In order to evaluate the development of the grass species Bermuda (Cynodon dactylon), Emerald (Zoysia japonica) and Broadleaf Carpetgrass (Axonopus compressus) submitted to herbicide sub doses and growth regulators under two light conditions, three experiments were conducted in a greenhouse at Paraguaçu Paulista from September to December, 2006. For each grass species, the experimental design used was completely randomized, in a factorial scheme 6 x 2, with four replications, using two growth regulators (trinexapac-ethyl and ethephon), three herbicides applied in sub doses (clethodim, imazethapyr and metsulfuron-methyl), and a check without application. All treatments were evaluated under two light conditions, represented by plastic greenhouse (total light) and plastic greenhouse + shading 50% (partial light).The results obtained at 63 days after application showed that trinexapac-ethyl (250 g ha-1), clethodim (12 g ha-1) and imazethapyr (12 g ha-1) were the best growth regulators for the vegetative development of C. dactylon (65.8, 29.6 and 18.7%), Z. japonica (66.2, 40.7 and 49.7%) and A. compressus (56.5, 10.3 and 17.2%) grasses and for inflorescence emission of C. dactylon (100.0, 95.9 and 89.6%), under high and low luminosity. Ethephon (300 g ha 1) and metsulfuron-methyl (3.6 g ha-1) treatments were found to be the best options for reducing vegetative development (15.5 and 26.7%) and root dry matter (34.7 and 33.9%) of São Carlos grass (A. compressus), compared to trinexapac-ethyl. For C. dactylon and Z. japonica turf grass, under conditions where aesthetics preservation is fundamental, clethodim and imazethapyr may substitute trinexapac-ethyl growth regulator on account of the smaller visual damage in the grass. Further studies with growth regulators and herbicide sub doses must be conducted with other cultivated grasses to enable efficient and safe recommendations, based on scientific information generated from Brazilian conditions.
plant regulator; herbicide; Cynodon dactylon; Zoysia japonica; Axonopus compressus
