Brevicoryne-Kill: A Novel Eco-Friendly Biopesticide Based on Bacillus thuringiensis against Brevicoryne brassicae (L.) (Hemiptera: Aphididae)

Abstract— Bacillus thuringiensis (Bt) is a widely used entomopathogenic bacterium in the biological control of agricultural pests. This study collected soil samples from seven cities in Türkiye between February and August 2024 to isolate native Bt strains. Based on 16S rRNA gene sequencing, nine isolates were identified as B. thuringiensis with 99–100% similarity. Phylogenetic analysis showed that the Turkish isolates mostly clustered together. During the same period, high population densities of Brevicoryne brassicae were observed in cabbage fields, causing significant crop damage. The study aimed to evaluate the insecticidal potential of the isolated Bt strains against B. brassicae. Adults were collected and reared in the laboratory. After two generations, Bt isolates were applied to cabbage leaves infested with winged adults at five concentrations (1 × 104 to 1 × 108 spore-crystals/mL). After 7 days, 100% mortality was observed at the highest concentration for isolates Bt-2, Bt-5, Bt-10, Bt-11, and Bt-28. Among them, Bt-5 caused the highest mortality even at the lowest dose (1 × 104 spore crystals/mL), reaching 70% by the 7th day. Bt-5 was then formulated into a product named Brevicoryne-Kill and tested in the field alongside a commercial Bt product and a control formulation. After 7 days under field conditions, Brevicoryne-Kill achieved the highest mortality rate at 70%. This represents the first field evaluation of a formulated microbial control agent against B. brassicae and highlights the strong potential of Bt-5 as a bioinsecticide candidate for further development.