Insight into the Long-Lasting Control Efficacy of Neonicotinoid Imidacloprid against Wheat Aphids during the Entire Growth Period

Abstract

Understanding the mechanism of long-lasting control efficacy of pesticides is important for developing sustainable high-efficacy pesticides, decreasing pesticide-use frequency and environmental input. This study investigates the long-term control mechanism of imidacloprid against wheat aphids under seed treatment. The concentrations of imidacloprid and its metabolites were 2.2−69.6 times lower than their individual LC 50 after 238 days of treatment, and the control efficacy was still higher than 94.6%. The mixed bioactivity tests demonstrated that the insecticidal activity of the mixture of imidacloprid and its bioactive metabolites was approximately 1.5−189.7 times greater than that of a single compound against wheat aphids. The concentrations of imidacloprid, 5hydroxy imidacloprid, and imidacloprid olefin in top flag leaves were 0.022, 0.084, and 0.034 mg/kg, respectively, during the aphid flourishing period, which were higher than the LC 50 of the mixture (0.011 mg/kg), therefore providing long-lasting control efficacy.The study provides a first insight into the synergistic effects between a pesticide and its bioactive metabolites in ensuring long-term control performance.

From Water to Water: Insight into the Translocation of Pesticides from Plant Rhizosphere Solution to Leaf Guttation and the Associated Ecological Risks

“…After 10 days of growth, four uniformly sized maize plants (root length of 15 ± 1 cm; shoot height of 30 ± 1 cm) were transferred to a glass container containing 1 L of nutrient solution with spiked pesticides at 500 μg/L for each pesticide. This exposure level represents a reasonable level for these pesticides in agricultural environments. − Two types of controls were included: a pesticide-free control (maize plant only) and a pesticide-spiked solution control (without plants). All experiments were conducted in triplicate.…”