Use of herbicides to control regrowth plants of Euphorbia heterophylla

Resumo

The control of mature weeds in agriculture demands higher costs and more complex management strategies than the treatment of younger plants. This control is more difficult on regrowth weeds that present morphologic, physiologic, and biochemical characteristics that provide higher tolerance. This study aims to evaluate the control efficiency of different herbicides and associations, in different doses, on regrowth plants of Euphorbia heterophylla in the fall period, after the cultivation of common beans in a second harvest. The experiment was conducted in field conditions in a randomized block design with four repetitions of thirteen treatments: control (without herbicide); glyphosate (868 and 1736 g ha^-1); metsulfuron (1.2 and 2.4 g ha^-1); 2.4-D (335 and 670 g ha^-1); metsulfuron + 2.4-D (1.2 + 335 g ha^-1 and 2.4 + 670 g ha^-1); iodosulfuron (1.75 and 3.5 g ha^-1); triclopyr (48 and 96 g ha-¹). Thirty-five days after the herbicide application, the following characteristics were evaluated: phytotoxicity, plant height, number of seeds per plant, and dry mass. The results demonstrate that the use of glyphosate in both doses tested (868 and 1736 g ha^-1) provides adequate control of regrowth plants of E. heterophylla. The use of metsulfuron + 2.4-D (2.4+670 g ha^-1) stands out as an efficient alternative when is not possible the use of full action herbicides, demonstrating high phytotoxicity (94%) and reduction of dry mass (89%).