Chitin Deacetylase 8 Affects Epidermal and Peritrophic Membrane Metabolism in Tuta absoluta and dsRNA Accelerates Larval Death with Bacillus thuringiensis

Tuta absoluta is highly resistant to many common insecticides. Chitin deacetylase (CDA), an important enzyme in chitin synthesis and metabolism, may serve as a target for the management of T. absoluta. We cloned and identified TaCDA8 using the polymerase chain reaction (PCR) and bioinformatics analysis. Quantitative real-time PCR (qRT-PCR) showed that the expression level of TaCDA8 in the fourth instar larvae was significantly higher than in other developmental stages. Feeding ds TaCDA8 significantly reduced larval survival and pupation rates, causing failed molting, impaired pupation, and peritrophic membrane (PM) damage. Combining dsRNA with a Bacillus thuringiensis (Bt) biopesticide agent increased mortality. These results confirm that TaCDA8 regulates chitin metabolism in the PM and is key for epidermal development. TaCDA8 is essential for larval growth, development, and resistance to pathogens. TaCDA8 can be effectively targeted by the RNAi-Bt combination to enhance pest mortality. Therefore, TaCDA8 represents a promising target for the development of highly efficient pesticides and green control strategies for integrated pest management.