Effectiveness and selectivity of herbicides applied under preemergence conditions in weed management for coffee crops

The coffee plant is sensitive to weed competition, which negatively affects its growth and development. Thus, the proper and safe use of herbicides is extremely important for weed management to allow the crop to develop its maximum productive potential. The objective of this study was to evaluate the control efficacy of different herbicides under pre-emergence conditions and assess their selectivity for coffee crops. Two experiments were carried out in the field, in randomized block designs, with four replicates and eight treatments, totaling 32 experimental plots. The treatments were: unweeded control; weeded control; sulfentrazone + diuron 1.4 L ha-1; sulfentrazone + diuron 1.7 L ha-1; sulfentrazone + diuron 2.0 L ha-1; sulfentrazone + diuron with indaziflam 1.4 + 0.15 L ha-1; respectively, indaziflam 0.15 L ha-1; and oxyfluorfen + chlorimuron 3.0 L ha-1 + 0.08 kg ha-1, respectively. The treatments wereapplied prior to the emergence of weeds in a directed spray between the crop rows. Evaluations of weed control in the area, phytotoxicity to the crop, branch length, and internode distance of coffee were conducted at 30, 60, 90, and 120 days after treatment application (DAA). In general, all treatments guaranteed greater than 80% efficacy up to 60 DAA. After this, some treatments suffered reductions in efficacy, and did not guarantee satisfactory control up to 120 DAA. For Digitaria nuda, the most effective treatments were those that contained indaziflam alone or in combination with sulfentrazone + diuron, and oxyfluorfen + chlorimuron for 60 DAA. In both experiments and the two species analyzed, the indaziflam treatments guaranteed efficacy percentages above 80%, even at 120 DAA. All treatments were equally selective for the coffee plants under the conditions evaluated. Key words: Coffea arabica; Chemical control; Phytotoxicity.