringiensis spore-crystal complex powder, when formulated by the freeze-drying method, could significantly improve its activity as a biopesticide under laboratory and net-house conditions. This promising result offers a bright future for pest control, with the potential for more effective and stable biopesticides.