In this study, microencapsulation by spray drying was performed to protect spores and crystals of indigenous isolate of Bacillus thuringiensis Se13 from environmental stress. The effects of wall material, inlet temperature, and outlet temperature on microencapsulation of Bt-Se13 were investigated using Taguchi’s orthogonal array. The most suitable wall material determined as maltodextrin DE10. The optimum inlet and outlet temperatures of spray drier were determined as 160 °C and 70 °C, respectively. The number of viable spores, mean particle size, wetting time, percentage of suspensibility and moisture content of the product produced under optimum conditions were determined as 8.1 × 10¹¹ cfu g⁻¹, 13.462 µm, 25.22 second, 77.66% and 7.29%, respectively. As a result of efficiency studies on S. exigua in the laboratory conditions, the LC₅₀ was determined as 1.6 × 10⁴ cfu ml⁻¹. Microencapsulated Bt-Se13 based bio-pesticide may be registered for the control of S. exigua and can be tested against other lepidopterans which share the same environment.

Microorganisms and their metabolites have the potential to provide a sustainable alternative to chemical insecticides. Serratia marcescens is an entomopathogenic bacterium that produces hydrolytic enzymes and toxins. It also produces a red pigment called prodigiosin, which has a variety of biological properties. In this study, the prodigiosin pigment was extracted from S. marcescens Se9 isolate with acidified ethanol and concentrated using a rotary evaporator. The insecticidal potential on larval and adult stages of Tenebrio molitor was then investigated. It was found that the mortality rate of larvae exposed to the lowest concentration (125 ppm) of crude pigment was 5%, while the mortality rate of larvae exposed to the highest concentration (2000 ppm) was 68%. The LC50 value of the crude pigment for the larval stage was determined to be 924 ppm. On the other hand, even at the highest pigment concentration (2000 ppm), only 30% mortality was observed in adults. The LC50 value of the crude pigment for the adult stage was determined to be 4570 ppm. It was determined that the pigment had a toxic effect on the pest, but the larval stage was more sensitive than the adult stage. The study showed that prodigiosin pigment appears to be a promising biocontrol agent for use against T. molitor.