Dissipation of captan, boscalid and trifloxystrobin residues in apples of four varieties within 2 months before their harvest

Abstract

Studies on captan, boscalid and trifloxystrobin residues in apples of four varieties treated within 2 months before their harvest were carried out. Just after the application of Captan 80 WG on July 28 at rates 1.9 kg per ha on each of those varieties, the average captan residues were in the range from 3.19 ± 1.01 to 4.76 ± 1.54 mg kg−1, while after the treatment using Bellis 38 WG on August 29, the average boscalid residues ranged from 0.19 to 0.50 mg kg−1. Based on the obtained exponential equations, decay rate constants (k) of captan on the varieties Golden Delicious and Gloster were 0.164 and 0.127 day−1, while on Elise and Gala they were 0.141 and 0.213 day−1. Captan residues, when applied on July 31, within 32–51 days should drop below 0.0051 mg kg−1, while if applied a month later they were still significantly higher than 0.01 mg kg−1. After the application of Bellis 38 WG, carried out just before September 16, the average boscalid residues were 0.25 mg kg−1 (Golden Delicious), 0.36 mg kg−1 (Gloster) and 0.33 mg kg−1 (Elise), and at harvest they were below 0.25 and 0.36 mg kg−1 (Golden Delicious and Gloster), 0.10 mg kg−1 (13 days after last treatment) and below 0.18 mg kg−1 (a week before harvest), and they remained still significantly higher than the residues allowed in products designed for babies and toddlers 0.01 mg kg−1.