Oral RNAi to control Drosophila suzukii: laboratory testing against larval and adult stages

The spotted wing Drosophila (Drosophila suzukii) is an invasive and serious economic pest to small and stone fruits and its control is difficult. RNA interference (RNAi) or double-stranded RNA (dsRNA)-mediated gene silencing is rapidly becoming a widely used functional genomics tool in insects and holds great potential for insect pest control. This study investigates whether RNAi is functional in D. suzukii and whether oral delivery of dsRNA can elicit gene silencing and insecticidal activity. Firstly, microinjection of dsRNA targeting two essential genes (alpha COP and shrb) into the haemolymph of adult flies was performed, confirming that the RNAi system is functional and that gene silencing results in mortality. Secondly, dsRNA targeting alpha-COP and two extra essential genes, rpl13 and vha26, was mixed with artificial diet and fed to the larval and adult stages of D. suzukii. With naked dsRNA, no clear silencing and mortality were scored. However, combining dsRNA with a transfection reagent led to a significant increase in gene silencing and insect mortality. The best results were obtained with ds-Vha26. The results are discussed in relation to future optimization of the production, formulation, combinations and delivery of dsRNA.