Nanotechnology takes a significant position in controlling pests. Silicon dioxide nanoparticles (SiO2-NPs) is considered one of the best alter-natives to chemical pesticides for plant crop protection from harmful arthro-pods such as phytophagous mites, Tetranychus urticae. Therefore, this study aims to evaluate the effect of (SiO2-NPs) to control T. urticae. Under green-house conditions, the results revealed, in the larval stage, a high mortality percentage (99.05±0.83%) followed by eggs (98.74±1.22%). Besides, the nymph stage recorded high mortality (94.66±1.81%) at a high concentration of 1500 ppm. While the adult females of T. urticae recorded mortality of 91.92±1.02% after 72h. Eventually, the immature stages of T. urticae were susceptible to (SiO2-NPs). Meanwhile, at laboratory evaluation on immature stages of T. urticae which resulted from live treated females during 96h showed a sharp decrease in average numbers of eggs through 96h, at 1000 and 1500 ppm. No numbers of the larval stage were recorded at 1500 ppm. No number of nymph stage were recorded at all concentrations and periods. Moreover, activity of AChE was significantly inhibited at 1500 ppm, while activity of glutathione-S-transferase was significantly increased after 72 h. Finally, (SiO2-NPs) are effective against immature stages of T. urticae under greenhouse and laboratory conditions.

A field experiment was conducted during autumn plantation in season 2017 at Qaha, Qalubiya Governorate to evaluate the efficiency of ten different control agents; four of them are biorational components (garlic extract, rosemary oil + sunflower oil, sesame oil and chili oil), three of them are natural pesticide (Techno Oil, Top9 and Berna Star), one agent of them is bio-pesticide (bio-fly) and two chemical pesticide (Blanch 48% SC, Mospilan 20% SP) in reducing the population densities of Bemisia tabaci and Tetranychus urticae on Hatma potato cultivar. The results indicated that there were significant differences between the ten tested compounds in reducing the population density of B. tabaci nymphs; Mospilan 20% SP was the most potent compounds in reducing the population density of B. tabaci nymphs causing the highest reduction percentage (83.58 %), while Top9 gave a low effect with reduction percentage (49.32%) and Bio-fly gave moderate reduction percentage (63.92%). These compounds could be divided into two groups according to the reduction percentage: 1st group contains Mospilan 20% SP, Blanch 48% SC (chemical pesticides), Berna Star and Techno Oil (natural pesticides), respectively. 2nd group contains on Bio-fly (bio-pesticide), sesame oil, garlic extract, chili oil, rosemary oil + sunflower oil (biorational components), and Top9 (natural pesticide) on B. tabaci nymphs. Results also revealed that there were significant differences between the mean of general reduction percentage of the ten tested compounds on T. urticae population. Mospilan 20% SP recorded the highest reduction percentage (73.1 %), (rosemary oil + sunflower oil) treatment recorded the lowest reduction percentage 41.97% and Top9 gave moderate reduction percentage (60.03%). These compounds could be divided into two groups: 1st group contains on Mospilan 20% SP, Techno Oil, Blanch 48% SC, garlic extract, Top9, chili oil, sesame oil and Berna Star respectively. 2nd group contains on Bio-fly and (rosemary oil + sunflower oil) respectively