Fate and disposition of diflubenzuron in rice fields

Abstract

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.

The Sulfoximine Insecticide Sulfoxaflor and Its Photodegradate Demonstrate Acute Toxicity to the Nontarget Invertebrate Species Daphnia magna

“…There was no loss of mobility in any zero-concentration controls for the duration of the study, as shown in Table 4. The literature EC50 values for diflubenzuron and imidacloprid are 5 and 102 000 µg/L, respectively (Mabury and Crosby 1996;Raby et al 2018) In a comparison between the values determined in the present study and those found in the literature, it appears that the current method is under-reporting the EC50 by 33 and 67% for diflubenzuron and imidacloprid, respectively. When this is taken into consideration, the EC50 value for sulfoxaflor still falls below that reported by the manufacturer of >399 000 µg/L (Dow AgroSciences 2014).…”

“…Following a procedure established by Mabury and Crosby (1996) 1-L solutions of sulfoxaflor at a concentration of 250 µg/L in filtered river water were irradiated by simulated sunlight for a period of 1 (t 50% ), 2 (t 25% ), and 3 (t 12.5% ) half-lives, using direct photolysis to produce the sulfoxaflor-OH photolysate. This concentration was selected as approximately one-half the EC50 of sulfoxaflor as determined in the present study.…”

Literature review for candidate chemical control agents for nonnative crayfish

“…Diflubenzuron is registered with EPA as a terrestrial insecticide. Potential data have been reported for guidelines 835.1230-adsorption/desorption (table 2.15; Sundaram and others, 1997), 835.2240-photodegradation in water (Mabury and Crosby, 1996), 835.6200-aquatic (sediment; Mabury and Crosby, 1996), and 875.1100-human applicator dermal exposure (Roitzsch and others 2019). The data gaps for registration includes: 870.6200-acute neurotoxicity, 158.660-nontarget plant protection data, and human exposure (Subpart K), except 875.240-post-application human dermal exposure and 875.2200-post-application human soil residue dissipation, as identified in tables 1-4..…”