Assessment of imidacloprid in Brassica environment

Dissipation kinetics of alpha-cypermethrin and lambda-cyhalothrin residues in aboveground part of white mustard (Sinapis alba L.)

Dissipation of simultaneously applied insecticides alpha-cypermethrin and lambda-cyhalothrin was studied in a minor crop, aboveground part of white mustard (Sinapis alba L.). A validated gas chromatographic method (GC-ECD/NPD) was used to determine insecticide residues. Analytical performances were very satisfactory, with expanded uncertainties not higher than 14% (coverage factor k = 2, confidence level 95%). Dissipation of alpha-cypermethrin and lambda-cyhalothrin in white mustard followed first-order kinetics (R(2) between 0.953 and 0.995), with half-lives of 3.1-4.6 and 2.9-3.7 days respectively. Based on the results of this two-year study and the relevant residue regulation, alpha-cypermethrin and lambda-cyhalothrin treatments can be considered safe for crop protection, feeding animals and the environment.

Estimation of β-cyfluthrin and imidacloprid in okra fruits and soil by chromatography techniques

Dissipation of β-cyfluthrin and imidacloprid in okra was studied following three applications of a combination formulation of Solomon 300 OD (β-cyfluthrin 9 % + imidacloprid 21 %) @ 60 and 120 g a.i. ha(-1) at 7 days interval. Residues of β-cyfluthrin and imidacloprid in okra were estimated by gas liquid chromatography (GLC) and high performance liquid chromatography (HPLC), respectively. Residues of β-cyfluthrin were confirmed by gas chromatograph-mass spectrometry (GC-MS) and that of imidacloprid by high performance thin layer chromatography (HPTLC). Half-life periods for β-cyfluthrin were found to be 0.91 and 0.68 days whereas for imidacloprid these values were observed to be 0.85 and 0.96 days at single and double the application rates, respectively. Residues of β-cyfluthrin dissipated below its limit of quantification (LOQ) of 0.01 mg kg(-1) after 3 and 5 days at single and double the application dosage, respectively. Similarly, residues of imidacloprid took 5 and 7 days to reach LOQ of 0.01 mg kg(-1), at single and double dosages respectively. Soil samples collected after 15 days of the last application did not show the presence of β-cyfluthrin and imidacloprid at their detection limit of 0.01 mg kg(-1).

Bioefficacy, dissipation kinetics and safety evaluation of selected insecticides in Allium cepa L

This paper reports the bioefficacy of selected insecticides against thrips and their pre-harvest intervals (PHI) in onion pertaining to their recommended application rates and maximum residue limits. Profenophos, methomyl and imidacloprid showed comparatively higher bioefficacy against thrips. GC-MS and LC-MS/MS-based residue analysis methods in onion bulbs and composite matrix of bulbs+leaves were thoroughly validated. The residue data for bulb+leaves was assessed with reference to the EU-MRLs applicable for spring onion. Dimethoate was the most stable chemical with PHI of 52.5 days, followed by monocrotophos (24 days) and carbofuran (20.5 days). The PHIs of profenophos, chlorpyrifos, methomyl and cypermethrin were similar and within the range of 10-13 days. Imidacloprid and λ-cyhalothrin had similar PHI of 4.5 days. Spinosad was the fastest-degrading chemical with PHI of 2 days. The combined bioefficacy and residue dynamics information will support label-claim of these insecticides for the management of thrips in onion, help in scheduling their applications in pest management program as per relative PHIs and minimize the residue accumulations at harvest. The dietary exposure was less than the maximum permissible intake for most of the insecticides on all sampling days except for dimethoate and monocrotophos.

In vivo metabolic fate of [14C]-acetamiprid in six biological compartments of the honeybee, Apis mellifera L

The in vivo metabolism of acetamiprid was studied in the honeybee, Apis mellifera L. The distribution of acetamiprid and its metabolites was monitored over a 72-h period in six biological compartments: head, thorax, abdomen, haemolymph, midgut and rectum. Honeybees were treated orally with 100 microg [14C]-acetamiprid kg(-1) bee, a dose which is about 1500 times lower than the median lethal dose. After 72 h, only 40% of the total radioactivity was eliminated, suggesting that acetamiprid and its metabolites tended to persist in the honeybee. Acetamiprid was rapidly distributed in all compartments and metabolized. Just after administration, radioactivity was mainly localized in the abdomen and subsequently in the rectum. After 72 h, the maximum amount of radioactivity (about 20% of the ingested dose) was detected again in the abdomen, whereas the lowest level of total radioactivity was detected in the haemolymph. Radioactivity in the head did not exceed 7.6% of total ingested radioactivity. More than 50% of acetamiprid was metabolised in less than 30 min, indicating a very short half-life for the compound. During the first hours, acetamiprid was mainly detected in nicotinic acetylcholine receptor-rich tissues: abdomen, thorax and head. Of the seven metabolites detected, the major ones were 6-choronicotinic acid and an unknown metabolite called U1, which was present mainly in the rectum, the thorax and the head. Our results indicate that the low toxicity of acetamiprid may reflect its rapid metabolism.