Ostrinia fuacalis (Lepidoptera:Pyralidae) is one of the most destructive agricultural pests in Asia.Traditional pest-management methods include sex pheromone capture,transgenic crops that produce Bacillus thuringiensis toxin,and pesticides.Although these strategies control pest populations effectively,they also cause negative side effects,including dramatically increased pesticide resistance,severe pollution,and hazards for human health.Recently developed genome editing tools provide new prospects for pest management and have been successfully used in several species.However,few examples have been reported in the agricultural pest O.fuacalis due to a lack in genomic information.In this report,we identified only one transcript of O.fuacalis Argonaute 1 (OfAgo1) gene from the genome and cloned the open reading frame.Of Ago1 presented the maximum expression at the embryo stage or in the fat body during the larval stages.To understand its function,an Of Ago1 mutant was constructed using the Clustered Regularly Interspaced Short Palindromic Repeat/RNA-guided Cas9 nuclease (CRISPR/Cas9).Mutagenesis of Of Ago1 disrupted cuticle pigmentation by down-regulating micro RNAs and pigmentation-related genes.This is the first report for the cloning and functional analysis of Of Ago1,revealing a role of Of Ago1 in cuticle pigmentation.The current report also established a CRISPR/Cas9 system in O.fuacalis,providing a new insight for pest management.