Two trials evaluated corn toxicity and weed control efficacy of the herbicides atrazine, foramsulfuron, and iodosulfuron and the insecticide chlorpyriphos applied at postemergence alone or in mixture. A randomized complete block design was used with four replications. In the first trial, the treatments (weed free throughout cultivation) were: atrazine (3000g ha-1 of a.i.); atrazine + clorpyriphos (3000 + 225g ha-1 of a.i.), atrazine + foramsulfuron + iodosulfuron + chlorpyriphos (2,250 + 15 + 1+ 225; 1,500 + 22.5 + 1.5 + 225 and 750 + 30 + 2 + 225 g ha-1 of a.i.); foramsulfuron+ iodosulfuron (45 + 3 g ha-1 of a.i.); foramsulfuron + iodosulfuron + chlorpyriphos (45 + 3 + 225 g ha¹ of a.i.), and a check without herbicides. In the second trial, the same treatments were used, except for atrazine + foramsulfuron + iodosulfuron + chlorpyriphos (750 + 30 + 2 + 225 g ha-1 of a.i.), besides the same treatments above without weed cultivation. AG 3010 cultivar, a short-cycle double hybrid, tolerant to ALS herbicides, was used. During the 2002/2003 agricultural season, corn toxicity and grain yield were evaluated, while during 2003/2004 ,weed control efficacy was also evaluated. Atrazine alone or mixed with chlorpyriphos did not cause any toxicity to the corn plants. Chlorpiryphos + foramsulfuron and iodosulfuron association can increase corn plant injury. The inclusion of atrazine concomitant to foramsulfuron and iodosulfuron reduction allowed partial reduction of corn plant injury, maintaining BRAPL control and enhancing the level of EPHHL control.
synergism; herbicide mixtures; ALS-inhibitors; FSII-inhibitors; grain yield
