Residues and dissipation kinetics of two imidacloprid nanoformulations on bean (Phaseolus vulgaris L.) under field conditions

The current study investigates the dissipation kinetics of two imidacloprid (IMI) nanoformulations (entitled: Nano-IMI and Nano-IMI/TiO2) on common bean (Phaseolus vulgaris) seeds under field conditions and compares them with 35% Suspension Concentrate (SC) commercial formulation. To do so, it sprays P. vulgaris plants at 30 and 60 g/ha within green bean stage, sampling them during the 14-day period after the treatment. Following extraction and quantification of IMI residues, dissipation data have been fitted to simple-first order kinetic model (SFOK) and to first-order double-exponential decay (FODED) models, with 50% and 90% dissipation times (DT50 and DT90, respectively) assessed along the pre-harvest interval (PHI). With the exception of Nano-IMI at 60 g/ha, other decline curves are best fitted to the FODED model. In general, dissipation is faster for Nano-IMI (at 30 g/ha: DT50 = 1.09 days, DT90 = 4.30 days, PHI = 1.23 days; at 60 g/ha: DT50 = 1.29 days, DT90 = 4.29 days, PHI = 2.95 days) and Nano-IMI/TiO2 (at 30 g/ha: DT50 = 1.15 days, DT90 = 4.40 days, PHI = 1.08 days; at 60 g/ha: DT50 = 0.86 days, DT90 = 4.92 days, PHI = 3.02 days), compared to 35% SC (at 30 g/ha: DT50 = 1.58, DT90 = 6.45, PHI = 1.93; at 60 g/ha: DT50 = 1.58 days, DT90 = 14.50 days, PHI = 5.37 days). These results suggest the suitability of Nano-IMI and Nano-IMI/TiO2 application at both rates in terms of their residues on P. vulgaris seeds

Cellular energy allocation of Glyphodes pyloalis (Lep.: Pyralidae): changes related to exposure to TiO2 nanoparticles

In order to study the pollution potential of TiO2 nanoparticles (TiO2-NPs) on ecological health, this research was carried out on the cellular energy allocation (CEA) of Glyphodes pyloalis Walker exposed to TiO2-NPs. The newly ecdysed fifth instar larvae of G. pyloalis were treated with LC10, LC20, LC30, LC40 and LC50 concentrations of TiO2-NPs and the amount of energy available (Ea), energy consumption (Ec) and cellular energy allocation were compared. The resulting calculated energy reserves (lipid, carbohydrate, glycogen and protein) showed that increasing the time of exposure, the total lipid and carbohydrate amounts significantly decreased, when the LC30, LC40 and LC50 concentrations were applied. The amounts of glycogen in the larvae treated with LC10, LC20 and LC30 concentrations of TiO2-NPs were increased, whereas the LC40 and LC50 concentrations led to decrease in the amount of glycogen. The significant reduction in the amount of total protein compared to the control and over all three days of treatment was observed for LC50 concentration of TiO2-NPs; however, the LC10 concentration lead to a significant increase of the total protein after three days. Ea decreased in a dose-response related manner and over all time points, but it significantly increased in treated larvae by LC10 and LC20 concentrations after two days. Ec increased as concentrations grew to LC30 and then started to decrease. The results showed that CEA was not affected by LC10 concentration, but significantly decreased when the concentration increased and at all time points probably as a cost to deal with TiO2-NPs detoxification. Therefore, it will be possible to use the CEA as an appropriate early biomarker for the impacts of TiO2-NPs

Biochemical biomarkers of Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) in exposure to TiO2 nanoparticles

Biochemical biomarkers and bioassays, due to their assumed immediate response after acute exposure of the organism to the stressor, are useful tools to gauging anthropogenic impacts. The toxicity of TiO2-nanoparticles (TiO2-NPs) on the Glyphodes pyloalis Walker was assessed and the LC50 value obtained as 660.85 mg/L. The in vivo responses of G. pyloalis to sub-lethal concentrations of TiO2-NPs were surveyed by monitoring the activity of general esterases (EST), peroxidase (POD) and glutathione S-transferase (GST), as biochemical biomarkers. Activity of these biomarkers affected by exposure to TiO2-NPs and this could lead to the mortality or sub-lethal impacts. The effect of TiO2-NPs concentrations on the activity of these enzymes was correlated to the exposure time. The activity of EST and GST was significantly decreased compared to the control, after 24 h of treatments. By increasing exposure time, the expression of EST and GST was significantly increased. More POD expression was occurred at low concentrations (i.e. LC20 and LC30); however, at high concentrations, less POD activity obtained. It can be concluded that these enzymes are good early indicator of toxicity and in conjunction with acute toxicity studies allow adverse effects of TiO2-NPs to be predicted and managed