Insights into the uptake, translocation, and accumulation dynamics of cyantraniliprole and thiamethoxam seed coating pesticides in maize plants.

Abstract

Seed coating with pesticides is used extensively for the protection of both seeds and plants against pests. In this study, the uptake and transport of seed-coating pesticides (insecticides), including cyantraniliprole (CYN) and thiamethoxam (THX), were investigated. The translocation of these pesticides from the soil to the plant and their accumulation in different plant parts were also calculated. After sowing the seeds with seed coating pesticides, soil and plant samples were taken across the study area. These samples were extracted and analyzed in liquid chromatography with tandem mass spectrometry (LC-MS/MS). CYN and THX were used in maize plants for the first time to observe soil degradation kinetics, and CYN showed a higher half-life than THX in soil. Both pesticides have been taken up by the corn maize plant and transferred and accumulated to the upper parts of the plant. Although the THX concentration was between 2.240 and 0.003mg/kg in the root, between 3.360 and 0.085mg/kg in the stem, it was between 0.277 and 3.980mg/kg in the leaf, whereas CYN was detected at higher concentrations. The concentration of CYN was 1.472mg/ kg and 0.079mg/kg in the roots and stems of the maize plant, respectively. However, the bioconcentration factor (BCF) indicates the soil-to-plant accumulation of CYN from 28 to 34.6 and that of 12.5 to 4567.1 for THX on different sampling days. The translocation factor (TFstem) represents the ratio of pesticides absorbed from the stem and transported to the roots. For CYN, TFstem ranges from 3.6 to 20.5, while for THX, it varies between 1.5 and 26.8, indicating a higher translocation rate for THX. The ratio of leaf to root concentration are 3.6 to 20.5 for CYN and 1.8 to 87.7 for THX, demonstrating effective translocation for both pesticides. The TF values for both pesticides are above 1, signifying successful root-to-stem-to-leaf movement. Notably, THX exhibits a notably higher transport rate compared to CYN.