Chemical control is the main method used for weed management in sugarcane, with herbicides being usually applied in post-emergence. In some cases, serious toxicity is reported following herbicide application. To reduce the problem of injuries caused by herbicides to sugarcane, the doses used may be reduced to below those recommended in the label, with satisfactory control of the weed community still being obtained, when applied under appropriate environmental conditions. This study aimed to evaluate the efficiency and toxicity caused by doses ranging from zero to those recommended in the label of the herbicide mixture {(diuron + hexazinone) + MSMA} applied on the sugarcane variety RB867515, as well as on the weed species Brachiaria brizantha. The experiment was arranged in a completely randomized block design, with four replications. Treatments were allocated in a factorial design (6 x 3), with factor A being the herbicide (0.0, 50.0, 62.5, 75.0, 87.5 and 100.0% of the commercial dose): diuron + hexazinone (1,20 kg ha-1) and MSMA (1,44 kg ha-1), applied in combination; and factor B, the times of application ofthese herbicides, as follows: two to three leaves; four to five leaves and six to seven fully-expanded leaves, corresponding to the two- to four- leaf stages , 6 leaves to one tiller and one to four tillers of the weed species, respectively. At 7, 21, 35, and 49 days after herbicide application, visual analyses of intoxication and control of B. brizantha were carried out, as well as crop yield estimation, 12 months after planting. Considering the situations evaluated, the control of B. brizantha ranged between 50 and 100%, with higher control levels at the higher herbicide doses. The best control of B. brizantha throughout the crop cycle was found to occur when treatments were applied at the two- to- four-leaf stage of the weed species. Toxicity to the crop increased as the doses of {(diuron + hexazinone) + MSMA} increased in all evaluation times, with higher toxicity being observed when the herbicide mixture was applied at the most active growth stages of the crop, leading to lower crop yields.
Saccharum spp; susceptibility; herbicide mixture
