The occurrence of dicotyledonous weeds has limited the increase of the area of sunflower cultivation in Brazil, due to their impact on crop yield. This is a result of a shortage of products registered for the crop with broad-spectrum control. Thus, two experiments were installed to evaluate the efficacy and selectivity of the imidazolinone herbicides applied on post-emergence dicotyledonous weeds in Clearfield? sunflower crop. The experiments were conducted under field conditions at the district of Iguatemi, Maringá-PR, Brazil. Treatments consisted of two controls without herbicide application, one with weeds and the other weed-free, with sulfentrazone (200,00 g ha-1) applied preemergence and imazapic + imazapyr applied post emergence, at doses of [36.75 +12.25] [52.5 +17.5], [12.25 +36.75] [17.5 +52.5] g ha-1. The control of Euphorbia heterophylla, Conyza bonariensis, Raphanus raphanistrum, Bidens pilosa, Ipomoea grandifolia and Portulaca oleracea was evaluated. Evaluation of toxicity of the Clearfield sunflower® was also carried out, besides crop stand and yield in kg ha-1. Based on the results, it was concluded that the use of the Clearfield® system proved to be a very good option for areas with dicotyledonous weeds, allowing the application of ALS-inhibiting herbicides. In addition, the weed controls obtained ranged from fair to excellent, causing no injuries to the crop and maintaining the initial plant stand and yield.
imazapic; imazapyr; selectivity
