Concern has been raised that herbicides often used to control perennial ryegrass in warm-season turf could move laterally or “track” and injure neighboring cool-season grasses. Rimsulfuron was applied at 17.5 or 35 g ai/ha to perennial ryegrass in the afternoon. The following morning, while dew was still present, a greens mower was driven through the perennial ryegrass and across the adjacent creeping bentgrass. When evaluated 5, 10, and 25 d after treatment, visible track length and creeping bentgrass injury were greatly reduced by irrigating perennial ryegrass 2 h after treatment or by irrigating both perennial ryegrass and creeping bentgrass prior to simulated mowing. Visible injury of tracked turfgrass persisted for 36 d after treatment when irrigation was not applied and for as few as 5 d when both perennial ryegrass and creeping bentgrass were irrigated. Irrigation had no effect on perennial ryegrass control. Gibberellic acid at 0.12 kg ai/ha and foliar iron at 1.3 kg ai/ha, applied when tracks first appeared, did not improve the recovery of injured creeping bentgrass. Our results suggest that when applying rimsulfuron near susceptible bentgrass, the lowest effective rate should be applied and that the bentgrass should be irrigated at least 2 h after treatment to prevent nontarget injury.

Several field observations and limited research have confirmed that sulfonylurea herbicides commonly used in warm-season turf can laterally relocate via turf equipment and injure neighboring cool-season grasses. This phenomenon is referred to as ‘tracking’ among turf managers and often occurs when mowers traverse treated areas and adjacent creeping bentgrass putting greens, fairways, and tee boxes while foliage is wet with dew. Tracked flazasulfuron and metsulfuron at 9 and 42 g/ha, respectively, caused little injury to creeping bentgrass. Flazasulfuron at 26 and 53 g/ha, and foramsulfuron at 28 g ai/ha tracked while dew was present 20 h after treatment (HAT) resulted in the most noticeable creeping bentgrass injury when tracked. Flazasulfuron at higher rates and foramsulfuron tracked 20 HAT on dew-covered turf reduced turf color compared to nontracked turf. When the mower traversed dry turf at 6 HAT and wet turf at 68 HAT, turf color was reduced less than wet turf tracked 20 HAT. Length of track and creeping bentgrass injury decreased with flazasulfuron rate. When using flazasulfuron at rates between 9 and 53 g/ha, a 1.5- and 4.5-m border, respectively, around creeping bentgrass would eliminate most injury from tracked herbicide.