Fate of fipronil and its major metabolites fipronil sulfide (MB 45950), fipronil-desulfinyl (MB 46513) and fipronil sulfone (MB 46136) were studied in/on grape leaves, berries and soil. As initial residue deposits on the leaves the major component was that of fipronil, while all the 3 metabolites were also present. Among metabolites residues of MB 46513 was highest followed by MB 46136 and MB 45950. In leaves fipronil degraded faster than its metabolites. The residues of fipronil in leaves degraded at the half-life of 9.6 and 18.3 days and that of total fipronil (sum of fipronil and its metabolites) at 13.6 and 20 days, from treatment at recommended and double the recommended dose, respectively. At the time of harvest in leaves, grape berries and soil residues of fipronil and all its metabolites were below the quantifiable limit of 0.01 mg kg(-1).
Fluopicolide, a relatively new fungicide is used for control of downy mildew of grape. Persistence study of fluopicolide was carried out on grape berries following treatment of the combination product, fluopicolide 4.44% + fosetyl aluminium 66.7% (Profiler 71.14 WG) at the recommended and double the recommended dose of 2.5 and 5.0 kg ha⁻¹. Four treatment sprays were given at 15 day intervals, starting from 1 month after pruning of the vines. Residues of fluopicolide in grape berries were estimated on 0 (1 h), 1, 3, 5, 7, 10, 15, 20, 25, 30 day and at harvest (64 days after the last spray application). The initial residue deposits of fluopicolide on grape berries were 0.58 and 1.32 mg kg⁻¹ from treatment at the recommended and double dose, respectively. Dissipation of fluopicolide residues was a slow process. After 30 days of treatment, 0.068 and 0.204 mg kg⁻¹ of residues still remained in the berries from treatment at the recommended and double dose, respectively. Fluopicolide residues in grape berries dissipated with the half-life of 10.2 and 12.3 days. Residues in grape berries and soil at harvest were below the quantifiable limit of 0.01 mg kg⁻¹ from both the treatments.
Residue persistence of tebuconazole and quinalphos in immature onion bulb with leaves (spring onion), mature onion bulb and soil was studied following their spray applications 3 times. The applications were untreated control; tebuconazole @ 187.5 and 375 g a.i. ha(-1); quinalphos @ 300 and 600 g a.i. ha(-1). Initial residue deposits of tebuconazole in immature onion bulb with leaves from the two treatments were 0.628 and 1.228 mg kg(-1). The residues of tebuconazole dissipated with the half-life of 5 and 7.7 days. The safe pre-harvest intervals (PHI) for consumption of immature onion bulb with leaves were 16 and 35 days, respectively. Initial residue deposits of quinalphos in immature onion bulb with leaves from the two treatments were 0.864 and 2.283 mg kg(-1). Loss of quinalphos residues from immature onion bulb with leaves was very fast. The residues dissipated with the half-life of 1.7 and 2.6 days and the required PHI was 5 and 11 days, respectively. At harvest mature onion bulbs were free from residues of both tebuconazole and quinalphos.
Supervised field trials following good agricultural practices were conducted at the research farms of four agricultural universities located at four different agroclimatic zones of India to evaluate the persistence and dissipation of flubendiamide and its metabolite, des-iodo flubendiamide, on cabbage. Two spray applications of flubendiamide 480 SC of standard and double dose at the rate of 24 and 48 g a.i. ha(-1) were given to the crop at a 15-day interval, and the residues of flubendiamide 2 h after spray were found in the range of 0.107-0.33 and 0.20-0.49 mg kg(-1) at respective doses. Residue of des-iodo flubendiamide was not detected in any cabbage sample during study period. No residues were found in the soil samples collected from all treated fields after 15 days of application. On the basis of data generated under All India Network Project on Pesticide Residues, a preharvest interval (PHI) of 10 days has been recommended, and the flubendiamide 480 SC has been registered for its use on cabbage by Central Insecticide Board and Registration Committee, Ministry of Agriculture, Government of India. The maximum residue limit (MRL) of flubendiamide on cabbage has been fixed by the Ministry of Health and Family Welfare, Government of India, under Food Safety Standard Authority of India as 0.05 μg/g after its risk assessment.
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