CONTROLLING GROWTH OF COMMON CARPETGRASS USING SELECTED PLANT-GROWTH REGULATORS

Field studies were performed on established carpetgrass (Axonopus affi nis Chase) in 1994 and 1995 to evaluate plant growth regulators (PGRs) and application rates. Trinexapac-ethyl (0.48 kg.ha(-1)) improved tur f quality and reduced cumulative vegetative growth (CVG) of unmowed an d mowed plots by 38 % and 46 %, respectively, in 1995, and suppressed seedhead height in unmowed turf by >31% 6 weeks after treatment (WAT) both years. Mefluidide (0.14 and 0.28 kg.ha(-1)) had little effect on carpetgrass. Sulfometuron resulted in unacceptable phytotoxicity (>20% )2 WAT in 1994 and 18% phytotoxicity in 1995, In 1995, sulfometuron re duced mowed carpetgrass CVG 21%, seedhead number 47%, seedhead height 36%, clipping yield 24%, and reduced the number of mowings required. I t also improved unmowed carpetgrass quality at 6 WAT. Sethoxydim (0.11 kg.ha(-1)) suppressed seedhead formation by 60 % and seedhead height by 20 %,and caused moderate phytotoxicity (13%) in 1995, Sethoxydim (0 .22 kg.ha(-1)) was unacceptably phytotoxic (38%) in 1994, but only sli ghtly phytotoxic (7%) in 1995, reduced clipping yields (>24%), and inc reased quality of mowed carpetgrass both years. Fluazasulfuron (0.027 and 0.054 kg.ha(-1)) phytotoxicity ratings were unacceptable at 2 WAT in 1994, but not in 1995, Fluazasulfuron (0.054 kg.ha(-1)) reduced see dhead height by 23 % to 26 % in both years. Early seedhead formation w as suppressed >70 % when applied 2 WAT in 1994, and 43% when applied 6 WAT in 1995, The effects of the chemicals varied with mowing treatmen t and evaluation year. Chemical names used: 4-(cyclopropyl-x-hydroxy-m ethylene)-3,5 dioxo-cyclohexane-carboxylic acid ethyl ester (trinexapa c-ethyl); (trifluoro-methyl)sulfonyl]amino]phenyl]acetamide] (mefluidi de); [methyl rimidinyl)amino]carbonyl]amino]sulfonyl]benzoate)] (sulfo meturon); (2-ethylthio)propyl]-3-hydoxy-2-cyclohexene-1-one) (sethoxyd im); ethoxypyrimidin-2yl)-3-[(3-trifluoromethyl-pyridin 2-yl) sulphony l] urea (fluazasulfuron).