Exposure of non-target species pesticide via drift is of concern to the United States Environmental Protection Agency (EPA) as evidenced by required buffer zones and language on labels regarding offsite exposure to endangered species. In 2008, flazasulfuron received a conditional registration that specified a 30-m nontreated buffer between treated areas and sensitive plants. This buffer would make most intended uses of flazasulfuron in warm-season turfgrass impossible. Assessment of drift in field conditions is required to replace model-predicted buffer restrictions. Studies were conducted to assess drift of flazasulfuron and a similar herbicide, trifloxysulfuron sodium, in field conditions using conventional turfgrass spray equipment and maximum boom height and minimum droplet size specified on product labels. Herbicides were applied perpendicular to a 6.4 to 9.7 km h −1 wind over 'Riviera' bermudagrass [Cynodon dactylon (L.) Pers.] turf and sentinel corn plants were placed at distances between 0 and 30.5 m downwind. A bioassay based on reduction of corn height growth rate and shoot biomass indicated trifloxysulfuron sodium and flazasulfuron reduced corn growth similarly but the magnitude of these effects were dependent on year. Year dependency was likely associated with differences in corn cultivars between years. Herbicide drift was not detected beyond 4.6 m downwind of any application. Upon reviewing these and other data, EPA approved a label modification for flazasulfuron that reduced the minimum buffer to 7.6 m.

Flazasulfuron is a selective herbicide registered for use in warm-season turfgrass. Concerns have been raised over its mobility in surface water runoff. Studies were conducted in Blacksburg, VA and Charlottesville, VA to evaluate injury to Lolium perenne L. (perennial ryegrass) downslope of plots treated with transition-assisting herbicides, including flazasulfuron, pronamide, and trifloxysulfuron sodium. Flazasulfuron (52 g a.i. ha -1 ) and pronamide (1120 g a.i. ha -1 ) consistently injured L. perenne greater than trifloxysulfuron sodium (17 g a.i. ha -1 ) or lower rates of flazasulfuron (9 and 26 g a.i. ha -1 ). At Charlottesville, soil was more saturated, and a natural rainfall increased the rate of runoff and severity of L. perenne injury below treated plots. At this site, flazasulfuron (52 g a.i. ha -1 ) and pronamide (1120 g a.i. ha -1 ) caused visible injury to L. perenne 10 to 16 m below treated plots. Based on L. perenne injury, flazasulfuron mobility at the rates tested can be considered equivalent or greater than trifloxysulfuron sodium, and equivalent or less than pronamide when subjected to excessive irrigation or rainfall soon after application to saturated soils. Precautions should be taken to avoid application of these herbicides to saturated soils and apply when rainfall is not expected for sufficient time to rinse turfgrass foliage and incorporate nonabsorbed herbicide into soil via light irrigation.