Assessment of lethal and sublethal effects of imidacloprid, ethion, and glyphosate on aversive conditioning, motility, and lifespan in honey bees (Apis mellifera L.).

Honeybees (Apis mellifera) play an important role in agriculture worldwide. Several factors including agrochemicals can affect honey bee health including habitat fragmentation, pesticide application, and pests. The growing human population and subsequent increasing crop production have led to widespread use of agrochemicals and there is growing concern that pollinators are being negatively impacted by these pesticides. The present study compares acute exposure to imidacloprid (0.2 and 0.4 mgL-1), ethion (80 and 106.7 mgL-1) or glyphosate (0.12 and 0.24 mgL-1) on aversive learning and movement, to chronic exposure at these and higher concentrations on movement, circadian rhythms, and survival in honey bee foragers. For acute learning studies, a blue/yellow shuttle box experiment was conducted; we observed honey bee choice following aversive and neutral stimuli. In learning studies, control bees spent >50% of the time on yellow which is not consistent with previous color bias literature in the subspecies or region of the study. The learning apparatus was also used to estimate mobility effects within 20 min of exposure. Chronic exposure (up to 2 weeks) with the above metrics was recorded by an automated monitoring system. In chronic exposure experiments, RoundUp®, was also tested to compare to its active ingredient, glyphosate. We found that imidacloprid and ethion have negative impacts on aversive learning and movement following a single-dose and that chronic exposure effects were dose-dependent for these two insecticides. In contrast, glyphosate had no effect on learning and less of an effect on movement; RoundUp® showed dose-dependent results on circadian rhythmicity. Overall, the results suggest that short-term exposure to imidacloprid and ethion adversely affect honey bee foragers and chronic exposure to glyphosate may affect pollination success.

Toxicological and biochemical characterizations of AChE in phosalone-susceptible and resistant populations of the common pistachio psyllid, Agonoscena pistaciae.

The toxicological and biochemical characteristics of acetylcholinesterases (AChE) in nine populations of the common pistachio psyllid, Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Psyllidae), were investigated in Kerman Province, Iran. Nine A. pistaciae populations were collected from pistachio orchards, Pistacia vera L. (Sapindales: Anacardiaceae), located in Rafsanjan, Anar, Bam, Kerman, Shahrbabak, Herat, Sirjan, Pariz, and Paghaleh regions of Kerman province. The previous bioassay results showed these populations were susceptible or resistant to phosalone, and the Rafsanjan population was most resistant, with a resistance ratio of 11.3. The specific activity of AChE in the Rafsanjan population was significantly higher than in the susceptible population (Bam). The affinity (K(M)) and hydrolyzing efficiency (Vmax) of AChE on acetylthiocholine iodide, butyrylthiocholine iodide, and propionylthiocholine odide as artificial substrates were clearly lower in the Bam population than that in the Rafsanjan population. These results indicated that the AChE of the Rafsanjan population had lower affinity to these substrates than that of the susceptible population. The higher Vmax value in the Rafsanjan population compared to the susceptible population suggests a possible over expression of AChE in the Rafsanjan population. The in vitro inhibitory effect of several organophosphates and carbamates on AChE of the Rafsanjan and Bam populations was determined. Based on I50, the results showed that the ratios of AChE insensitivity of the resistant to susceptible populations were 23 and 21.7-fold to monocrotophos and phosphamidon, respectively. Whereas, the insensitivity ratios for Rafsanjan population were 0.86, 0.8, 0.78, 0.46, and 0.43 for carbaryl, eserine, propoxur, m-tolyl methyl carbamate, and carbofuran, respectively, suggesting negatively correlated sensitivity to organophosphate-insensitive AChE. Therefore, AChE from the Rafsanjan population showed negatively correlated sensitivity, being insensitive to phosphamidon and monocrotophos and sensitive to N-methyl carbamates.

Residue kinetics of neonicotinoids and abamectin in pistachio nuts under field conditions: model selection, effects of multiple sprayings, and risk assessment.

Pistachio is an economically valuable crop, and Iran is among the biggest producers, exporters, and consumers of this product in the world. During the growing season, pistachios are subjected to multiple sprayings with various pesticides, which result in the accumulation of their residues in nuts. These residues have raised concerns regarding consumers' health. In this research, uptake and dissipation kinetics of insecticides imidacloprid (IMI), thiacloprid (THI), thiamethoxam (THX), and abamectin (ABA) were investigated in pistachio nuts. Field experiments were conducted in a pistachio orchard. Pistachio trees were sprayed with the recommended dose of each insecticide formulation and water as the control. Samplings were performed for up to 49 days. Based on the results, pesticides uptake and dissipation kinetics were best fitted to first-order exponential growth (FOEG) and single first-order kinetic (SFOK) models, respectively. Variations in pesticides uptake/dissipation rates were mostly related to their water solubility, pKa, and log Kow. THX showed a higher uptake rate (0.16 ± 0.04) compared to IMI (0.10 ± 0.01) and THI (0.06 ± 0.01). The fastest dissipation rates were observed for IMI (0.04 ± 0.002 day-1) and THX (0.03 ± 0.001 day-1), while the slowest belonged to THI (0.02 ± 0.003 day-1). ABA residues were below the quantification limit (LOQ) throughout the experiment. Based on FOEG and SFOK model predictions, multiple sprayings with THI and THX resulted in final concentrations exceeding the maximum residue limit (MRL). Hazard quotients for all pesticides were <1, indicating no risk to humans via consumption of the pistachio nut.