Sublethal and transgenerational effects of fenoxycarb and novaluron on Asian citrus psyllid, Diaphorina citri ( Kuwayama ) ( Hemiptera: Psyllidae )

BACKGROUND: The Asian citrus psyllid, Diaphorina citri Kuwayama, is the primary vector of 'Candidatus Liberibacter' species causing citrus Huanglongbing. Sublethal effects of the insect growth regulators fenoxycarb and novaluron on this pest remain poorly characterized. We evaluated their sublethal and transgenerational effects on D. citri by integrating toxicity bioassays, age-stage, two-sex life tables and transcriptome sequencing. RESULTS: Toxicity to nymphs was stage- and application-method-dependent: fenoxycarb was more toxic than novaluron to fifth-instar nymphs under spray treatment but not under topical application, and younger instars were more susceptible than older instars. Sublethal doses (LD₁₀ and LD₃₀) stimulated reproduction in surviving F₀ adults (higher R₀ and longer T) but reduced the intrinsic (r) and finite (λ) rates of increase because the prolongation of T outweighed the gain in R₀. In the F₁ generation, fecundity and R₀ decreased under fenoxycarb (with a smaller, non-significant reduction under novaluron), whereas r and λ increased owing to shortened generation time. Thus, population parameters changed in different directions rather than showing uniform inhibition. LD₃₀ prolonged F₁ nymphal development, with the direction of the dose-response differing between the two insecticides. Transcriptome analysis identified 745 and 2484 differentially expressed genes under fenoxycarb and novaluron treatments, respectively; changes in the expression of hormone-signaling, chitin-metabolism and reproduction-related genes represent transcriptional associations rather than validated mechanisms. CONCLUSION: Fenoxycarb and novaluron exert transgenerational sublethal effects on D. citri. With the divergent transcriptional responses, these laboratory-based findings provide a basis for designing application and resistance-management strategies for D. citri, pending field or semi-field validation. © 2026 Society of Chemical Industry.