This work evaluated the herbicides selectivity acetolactate synthase inhibitors and photosynthetic II applied in post- emergency in palisadegrass (Brachiaria brizantha cv. Marandu) and signalgrass (Brachiaria decumbens cv. Basilisk) plants in field conditions and their effect in seed quality. Treatments tested in g ha-1 were: imazethapyr at 100, chlorimuron-ethyl at 15, nicosulfuron at 50, bentazon at 720, atrazine at 3.000, and control plot. Two field trials were set up on complete randomized block design with four replicates; laboratory studies were carried out in a complete randomized design, with 16 repetitions. All the herbicides showed some visual effect of phytotoxicity in both evaluated cultivars. Nicosulfuron showed the highest visual damages in the cultivars. Dry mass production in the initial growth stage of B. brizantha decreased with application of nicosulfuron and atrazine; dry mass production of B. decumbens was reduced just by the nicosulfuron herbicide. Seed quality of both cultivars was affect by nicosulfuron herbicide only, which induced the seed dormancy of B. decumbens and decreased the normal seed percentage and, like the atrazine, increased the dead seeds.
Brachiaria decumbens; Brachiaria brizantha; pasture; seed production; toxicity
