Kentucky State University
Half-lives of Endosulfan Isomers on Field Treated Vegetables
Institution
Kentucky State University
Faculty Advisor/ Mentor
George Antonious; Tejinder Kochhar
Abstract
The environmental fate of field-applied synthetic pesticides has been under investigation for a number of years. Endosulfan 3 EC, a mixture of α- and β-stereo isomers, was sprayed on fieldgrown pepper and melon plants at the recommended rate of 0.44 kg A.I. acre-1. Plant tissue samples (leaves and fruits) were collected 1 h to 30 days following spraying and analyzed for endosulfan isomers. Analysis of samples was accomplished using a gas chromatograph (GC) equipped with a mass detector in total ion mode. The results indicated the formation of endosulfan sulfate as the major metabolite of endosulfan sulfite and the relatively higher persistence of the β-isomer as compared to the α-isomer. The initial total residues (α- and β- isomers plus endosulfan sulfate) were higher on leaves than on fruits. On pepper and melon fruits, the α-isomer, which is the more toxic to mammals, dissipated faster (T1/2 = 1.22 and 0.95 d, respectively) than the less toxic β-isomer (T1/2 = 3.0 and 2.5 d, respectively). These results confirm the greater loss of the α-isomer compared to the β-isomer, which could ultimately impact endosulfan dissipation in the environment. The higher initial residues of endosulfan on pepper leaves should be considered of great importance for timing field operations and the safe entry of harvesters due to the high mammalian toxicity of endosulfan. Endosulfan residues on treated pepper and melon fruits might exceed the tolerance level of 2 mg kg-1 under intensive agricultural use where endosulfan is recommended on a two-week schedule for control of many vegetable insects.
Half-lives of Endosulfan Isomers on Field Treated Vegetables
The environmental fate of field-applied synthetic pesticides has been under investigation for a number of years. Endosulfan 3 EC, a mixture of α- and β-stereo isomers, was sprayed on fieldgrown pepper and melon plants at the recommended rate of 0.44 kg A.I. acre-1. Plant tissue samples (leaves and fruits) were collected 1 h to 30 days following spraying and analyzed for endosulfan isomers. Analysis of samples was accomplished using a gas chromatograph (GC) equipped with a mass detector in total ion mode. The results indicated the formation of endosulfan sulfate as the major metabolite of endosulfan sulfite and the relatively higher persistence of the β-isomer as compared to the α-isomer. The initial total residues (α- and β- isomers plus endosulfan sulfate) were higher on leaves than on fruits. On pepper and melon fruits, the α-isomer, which is the more toxic to mammals, dissipated faster (T1/2 = 1.22 and 0.95 d, respectively) than the less toxic β-isomer (T1/2 = 3.0 and 2.5 d, respectively). These results confirm the greater loss of the α-isomer compared to the β-isomer, which could ultimately impact endosulfan dissipation in the environment. The higher initial residues of endosulfan on pepper leaves should be considered of great importance for timing field operations and the safe entry of harvesters due to the high mammalian toxicity of endosulfan. Endosulfan residues on treated pepper and melon fruits might exceed the tolerance level of 2 mg kg-1 under intensive agricultural use where endosulfan is recommended on a two-week schedule for control of many vegetable insects.