Acute feeding disorder after oral RNAi exposure results in efficient pest control

ABSTRACT Oral feeding of RNA interference (f-RNAi) is an innovative technology in the protection of crops from herbivorous pests. The strength of this technology lies in choosing optimal f-RNAi targets. Conventional targets have been chosen on due to their induction of lethality or infertility in target pests. However, conventional targets are slow-acting (c.a. one week) and crop damage can progress until the induction of lethality due to f-RNAi. Here, we show that f-RNAi of death-associated inhibitor of apoptosis protein 1 (diap1) induces acute feeding cessation. In the solanaceous pest, Henosepilachna vigintioctopunctata, f-RNAi of diap1 caused a decrease in feeding leaf area during the first 24 hours after treatment. Feeding cessation in f-RNAi individuals was achieved during 24-48 hours. We compared our targets with conventional targets by analyzing the influence of frequently used target genes, vacuolar ATPase subunits A and E, and showed that unlike diap1 f-RNAi, conventional targets did not induce acute feeding disorder. Feeding experiments of diap1 double-stranded RNA (dsRNA) from other insects against H. vigintioctopunctata did not induce feeding cessation and showed high species-specificity of diap1 dsRNA. We also showed that 1.6 ng diap1 dsRNA is sufficient to induce acute feeding cessation in H. vigintioctopunctata. These results suggest that diap1 is an optimal target gene for rapid reduction of crop damage by herbivorous insects. In addition, our findings suggest that acute feeding cessation should be assessed as well as conventional criteria in selecting target genes for pest control by f-RNAi.