Total nonstructural carbohydrate storage in creeping bentgrass treated with trinexapac-ethyl

Total nonstructural carbohydrates (TNC) are important for summer recuperation from injury for cool-season turfgrass. The objectives of this study were to determine if trinexapac-ethyl (TE) [4-(cyclopropyl-a-hydroxy-methylene)-3,5- dioxo-cyclohexanecarboxylic acid ethyl ester] affects TNC content and turf quality of a creeping bentgrass at various application frequencies and rates and to investigate any interactions between the effects of TE and traffic treatments on TNC content. Field experiments were conducted in 1995 and 1996 on a mature stand of 'Pennlinks' creeping bentgrass grown on a Flanagan silt loam soil maintained at a height of 1.9 cm. Treatments included a single application (0.28 kg.ha(-1)) or repeat applications at 2 (0.06 kg.ha(-1)) or 4 (one at 0.28 kg.ha(-1) and one at 0.09 kg.ha(-1)) week intervals during the first 8 weeks of each experiment. Treatments were arranged in a strip-plot design with TE applications as whole plots and traffic treatments as strip plots. Traffic treatments began at 2 weeks and 2 days after initial applications in 1995 and 1996, respectively and continued until the last evaluation date. Traffic treatments consisted of 4 passes of a 102.2 kg smooth roller, 2 days.week(-1) in 1995 and 8 passes daily in 1996. A single aqueous extraction method was used for quantification of glucose, fructose, sucrose, and fructan. TNC was the total of all analyzed fractions. Single applications of TE at 0.28 kg.ha(-1) significantly reduced turf quality for 4 weeks in both experiments. Sequential applications of TE at 0.06 kg.ha(-1) exhibited reduced quality compared to the control at 4 and 8 weeks in 1995 and 2 weeks in 1996. When TE was applied once at 0.28 kg.ha(-1), there was a significant reduction in TNC from 4 to 8 weeks after treatment. In 1996 when TE applications were repeated at 2 and 4 week intervals at 0.06 and 0.09 kg.ha(-1), a reduction of TNC from week 4 to week 14 was observed. After 14 weeks the TNC content showed incremental increases. There was no interaction effect between traffic treatments and TE applications in the verdure TNC in either year. In 1996, verdure TNC content was 6% to 17% lower in plots receiving traffic from weeks 4 to 18. These results suggest that high rates of TE, either sequential or single applications, might reduce turf quality or carbohydrate content. While this study has not examined if this is detrimental, multiple TE applications at low rates may minimize any TNC reduction while providing effective growth suppression for extended periods.