Double-stranded RNA (dsRNA) has been applied to control insect pests due to its induction of RNA interference (RNAi) of a specific target gene expression. Bacterial expression and formulation of dsRNA led to minimizing dsRNA degradation. In our studies overexpression of dsRNA specific to chymotrypsin, essential protease for the survival of the beet armyworm, Sopodoptera exigua, (SeCHY2) in Escherichia coli HT115 (DE3), was toxic to larvae after oral administration. In the other view, silencing of the transformer2 (tra-2) gene that seems to performance as the genetic modification generate female development in several dipteran species including the striped fruit fly, Baetrocera scutellata can used to development for male-only release technique to control of this pest.

RNAi (RNA interference) is a tool for silencing of target genes through sequence-specific manner. Spodoptera exigua belongs to Noctuidae family of Lepidoptera and is serious threat to crops of economic importance. One of S. exigua chymotrypsin gene (SeCHY2) was cloned into the L4440 vector to produce sequence specific dsRNAs (double-stranded RNAs). Recombinant L4440 vectors were transformed into Escherichia coli strain HT115 (DE3). Oral delivery of bacterially expressed dsRNA gave significant larval mortality. Quantitative real-time PCR results showed that expression level of target SeCHY2 gene in the larval gut tissue was significantly down-regulated. Pretreatment with an ultra-sonication and heating to disrupt bacterial cell wall/membrane significantly increased the insecticidal activity of the transformed bacteria