Control of broadleave and grass weeds in Saccharum officinarum with the use of pre-emergence herbicides

In order to identify combinations of effective preemergent herbicides for weeds in sugarcane, an experiment was conducted at the Agricultural School of Concepción; Concepción, Paraguay. The experimental model was subdivided plots, with two factors: A1 without herbicide for broadleaf weeds, A2 diuron (dose 3 t ha-1), A3 atrazine (dose 4 kg ha-1), A4 sulfentrazone (dose 1.2 t ha-1) and B1 without herbicide for weeds, B2 trifluralin (dose 3 l ha-1), B3 acetochlor (dose 1 l ha-1), forming twelve treatments with three repetitions. They were applied in preemergence, where the evaluations were from 20 to 41 days after application (DDA), for: degree of control, residual effect and control of predominant weeds. The combination of diuron and acetochlor, produced high weed control (more 90% up to 41 days DDA), being superior to the other treatments. Sida spp was better controlled with diuron; whereas Mollugo verticillata was effectively controlled with most combinations; Ipomoea nil was more sensitive to sulfentrazone, while; Cenchrus echinatus was effectively controlled, with the combination of diuron plus acetochlor. It is concluded that with the combination of diuron and acetochlor, a large variety of weeds was controlled and the highest residual effect was recorded. In addition, atrazine combined with graminicides (trifluralin or acetochlor) or diuron with acetochlor, provided total control of weeds. It is recommended: for Sida spp. diuron with acetochlor or atrazine. For Mollugo verticillata, sulfentrazone alone or combined with graminicides. Ipomoea nil, sulfentrazone. Cenchrus echinatus, diuron and acetochlor combined. Key words: Saccharum officinarum, weeds, preemergence herbicides.