Associations of Herbicides on the Simultaneous Control of Horseweed and Italian Ryegrass

Weed competition negatively affects grain yield on wheat and soybean crops. Due to better practicality and timesaving it is usual the association of broadleaf herbicides with graminicides to control monocot and dicot weeds. However, little is known about the deleterious effects of broadleaf herbicides on graminicides. Thus, the objective of this experiment was to evaluate the effects of simple, double and triple association of broadleaf herbicides with graminicides to control of Italian ryegrass and horseweed. The experiment was conducted into greenhouse on completely randomized experimental design with four replications. The treatments consisted of the graminicides clethodim and clodinafop; the broadleaf herbicides 2,4-D, metsulfuron and saflufenacil and non-selective glyphosate, sprayed isolated and in double and triple association to be compared with a control. The variables evaluated were control (%) at 21 and 28 days after treatments (DAT), and dry weight (g) at 28 DAT. The isolated graminicides and the broadleaf herbicides controlled both Italian ryegrass and horseweed respectively. At the double association of broadleaf with graminicides herbicides, 2,4-D antagonized the effect of clodinafop, and glyphosate mixed with clodinafop decreased the control of the graminicide on Italian ryegrass. At the triple herbicide association, when mixed with glyphosate, metsulfuron decreased the control effect of Italian ryegrass by clethodim. The association of broadleaf herbicides with graminicides is effective on the control of monocot and dicot weeds, but it depends on which herbicide used for the combination. When it is evident the antagonism between broadleaf herbicides and graminicides, the detrimental effects go on grass control.