Department of Plant Protection, Faculty of Agriculture, University of Zabol, Zabol, Iran,
Trialeurodes vaporariorum recently showed resistance to insecticides. In view of the recently interest in plant origin insecticides as an alternative to commercial insecticide, in this study, the insecticidal activity of green synthesized zinc oxide nanoparticles (ZO-NPs) using pure extracts of basil, cinnamon, eucalyptus, harmel, and oleander were examined. ZO-NPs were synthesized using a conventional method and then their effects were investigated on antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferases (GST)) of T. vaporariorum as an insect model under oxidative stress. The size, the morphology and characterization of Z0-NPs was studied. To find out concentrations with 10-90% mortality, primary tests were done with concentration ranges between 1-30 mg L-1 of pure plant extracts and their synthesized ZO-NPs. Two hundred adults of T. vaporariorum individuals were considered for each treatment. Five ml of the concentrations were sprayed on insect adults. To avoid precipitation of nanoparticles in solutions, before spraying, all prepared concentrations were sonicated for 10 min. Then, the insects were transferred to leaf cages installed over green bean leaves. The number of dead insects was counted after 24 h and mortality was computed for three replications of each treatment. Distilled water was used as control. Crude enzyme of survived adults was extracted by homogenizing adults (n=50) in 150 μL phosphate buffer, and centrifuging (10,000 g, 10 min). The supernatant as the enzyme source was stored at -20 °C. The observed peak at 455 nm confirmed the forming of ZO-NPs. Particles with 40 nm size and spherical shapes were observed. Results showed that oleander, harmel, and basil ZO-NPs effectively killed 50% of T. vaporariorum at 1.004, 2.425, and 3.981 mg L-1, respectively. Our results showed that LC50s of pure oleander, harmel, and basil extracts were 4.210, 7.983, and 13.116 mg L-1, which were less effective to kill 50% of T. vaporariorum compare to their ZO-NPs. Despite no significant changes in T. vaporariorum treated with LC50 doses of pure plant extracts separately, significant increases were observed in GST, CAT, and SOD activities in T. vaporariorum adults exposed to the LC50 of NPs. Our findings suggest that exposure to ZO-NPs induced oxidative stress in T. vaporariorum adults. The potential application of synthesized ZO-NPs using oleander, harmel, and basil in comparison to the pure plant extract to manage this pest in greenhouses and urban green spaces, as well as their applicable formulation for application in the field conditions, could be considered in the upcoming projects.