Seletividade de herbicidas em espécies de gramas ornamentais

Abstract

The experiment was conducted with the objective of evaluating the selectivity of herbicides, applied in different times, in ornamental turf grasses. The first experiment was conducted in greenhouse conditions in randomized entirely design, with four replications, in a 4 x 5 x 2 factorial scheme. The factors corresponded to the pre-planting application herbicides ( sulfentrazone - 800 g ha -1 , s-metolachlor - 1440 g ha -1 and atrazine - 2000 g ha -1 and control without herbicide application) in five species of turfgrass: Zoysia japonica (emerald) , Axonopus compressus (blanket grass) , Paspalum notatum (bahia grass), Zoysia tenuifolia (no-mow grass) , Stenotaphrum secundatum (sant agostine grass), in sandy loam and clayey texture soils. In the second experiment, the experimental design was completely randomized, with four replications in a 6 x 6 factorial scheme. The factors corresponded to the five post emergence herbicides: atrazine (2000 g ha -1 ), sulfentrazone (800 g ha -1 ), halosulfuron (112.5 g ha -1 ), bentazon (0.72 g ha -1 ) and 2.4 D (670 g ha -1 ) applied on the five grasses, cited above and control without herbicide application. Phytotoxicity evaluations were assessed at at 7, 14, 21, 28 and 35 days after herbicide application. In the case of pre planting herbicides, were not detected any phytotoxicity in the grass species, regardless of soil texture. In the experiment with post-emergent herbicides, the bahia and blanket grass were sensitive to the herbicide atrazine, with 38 and 33% phytotoxicity at 21 DAA. However, the recovery of bahia grass was more effective at 35 DAA. The sulfentrazone was phytotoxic on blanket grass. The herbicides bentazon, 2,4-D and halosulfuron were selective to all species studied.