Herbicide selectivity on forage cactus (Nopalea cochenillifera) (L.) Salm - Dick cv miúda

The objective of this work was to evaluate the herbicide selectivity and efficiency on weed control in forage cactus. The treatments were composed of oxyfluorfen, sulfentrazone, ametrine, hexazinone and the weeded control, with 4 replications. The potential quantum yield of photosystem II (Fv/Fm) was evaluated; phytotoxicity levels; productivity of green and dry mass of the aerial part and efficiency of the products in the control of the weeds. It was observed that there was no change in the potential yield of photosynthesis (Fv/Fm) of forage cactus, the values were between 0.76 and 0.83 quantum-1 electrons, the plants did not show phytotoxicity, only those that received oxyfluorfen with later recovery. The average productivity of plants that received herbicides was similar to the weeded control. The herbicides oxyfluorfen and ametrine were efficient in the first 45 days after application (DAA), hexazinone showed moderate control until 45 DAA, sulfentrazone obtained low control of weeds that appeared in the experimental period. The herbicides were selective for forage cactus, oxyfluorfen, hexazinone and ametrine are efficient in controlling weeds up to 45 DAA.