Non-invasive RNAi Delivery in Varroa and Psoroptes Mites

A non-invasive immersion technique for RNAi developed in Varroa destructor [23 (link)] was adapted for P. ovis using modifications [20 (link)]. Briefly, mites, or their eggs, were immersed in the detached cap of a 1.5 mL micro-centrifuge tube in 15 µL of a solution containing either a fluorophore-labelled AllStars™ Negative Control siRNA (Qiagen, UK) (“fluoro-siRNA”) in 0.9% w/v NaCl solution, final fluoro-siRNA concentration 0.05 µg/µL, or 15 µL 0.9% w/v NaCl solution only. The mites were incubated at 4 °C overnight then washed three times in molecular biology grade water (Sigma, UK) before photographic images were captured through an Axiovert 25 CFL inverted fluorescent microscope (Zeiss, Germany) with 10× Achrostigmat magnification lens (Zeiss, Germany) using a D90 AF-5 DX NIKKOR digital camera with 18–105 mm f/3.5–5.6 G ED VR lens kit (Nikon, Japan).