Influence of Pesticide Application Method, Timing, and Rate on Contamination of Nectar with Systemic and Nonsystemic Pesticides.

This article investigates how pesticide management practices during ornamental plant production affect contamination of nectar, focusing on the systemic insecticide thiamethoxam and the nonsystemic fungicides boscalid and pyraclostrobin in Salvia 'Indigo Spires.' The study found that nectar contamination with thiamethoxam and its metabolite clothianidin was significantly influenced by application method (drench vs. spray), timing (prebloom vs. postbloom), and rate, with drench applications resulting in substantially higher concentrations that often exceeded published median lethal concentrations (LC50s) for native bees and honeybees, indicating acute toxicity risks. In contrast, the nonsystemic fungicides were detected at much lower concentrations, below levels associated with observable toxic effects. These findings highlight the importance of optimizing pesticide application practices in ornamental plant production to reduce pollinator exposure to systemic insecticides while maintaining pest control.