ABSTRACT
In order to select products for controlling brachiaria-grass seed-borne fungi and to verify the influence of storage period of treated seeds on the action of these products, 4 laboratory and 4 greenhouse experiments were carried out in São Paulo, Brazil, in 1999 and 2000, with seeds of Brachiaria decumbens treated with the following fungicides, at the indicated doses/100 kg of seeds: quintozene 750 PM (250 g), thiram 500 SC (300 mL), carboxin + thiram 200 SC (300 mL), thiram 350 SC+ thiabendazole 85 SC (200 mL), captan 750 TS (200 g), difenoconazole 150 SC (100 mL) and thiabendazole 485 SC (40 mL). After treatment the seeds were kept in paper sacks and stored at room temperature. Experiments entirely randomized with 8 treatments and 4 replications were carried out periodically, soon after treatment, 3, 6 and 12 months later, in order to evaluate the presence of seed-borne fungi, emergence and seedling symptoms. Seed health tests performed by the blotter method showed the presence of Phoma sp., Exserohilum spp., Fusarium spp. and Curvularia spp., besides saprophytic fungi. Factorial analisis showed significant effects for fungicide treatments and for storage periods, on emergence. After 6 months of storage, emergence was statistically superior to the control in the treatments with thiram + thiabendazole, thiram and carboxin + thiram. At this time, seedlings symptoms were registered in all treatments while they were observed only in the control after 12 months. In 2001/02 the following products, at the indicated doses/100 kg of seeds were evaluated in B. brizantha seed treatment: carbendazin 150 SC + thiram 350 SC (200 mL), fipronil 250 FS (150 mL), (carbendazin 150 SC + thiram 350 SC) + fipronil 250 FS (100 + 100) mL, carboxin + thiram 200 SC (250 mL), carboxin + thiram 200 SC (300 mL), difenoconazole 150 SC (100 mL), thiram 500 SC (300 mL), captan 750 TS (200 g) and tolylfluanid 500 PM (150 g). Evaluation was made by means of 3 experiments, 1 in the laboratory and 1 in the greenhouse (São Paulo, SP, Brazil), entirely randomized and 1 in the field, in randomized blocks, all with 10 treatments and 4 replications. Statistical analisis of data obtained was made by variance applying tests F and Tukey at 5% of probability. Although emergence indices were higher than the ones from the control in most treatments, both in greenhouse as well as in the field, differences were not statistical significant. The same occurred for biomass production. The following products, in decreasing order of number of fungi genera controlled by them in the seeds, are listed: carbendazin + thiram, thiram e captan; (carbendazin + thiram) + fipronil; carboxin + thiram (250 and 300 mL) and tolylfluanid; difenoconazole.
KEY WORDS:
Seeds; chemist control; Brachiaria decumbens; Brachiaria brizantha.