A trial was carried out in a greenhouse to evaluate the efficacy of sequential applications of low rates of fomesafen through sprinkler irrigation water (herbigation) for Bidens pilosa control. The following 4x3x2+3 factorial scheme was used: rates of fomesafen (50, 100, 150, and 200 g ha-1 ), sequence of days after emergence (DAE) when herbicide was applied (714-21, 14-21-28, and 21-28-35 DAE), application methods (spray and herbigation), and three untreated controls (one for each weed age). Weed ages were obtained by sowing at seven day intervals. A completely randomized design with three replications was used. The experimental unit consisted of a pot with 12 liters of soil, where fifty seeds were sown. The first, second, and third applications in each sequence of days consisted of ¼, ¼ and ½ of the total rate, respectively. A CO2 spray was used to apply the herbicide in 200 L ha-1 of water. For herbigation, a volume of 4.52 mm (45,300 L ha-1 ) of water was applied using an irrigation simulator. Spraying provided excellent weed control at the rates of 100, 150, and 200 g ha-1 , regardless of weed ages. Sequential applications using sprinkler irrigation water proved to be inefficient.
herbigation; irrigation simulator; low rates
