Assessing the effectiveness of imidacloprid and thiamethoxam via root irrigation against Megalurothrips usitatus (Thysanoptera: Thripidae) and its residual effects on cowpea

Abstract

Systemic neonicotinoid insecticides (NEOs) applied by seed-treatment or root application have emerged as a prevalent strategy for early-season insect pest management. This research investigated the effectiveness of imidacloprid and thiamethoxam, administered through root irrigation, in managing thrips in cowpea [Vigna unguiculata (Linn.) Walp.], and the residual properties of both insecticides in cowpea and soil. The results show that thrips density depends on the application rate of insecticides. At the maximum application rate (1,500 µg/ml, active ingredient), imidacloprid and thiamethoxam controlled thrips densities below the economic injury level (EIL, the EIL of thrips on cowpea was 7/flower) for 20 days and 25 days with the density of 6.90 and 6.93/flower at the end of the periods, respectively. Imidacloprid and thiamethoxam residues decreased gradually over time and decreased sharply after 15 days after treatment (DAT), the 2 insecticides were not detected (<0.001 mg/kg) at 45 DAT. According to our findings, the application of imidacloprid and thiamethoxam via root irrigation proved residual control lasting up to 20–25 days for controlling thrips damage at experimental rates, with a strong association to their residual presence in cowpea (0.6223 < R2 < 0.9545). Considering the persistence of the imidacloprid and thiamethoxam, the maximum tested application rate (1,500 µg/ml) was recommended. As the residues of imidacloprid and thiamethoxam were undetectable in cowpea pods at all tested rates, it may be suggested that the use of each insecticide is safe for consumers and effective against thrips, and could be considered for integrated thrips management in the cowpea ecosystem.

The Amino Acid Transporter PtCAT7 and Ammonium Nutrition Enhance the Uptake of Thiamethoxam in Citrus Rootstock Seedlings

“…Citrus trees produce multiple flushes within a year, such as in early spring, early summer, late summer, fall, and winter, coinciding with peak populations of ACP. THX, a systemic neonicotinoid insecticide, is widely applied in the fields by foliar spray, seed treatment, or root irrigation and can effectively control a variety of insects, such as S. frugiperda , Bemisia tabaci , and Megalurothrips usitatus . − Our previous study revealed that soil-applied THX was transported into citrus leaves, with higher amounts in new leaves than old leaves, and protected trees from ACP feeding for 60 to 90 days . THX was translocated to the upper part of plants via xylem mobility after being absorbed by the plant roots. , However, the molecular mechanisms of which genes or proteins are involved in xylem mobility remain unclear.…”