Terrestrial Environment. 10 Flumioxazin has a mean Koc of 557 L/Kg and is thus considered to have “moderate” soil mobility 12 batch equilibrium studies due to the rapid degradation of flumioxazin in soil and water. Flumioxazin 13 degrades rapidly in aerobic soil (half-time [t1/2] = 11.9 days) and very rapidly in anaerobic aquatic 14 sediment (t1/2 = 4.3 hours) (U.S. EPA 2003). Flumioxazin has two major degradants in the terrestrial 15 environment, 6-amino-7-fluoro-4-(2-propynyl)-2H-1,4-benzoxazin-3(4H)-one (APF) and 3,4,5,6- 18 (MRID 45309201; MRID 45309202). This increases the likelihood that hydrolysis products of 19 flumioxazin will migrate to groundwater. 20 In two soil photolysis studies, flumioxazin degraded rapidly (t1/2 = 3.2 and 8.4 days) (MRIDs 44295038 21 and 44295039). In an aerobic soil metabolism study, flumioxazin degraded with a t1/2 of 11.9 days 22 and produced four minor degradants: THPA; 3,4,5,6-tetrahydrophthalicanhydride (Δ-TPA); 7-fluoro- 25 Based on findings in six field dissipation studies, the major routes of flumioxazin degradation in the 26 environment are hydrolysis, photolysis, and biodegradation of the parent compound (U.S. EPA 27 2003). For five of the six dissipation studies, flumioxazin was broadcast in a single event at an 28 application rate of 42.5 – 45.0 g a.i./acre (0.094-0.099 lbs a.i./acre). In the sixth study, flumioxazin 29 was broadcast twice at a rate of 42 g a.i./acre (0.092 lbs a.i./acre) with a 30-day interval. Although 30 these rates are one-quarter to one-half of the labeled rates of 0.188 and 0.38 lb a.i./acre, this should 31 not affect the identities of the degradants. Calculated field dissipation t1/2 values for flumioxazin 32 were between 4.8 and 42 days. The large range is primarily caused by frequency of rainfall and soil 33 pH, with more frequent rainfall and higher soil pH leading to increased soil dissipation. This is 34 consistent with hydrolysis of flumioxazin. In one of the dissipation studies (MRID 44295047), 35 7-fluoro-6-[(2-carboxyl-1-cyclohexenoyl)amino]-4-(2-propynyl)-1,4-benzoxazin-3-(2H)-one (482-HA) 36 and APF were detected as major degradants and 482-CA and IMOXA were detected as minor 37 degradants. Xxxxxxx et al. (2008) reported DT50 (time required for a 50% reduction in concentration) 38 values of 10.6 –32.1 days and Kd values of 2.54 – 6.51 mg/L for four sites. Additionally, flumioxazin 39 did not xxxxx below 45 cm in any of the locations in this study (Xxxxxxx et al. 2008).
Terrestrial Environment. 11 Indaziflam is marketed as a pre-emergent herbicide that requires “activation” in the soil column by 12 rain fall (minimum 0.25 inches) so that the chemical becomes incorporated into the soil matrix. 13 Manufacturer’s instructions generally instruct users not to reapply the product but every 6 to 12 14 months. For example, Esplanade 200 SC repeated applications must not additively exceed the 15 maximum label rate (10 fl oz per acre) during any 12-month period It is possible that indaziflam can 16 prevent germination of annual grasses for multiple years if the conditions are favorable such as 17 adequate but not excessive rainfall, higher soil organic content and adequate incorporation of the 18 chemical into the soil matrix following application leading to adsorption on the soil particles.
