Aims The leaf‐feeding pest Cerotoma arcuata tingomariana (Bechyné) (Coleoptera: Chrysomelidae) produces huge economic losses in different crops. This study aimed to produce conidia by semisolid‐state fermentation and to establish the insecticidal activity of two formulation prototypes based on a native Beauveria bassiana isolate for controlling this pest. Methods and results A novel fabric‐based semisolid‐state fermentation strategy for quick and large‐scale conidia production was performed and characterized. Conidia were formulated as an emulsifiable concentrate (EC) and a water‐dispersible granulate (WG). Afterwards, the mortality of C. a. tingomariana adults was assessed. A conidia concentration of 2.9 × 109 conidia cm−2 was obtained after 9 days‐course fermentation and a yield of 33.4 g kg−1 dry‐substrate. Conclusions The polyester fabric‐based fermentation is an efficient technique for producing and collecting B. bassiana spores. Regarding LC90, the potency analysis showed that the EC was 21‐fold more potent than the non‐formulated conidia, and ~ 2.6‐fold more potent than the WG. Significance and impact of study A high throughput fermentation based on polyester fabric as support for B. bassiana conidia production and subsequent formulation as an EC comprises a promising strategy for obtaining a bioproduct to control adults of C. a. tingomariana and other Chrysomelidae pests.