Dissipation of spiromesifen and spiromesifen-enol on tomato fruit, tomato leaf, and soil under field and controlled environmental conditions.

Dissipation of spiromesifen and its metabolite, spiromesifen-enol, on tomato fruit, tomato leaf, and soil was studied in the open field and controlled environmental conditions. Sample preparation was carried out by QuEChERS method and analysis using LC-MS/MS. Method validation for analysis of the compounds was carried out as per "single laboratory method validation guidelines." Method validation studies gave satisfactory recoveries for spiromesifen and spiromesifen-enol (71.59-105.3%) with relative standard deviation (RSD) < 20%. LOD and LOQ of the method were 0.0015 μg mL-1 and 0.005 mg kg-1, respectively. Spiromesifen residues on tomato fruits were 0.855 and 1.545 mg kg-1 in open field and 0.976 and 1.670 mg kg-1 under polyhouse condition, from treatments at the standard and double doses of 125 and 250 g a.i. ha-1, respectively. On tomato leaves, the residues were 5.64 and 8.226 mg kg-1 in open field and 6.874 and 10.187 mg kg-1 in the polyhouse. In soil, the residues were 0.532 and 1.032 mg kg-1 and 0.486 and 0.925 mg kg-1 under open field and polyhouse conditions, respectively. The half-life of degradation of spiromesifen on tomato fruit was 6-6.5 days in the open field and 8.1-9.3 days in the polyhouse. On tomato leaves, it was 7-7.6 and 17.6-18.4 days and in soil 5.6-7.4 and 8.4-9.5 days, respectively. Metabolite, spiromesifen-enol, was not detected in any of the sample throughout the study period. Photodegradation could be the major route for dissipation of spiromesifen in the tomato leaves, whereas in the fruits, it may be the combination of photodegradation and dilution due to fruit growth. The results of the study can be utilized for application of spiromesifen in plant protection of tomato crop under protected environmental conditions.