Acaricidal Effects of Silicon Oxide and Zinc Oxide Nanoparticles against Tetranychus urticae (Acari: Tetranychidae) on Tomato Plants

ABSTRACT The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the world's most damaging agricultural pests. Nanoparticles have become one of the most promising new tools for pest management in recent years, but their efficacies against T. urticae are poorly known. We conducted laboratory and greenhouse experiments to evaluate the efficacy of commercially available silicon oxide nanoparticle (SiO-NP) and zinc oxide nanoparticle (ZnO-NP), each applied at 5, 50 and 100 ppm, on the adult and egg stages of T. urticae on tomato, Solanum lycopersicum L. (Solanaceae). In the laboratory experiment, SiO-NP and ZnO-NP at 100 ppm caused 100% mortality among female adult mites at 72 h after treatment and among eggs at 7 d post-treatment. In the greenhouse experiment, SiO-NP and ZnO-NP at 50 and 100 ppm caused withered plants, whereas treatment at 5 ppm did not cause any phytotoxicity and decreased mite densities to 0.25 adult/leaf and 0.4 egg/leaf on SiO-NP-treated plants and 0 adult/leaf and 0.3 egg/leaf on ZnO-NP-treated at 7 d post-treatment. Mite densities at 7 d post-treatment were 1.8 adult/leaf and 1.7 egg/leaf on untreated plants. Average percentage of leaf area damaged was 25% on the untreated plants, and 0.7% and 0.9% on plants treated with SiO-NP and ZnO-NP at 5 ppm, respectively. These results suggest that application of SiO-NP and ZnO-NP at 5 ppm can be used as eco-friendly management strategy of T. urticae.