Dissipation of field-applied difenoconazole, imidacloprid, pyraclostrobin and spinosad on Clementine mandarins

The dissipation of field-applied difenoconazole, imidacloprid, pyraclostrobin and spinosad on Clementine mandarins (Citrus clementina Hort. ex Tan.) under controlled conditions throughout the citrus production chain was assessed. At harvest, 42 days after application, the dissipation of these pesticides were 80, 92, and 48% for difenoconazole, imidacloprid, pyraclostrobin, respectively, and spinosad was below the level of detectability. At day 28 after application, spinosad was no longer detected. The model equations that best describe the dissipation curves of these pesticides on Clementine mandarins showed different patterns. Their half-life on Clementine, calculated by the best-fitted experimental data, were 19.2 day (1st-order model) for difenoconazole, 4.1 day (Root Factor (RF) 1st-order model) for imidacloprid, 39.8 day (2nd-order model) for pyraclostrobin and 5.8 day (1st-order model) for spinosad. These results are the first record of pyraclostrobin persistence on mandarins, showing a longer half-life in this matrix than those reported for any other fruit. The treated fruit were harvested and submitted to the usual postharvest treatments: - first, a hypochlorite drenching was performed; - as a second step, imazalil and wax were applied, - and then the mandarins were stored at 4?C. After 32 days, cold storage caused no significant effects on the residue levels of the four pesticides compared with those determined on freshly harvested mandarins. All residues were below their Codex and European Union (EU) maximum residue limit (MRL) for mandarin since the spray application day.FigureDifenoconazole, imidacloprid and pyraclostrobin residues on Clementine at harvest, after the postharvest packing line and after 32 d of cold storage. For difenoconazole and pyraclostrobin, no significant differences were detected between the pesticide levels. For imidacloprid residue concentration at the end of the postharvest period differed significantly from the residue level determined at harvest (Student t-test, ? = 0.05). SourceDissipation of Pre-Harvest Pesticides on ?Clementine? Mandarins after Open Field Application, and Their Persistence When Stored under Conventional Postharvest ConditionsNatalia Besil 1, Ver?nica Cesio 2, Eleana Luque 3, Pedro Pintos 3, Fernando Rivas 3 and?Horacio Heinzen 21 -?Grupo de An?lisis de Contaminantes Trazas (GACT), Departamento de Qu?mica del Litoral, Facultad de Qu?mica, CENUR Litoral Norte, UdelaR, Paysand? 60000, Uruguay2 -?Grupo de An?lisis de Contaminantes Trazas (GACT), C?tedra de Farmacognosia y Productos Naturales, Departamento de Qu?mica Org?nica, Facultad de Qu?mica, UdelaR, Montevideo 11800, Uruguay3 -?Programa Nacional de Investigaci?n Citr?cola, Instituto Nacional de Investigaci?n Agropecuaria INIA, Estaci?n Experimental Salto Grande, Camino al Terrible s/n, Salto 50000, UruguayHorticulturae 2018, 4(4), 55 ?