Silencing of juvenile hormone‐related genes through RNA interference leads to molt failure and high mortality in the spongy moth

Abstract Lymantria dispar (spongy moth) is a globally polyphagous and destructive pest, with the larval stage being the main destructive stage. The larvae feed on more than 600 species of plants ranging from oaks to conifers, and they are capable of completely defoliating entire trees, leading to significant ecological and economic losses. Chemical insecticides are commonly used to control them, but these methods are expensive and nonspecific. Therefore, RNA interference (RNAi) is being explored as an alternative strategy to control spongy moth. Juvenile hormones (JHs) play a crucial role in regulating insect growth, diapause, and reproduction, making them potential targets for pest control. This study investigated whether 2 enzymes involved in the JH pathways—JH acid methyltransferase (JHAMT) from the biosynthetic pathway and JH epoxide hydrolase (JHEH) from the metabolic pathway—could be used for RNAi‐based control. Ldjhamt showed predominant expression during the larval stages and Ldjheh exhibited high expression throughout development. Both genes had the highest expression in the fat body. RNAi silencing using specific double‐stranded RNAs resulted in a significant decrease in the expression level of target genes, as well as a significant reduction in larval survival rate, pupation rate and eclosion rate. Additionally, many larvae and pupae died due to developmental abnormalities, and the adult size of the treated group was smaller than the control group. These findings demonstrate that jhamt and jheh are vital for the growth and development of spongy moths and suggest they could be effective targets for RNAi‐based pest control strategies.