Frankliniella occidentalis is a major pest in agriculture. Following overuse of insecticides, high resistance has developed due to its high reproduction rate and short generation time. To control the resistant strains of the thrips, the ingestion RNAi- based control was established. A total of 67 genes were selected, and their double-stranded RNAs (dsRNA) were delivered to thrips via the leaf disc-feeding method. Among the genes screened, the dsRNA of Toll-like receptor 6 (TLR6) and coatomer protein subunit epsilon (COPE) resulted in the highest mortality (3.8- and 2.8-fold faster LT50 compared to control, respectively) when ingested by thrips. The dsRNA-fed thrips showed 53% and 83% reduced transcription levels of TLR6 and COPE, respectively. This result demonstrates that the observed mortality of thrips following dsRNA ingestion was due to RNAi, and this lethal genes can be employed as a practical tool to control thrips in the field.

Tetranychus urticae is extremely hard to control by conventional acaricides due to its rapid development of resistance to nearly all arrays of acaricide. As an alternative control measure of acaricide-resistant mites, RNA interference (RNAi)-based method has recently been suggested. A double-stranded RNA (dsRNA) delivery method using multi-unit chambers was established and employed to screen the RNAi toxicity of 42 T. urticae genes. Among them, the dsRNA treatment of coatomer I (COPI) genes, such as coatomer subunit epsilon (COPE) and beta 2 (COPB2), resulted in high mortality [median lethal time (LT50) = 89.7 and 120.3 h, respectively]. The transcript level of the COPE gene was significantly (F3,9 = 16.2, P = 0.001) reduced up to 24% following dsRNA treatment, suggesting that the toxicity was likely mediated by the RNAi of the target gene. To identify the deferentially expressed gene upon dsRNA ingestion, RNA-seq was employed to compare the transcriptional profiles between mites fed dsEGFP and dsCOPB2. Approximately 928 of genes were up- or down-regulated significantly (P < 0.05) compared to control and 182 genes were commonly responded to the treatment of both dsRNAs. Those dsRNA-responsible genes were mainly categorized into metabolic enzymes, transporters and secretory proteins. Further study would be necessary to elucidate the roles of dsRNA-responsible genes in mite’s dsRNA uptake and defense.