Persistence and degradation pattern of chlorothalonil in spinach

With a view to study the dissipation of chlorothalonil in/on spinach, a field experiment was conducted at Indian Institute of Horticultural Research, Bangalore, India. The foliar application of chlorothalonil (Kavach 75% WP) was carried out at 2 concentrations 50g and 100 g a.i. ha-1 in spinach at 45 days after sowing. Samples were drawn at 0 (1hour), 1, 3, 5, 7, 10, 15 and 20 days after spray. Soil samples were also collected on 20thday after application. The initial deposits of chlorothalonil on spinach beet were 111.98 and 192.93 at recommended dose and double the recommended dose of application, respectively. The residues gradually declined and persisted upto15th day at lower and higher dose, respectively. The residues reached below quantitation limit of 0.01 ug g-1on 20thday at recommended and double the recommended dose, respectively. Half life of chlorothalonil on spinach beet was 1.27 and 1.28 days for standard dose and double the standard dose, respectively. Soil samples analysed on the 20thday after last spray revealed residues at below quantitation limit of 0.01 ug g-1 at either dose of application.