Alginate–Bentonite Beads Containing Thiamethoxam: Preparation, Characterization, and Activity against Brevicoryne brassicae

Abstract Brevicoryne brassicae is an important pest of brassica crops, and thiamethoxam is widely used for its control. This study prepared alginate–bentonite beads containing thiamethoxam and evaluated their physicochemical characteristics, aqueous recovery profile, soil-column leachate profile, and insecticidal activity against B. brassicae. X-ray diffraction, ATR-FTIR, TGA–DTG, and scanning electron microscopy characterized the matrix, while HPLC established an extractable thiamethoxam content of 1.219 ± 0.049 mg g–1. In the aqueous assay, the fraction recovered from the medium was lower for the bead formulation than for Actara 250 WG over the documented 48 h interval. Recalculation of the soil-column records gave cumulative fractions of 81.13 ± 1.12% for the bead formulation and 94.15 ± 6.91% for Actara 250 WG on day 30 (n = 4). The bead treatment produced high mean mortality of B. brassicae at the evaluated challenge times. However, the formulations were not applied at equivalent thiamethoxam amounts, and the experiments did not include a complete soil-column mass balance or formal equivalence or noninferiority analyses. The results therefore demonstrate different behavior under the tested conditions but do not establish superior performance, prolonged insect control, groundwater protection, or reduced environmental impact.