Assessment of cytisine as an insecticide candidate for Hyphantria cunea management: Toxicological, biochemical, and control potential insights

In the present study, the toxicological effects of cytisine on the H. cunea larvae were investigated, and the potential of cytisine as a botanical insecticide through field simulation experiments was evaluated. The results showed that cytisine treatment (0.25–2.5%) exerted significant biotoxic effects on the H. cunea larvae, including diminished weight, disruption of both positive (HcCKS1, HcPLK, HcCCNA) and negative (HcGADD and HcCDKN) regulatory genes associated with larval growth, increased mortality, and heightened oxidative damage (H2O2 and MDA). Cytisine treatment significantly reduced glucose content and inhibited the expression of key rate-limiting enzyme genes (HcPFK, HcPK, HcHK1, HcCS, and HcIDH2) within glycolysis and the tricarboxylic acid cycle pathways. Under cytisine treatment, detoxification enzyme activities (CarE and GST) and expression of detoxification genes (HcCarE1, HcCarE2, HcCarE3, HcGST1, and HcGST3) were inhibited in H. cunea larvae. An increased contents of SOD, CAT, ASA and T-AOC, as well as expression of antioxidant enzyme genes HcSOD1 and HcCAT2, was found in cytisine-treated H. cunea larvae. Simultaneously, this is accompanied by a significant reduction in the expression of four antioxidant enzyme genes (e.g., HcPOD1 and HcPOD2). In the field experiment, a cytisine aqueous solution (25 g/L) with pre-sprayed and directly sprayed ways demonstrated potent insecticidal activity against H. cunea larvae, achieving a mortality rate of 53.75% and 100% at 24 h, respectively. Taken together, cytisine has significantly weight inhibition and lethal toxicity on the H. cunea larvae, and can be developed as a botanical insecticide for H. cunea control.