| Popis: |
St. Augustinegrass [(Stenotaphrum secundatum (Walt.) Kuntz.] is the preferred warm season turfgrass for Florida’s commercial and residential landscapes with an estimated 0.7 million hectares under growth and management. Previous plant growth retardant (PGR) research has demonstrated excellent responses in fine warm season turfgrasses such as bermudagrass [Cynodon dactylon (L.) Pers.] and centipedegrass [Eremochloa ophiruroides (Munro) Hack]. However, limited information is available regarding St. Augustinegrass response to currently labeled or potentially registered PGRs. This two-year study was designed to evaluate St. Augustinegrass root length density (RLD) following PGR application. Treatments included flurprimidol and paclobutrazol at 1.1 kg ha-1, trinexapac-ethyl and mefluidide at 0.28 kg ha-1, and imazapic (formerly AC 263,222) at 0.028 kg ha-1. Root growth was traced at two, four, and six weeks following PGR application on acetate paper attached to the front surface of 15.0 x 50.0 cm clear Plexiglas tubes placed on greenhouse benches at 20° to the vertical. Newman’s random line intersect technique, at an accurate viewing depth of 0.2 cm, was used to quantify RLD. With the exception of imazapic, all PGRs provided RLD values equal to the untreated turfgrass at each of the three biweekly tracing periods during both years. Imazapic inhibited root growth ≈68% for four weeks. However, RLD values for imazapic exceeded the untreated turfgrass at least 50% by week six during both years. Although not significant, paclobutrazol and flurprimidol provided ≈ 11 % and ≈20% higher RLD values at week four in 1994 and 1995, respectively, while trinexapacethyl provided 9% and 43% higher RLD values in 1995 at weeks four and six, respectively. Mefluidide RLD values were similar to the untreated control for the entire rating period of both years. |
