Dissipation kinetics and risk assessment of thiamethoxam and dimethoate in mango

Abstract

Thiamethoxam and dimethoate are two insecticides used to control hoppers and inflorescence midges in mango. Thiamethoxam (0.008 and 0.016%) and dimethoate (0.06 and 0.12%) were sprayed on Dashehari mango trees during the pre-mature stage of fruit (first week of May) to study their dissipation kinetics and risk assessment in mango fruit. Thiamethoxam dissipated in fruit from 1.93 and 3.71 mg kg(-1) after 2 h of spraying to 0.08 and 0.13 mg kg(-1) after 20 days of spraying at single and double doses, respectively. Its residue did not persist beyond 20 days in fruit. Dimethoate dissipated in fruit from 2.81 and 5.34 mg kg(-1) after 2 h of application to 0.12 and 0.19 mg kg(-1) after 10 days of application at single and double doses, respectively. No residue was detected in fruit beyond 10 days after its application. Both ready-to-harvest mature mango fruit and pulp (after 40 days of spraying) were free from any residues of these insecticides at both the concentration levels. The rate of dissipation of these insecticides followed first-order kinetics in fruit with residual half-lives of 4.0 to 4.5 days for thiamethoxam and 2 days for dimethoate. Based on their MRL values of 0.5 and 2.0 mg kg(-1) in mango, pre-harvest intervals of 7 and 11 days, and 6 and 7 days were suggested for thiamethoxam and dimethoate, respectively, after spraying at single and double doses. The theoretical maximum residue contribution (TMRC) values for both the insecticides, calculated for residues corresponding to each sampling date, were found to be below the maximum permissible intake (MPI) values on mango fruit (except for dimethoate double dose up to 3 days); hence, both thiamethoxam and dimethoate could be considered non-hazardous to consumers at the above doses and time intervals.

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 1: new molecules, metabolism, fate, and transport

“…After 20 days, residues declined to 80 and 130 ppb for the single and double applications, and no residues were detected after 40 days. This suggests that preharvest withholding periods of 7 to 11 days do comply with the maximum residue limit (500 ppb) for this produce (Bhattacherjee and Dikshit 2016). Balfour et al (2016) measured residues of thiamethoxam and its main metabolite clothianidin in oilseed rape and maize grown from treated seeds.…”

Residual dynamics and dietary exposure risk of dimethoate and its metabolite in greenhouse celery

“…Previous studies found that the half-life of dimethoate in the open field is 2.5 days (Guo et al, 2017), indicating that the residual level of dimethoate is not significantly different in the greenhouse and in the field. The half-life of dimethoate in mango is 2 days (Bhattacherjee & Dikshit, 2016), and the half-life in cucumber is 5.2 days (Geng et al, 2018), indicating that the dissipation of dimethoate is related to the matrix on which it is applied. The half-life of dimethoate in celery grown in Guizhou is 5.4 days, and the half-life of celery in Anhui is 3.5 days (Chen et al, 2018).…”

Persistence and dissipation behavior of pesticide residues in parsley (Petroselinum crispum) under field conditions

“…The half-life of dimethoate in our study (3.30 days) was lower than that reported for chilly (4.7 days) and okra (5.21 days) (Waghulde et al, 2011). The PHI of dimethoate in parsley (132 days) was higher than that in papaya (3-5 days), guava (3 days), and mango (6-7 days), while it was lower than that in chili (13.63 days) and pomegranate (31.5 days at the standard dose of application and 43.0 days at a double dose of application) (Ahuja et al, 2005;Bhattacherjee and Dikshit, 2016;Khan et al, 2009;Utture et al, 2012;Varghese et al, 2011).…”