The Influence of Plant Growth Regulators on Golf Course Turf

Plant growth regulator (PGR) technology is poorly understood by a majority of golf turf managers. PGRs are touted as tools for reducing mowing, controlling annual bluegrass and increasing green speed. PGRs recommended for use on high quality (or Class A type) turf generally inhibit cell elongation for a period of time (weeks). The process of regulating cell elongation includes the synthesis of giberillic acid (GA). Each PGR affects the synthesis differently. For example, studies have shown that paclobutrazol (Turf Enhancer) and flurprimidol (Cutless) block GA synthesis early in the pathway. This early blockage prevents the creation of the 50 or so GAs necessary for growth. This indiscriminate blockage can result in severe injury under stressful conditions. Also, this explains the morphological effects of Turf Enhancer with regard to widening the blades of bentgrass under regulation. Trinexepac (Primo) blocks the pathway at the very end after the 50 or so GAs are produced but before the important GA, can trigger elongation. In essence, Primo is less physiologically disruptive. PGRs for mowing management could extend the mowing intervals and allow for increased flexibility with staff time. Also, it could reduce wear and tear on mowers, energy consumption and clipping problems. This study is in the third year. The first two seasons investigated clipping reduction and visual quality. Data from these years indicate that regulation greater than 40% significantly reduces turf quality below an acceptable level. Assuming this information, the next two years of research will address morphological and functional parameters such as vertical leaf extension and ability to recover from divot injury.