| Popis: |
The two-spotted spider mite, Tetranychus urticae Koch is the most destructive phytophagous mites that attack a broad range of host plant species. The excessive application of pesticides increases the pollution levels of the environment, requiring the essentiality to find out alternative substances that do not cause ecological damages. In this context, the toxicity of titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles (NPs) compared to abamectin against adult females of T. urticae was evaluated at different exposure times under laboratory and greenhouse conditions. Effects of tested nanoparticles on the development and reproduction of T. urticae as well as their side effects on the predatory mite, Neoseiulus californicus were also assessed. In laboratory bioassays, TiO2 NPs and ZnO NPs were less toxic than abamectin against adult females of T. urticae, LC50 values were 117.0 and 146.6 mg L –1, respectively compared to 4.9 mg L –1 in abamectin, respectively 72 hr post-treatment. Compared to the normal parameters, TiO2 and ZnO had a prolongation effect on both the developmental and reproductive durations with mean life spans of 33.18±0.72 days and 30.53±0.82 days in the case of TiO2 NPs and ZnO NPs, respectively compared to 24.65±0.53 days in the normal case. Treated T. urticae females produced lesser fecundities (10 –22 eggs less than the normal mean) and decreased hatchability rates. The highest reduction percentages in T. urticae populations were 92.4% and 90.0% after the first day of spraying with TiO2 NPs and ZnO NPs, respectively, compared to 98.4% in abamectin, while assessed nanoparticles demonstrated less toxicity on N. californicus populations. The obtained findings suggest that both TiO2 NPs and ZnO NPs may be recommended as alternatives to traditional acaricides for T. urticae control with keeping on environmental safety. This is the first study to investigate the control of T. urticae mites infesting cucumber plants in Egypt and the effects on their biology and natural enemies. |
