Influence of Dates and Frequency of Drive Treatments On Large Crabgrass Control in Tall Fescue Turf

When postemergence (POST) herbicides are used to control large crabgrass [Digitaria sanguinalis (L.) Scop.] in turfgrasses, it is desirable to maintain a high level of control with minimum number of applications. A field experiment was conducted during 1992 and 1993 to determine the influence of timing and frequency of applications with Drive (quinclorac) on large crabgrass control in tall fescue (Festuca arundinacea Schreb.) turf. Drive (quinclorac) applied as a single application at 0.84 kg/ha (0.75 lb/A) on June 11 controlled 98% large crabgrass throughout the summer in tall fescue turf. The control was consistently higher than when the herbicide was applied earlier (April 12 or May 3) at the same rate. There was no increase in large crabgrass control with multiple Drive (quinclorac) applications, when compared to a single application made on June 11. Drive (quinclorac) applied on June 11 caused a maximum of 35% injury to tall fescue in 1992, but the turfgrass recovered to an acceptable level (<20%) within one week. Maximum turfgrass injury was only 13% when the herbicide was applied at the same date in 1993. Tall fescue treated with multiple applications of Drive (quinclorac) was injured similarly to that reported from a single application, but the turfgrass required a longer recovery period.