Fate and disposition of diflubenzuron in rice fields

Laboratory and field investigations were undertaken to determine the fate, disposition, and persistence of the insecticide diflubenzuron in California rice culture. Water solubility was similar in distilled/deionized water (88.8 ± 4.0 μg/L) and rice field water (92.6 ± 3.5 μg/L), while the measured Henry's law constant was 2.34 ± 0.02 × 10−1 Pa.m3/mole. Diflubenzuron was rapidly photodegraded in field water primarily to the more stable chlorophenylurea and difluorobenzoic acid; field water photolysate was equally toxic to Daphnia magna as pure insecticide solutions. Applications to experimental rice field plots resulted in rapid dissipation of diflubenzuron (half-life 27.3 h), nonpersistent sediment residues, and significant partitioning into the surface microlayer.