Behaviour and risk assessment of fluopyram and its metabolite in cucumber (Cucumis sativus) fruit and in soil.

A field experiment was conducted to estimate residue persistence of fluopyram and its metabolite benzamide in cucumber fruits and soil and their risk assessment in humans and soil environment. Fluopyram (Kafka, 400 SC) was applied as soil drench twice at the interval of 15 days at the rate of 250 (standard dose) and 500 (double dose) g a.i. ha-1 (active ingredient per hectare). Cucumber fruits were collected at 0 (1 h), 1, 3, 5, 7, 10, 15, 20, 30, 40 and 50 days after second application. Soil samples were collected on 15th day after second application. Drench application resulted in detection of residues on the third day in standard dose at the levels of 0.056 mg kg-1 in cucumber fruit. The residue level increased until 20 days reaching 0.092 mg kg-1 followed by decrease to 0.068 mg kg-1 on 30th day after application. In double dose, the residues started accumulating from 0 day with initial levels of 0.093 mg kg-1 and persisted until 30th day. The levels varied between 0.123 and 0.184 mg kg-1 until 15th day of application followed by decrease to 0.127 mg kg-1 by 30th day. The residues reached below determination level (< 0.05 mg kg-1) on 40th day in both the doses after second application. The residue of metabolite benzamide was below determination level (< 0.05 mg kg-1) at both the doses. Hazard quotient (HQ) for residues levels at 15th and 30th day was less than one (HQ < 1). Hence, a pre-harvest interval of 15 days is suggested. Present data can be used to establish maximum residue limit (MRL) in India. The residue of fluopyram in soil on 15th day and the data on soil adsorption coefficient of fluopyram from literature suggests moderate mobility of fluopyram in soil. However, residues of metabolite of benzamide were not detected in soil. Further studies on translocation of fluopyram in soil over the time can be conducted for better understanding of environmental risk. To our knowledge, this is the first report on residue levels of fluopyram in any crop when applied as soil drench.