EFFECTIVENESS OF TERBUTHYLAZINE AND ATRAZINE IN THE CONTROL OF Bidens subalternans IN THREE STAGES OF APPLICATION

The objective was to evaluate the efficacy of terbuthylazine and atrazine doses in controlling greater beggarticks (Bidens subalternans) that are resistant to ALS inhibitors and exhibit resistance to atrazine, at three application times. The treatments were arranged in a 2x6 factorial design, in which two herbicides were used: atrazine and terbuthylazine, and six doses: 0; 375; 750; 1,500; 3,000 and 6,000 g ai ha-1. The application was carried out in three stages of B. subalternans plant development: early post-emergence (2-4 leaves), late post-emergence (6-8 leaves), and pre-emergence. The control of B. subalternans plants was evaluated. Data were analyzed separately for each stage. In early post-emergence, the dose of 375 g ai ha-1 was enough to reach almost 100% control, in which terbuthylazine and atrazine were similar. In late post-emergence, the application of atrazine was effective at a dose of 3,000 g ai ha-1, with 95% control. Terbuthylazine at a dose of 375 g ai ha-1 was effective with 99.8% control. In pre-emergence, atrazine and terbuthylazine were effective in controlling B. subalternans, at doses of 1,500 g ai ha-1 (96% control) and 375 g ai ha-1 (99% control), respectively, evidencing the superiority of terbuthylazine. Keywords: greater beggarticks; triazines; photosystem II inhibitors; pre-emergence; post-emergence.