Dose-dependent lethality of sulfuryl fluoride and transcriptomic insights into tolerance evolution on Cheyletus malaccensis (Oudemans) (Acari: Cheyletidae)

The use of the predatory mite Cheyletus malaccensis (Oudemans) for controlling stored grain pests represents an ecologically sustainable biocontrol strategy, while sulfuryl fluoride fumigation serves as an effective chemical control method. This study investigates the feasibility of combining C. malaccensis with sulfuryl fluoride fumigation to manage stored grain pests. Additionally, we employ transcriptomic analysis to elucidate the physiological and metabolic mechanisms that C. malaccensis engages under stress conditions. Under the same fumigation duration, the mortality rates of both adult and egg increased with higher concentrations of sulfuryl fluoride. The LC₅₀ for adult mites after 48 h of fumigation was approximately 1.58 g/m³, while the LC₅₀ for egg was around 26.48 g/m³. When the fumigation time for egg was extended to 60 h, the mortality rate at a concentration of 25 g/m³ increased by approximately 1.4 times; after 72 h, the mortality rate at 15 g/m³ rose by 3.6 times. Egg exhibited greater tolerance to sulfuryl fluoride fumigation compared to adult. Neither adult nor egg could survive in high-concentration, long-duration fumigation environments. C. malaccensis can be released after the fumigation has dissipated (with sulfuryl fluoride concentrations not exceeding 2.3 g/m³), allowing it to effectively establish populations in real storage facilities for long-term control. In the transcriptome data, a total of 4730 differentially expressed genes were identified, including 3489 upregulated and 1241 downregulated genes. Through GO and KEGG analysis, it was found that the pathways involved in lipid metabolism and energy metabolism processes, pathogen infection and immune response were significant.