Oral delivery of dsHvUSP is a promising method for Henosepilachna vigintioctopunctata control with no adverse effect on the non-target insect Propylea japonica

The 28-spotted potato ladybeetle Henosepilachna vigintioctopunctata is a prominent horticultural pest. RNA interference (RNAi) has been found as a novel management strategy for controlling this pest. The ultraspiracle protein (USP) plays a crucial role in the insect molting process by activating the primary 20-hydroxyecdysone (20E) response genes. In this study, functional characterization of Ultraspiracle in H. vigintioctopunctata (HvUSP) has been carried out via dietary RNAi. The results revealed silencing of HvUSP caused significant mortality in the 1st instars, while impairing the molting process in the 4th instars. In the female adults, HvUSP silencing resulted in a prolonged pre-oviposition time and a significant reduction in egg numbers. The effects of dsHvUSP were evaluated on Propylea japonica, a closely related species to H. vigintioctopunctata to analyze any non-target effects. The feedings of dsHvUSP and dsPjUSP to P. japonica 4th instars had no transcriptional or organismal effects, however, injection of the dsPjUSP hampered the larvae molting to pupae. Conversely, injection of dsHvUSP into the H. vigintioctopunctata larvae disabled the molting into the pupal stage, whereas injection of dsPjUSP casued no significant changes. Overall, our results revealed that feeding of dsHvUSP could induce a strong RNAi effect with no adverse effects on P. japonica and can be used as a target for the RNAi-based biocon-trol of H. vigintioctopunctata.