Tessaro, D. creator Benneman, D. creator Perboni, L.T. creator Garcia, J.R. creator Teixeira, M.M. creator Agostinetto, D. creator text periodical abstract or summary bl. continuing eng ABSTRACT Background: The resistance of weeds to herbicides is a problem that has been increasingly studied because of its great importance in agriculture and rapid growth of this phenomenon worldwide. The quick detection of resistant plants is extremely important for resistance management. Weed resistance to herbicides can be detected through field, greenhouse and laboratory tests. A fast way of detecting resistance is using tissue culture method, where is possible to use resistant plant clones and obtain results faster than whole-plant method in greenhouse. Objective: The aims of the research were to detect the resistance of blackjack to herbicides inhibitors of the acetolactate synthase (ALS), addition in vitro cultivation; determine the herbicide concentration of imazethapyr to 95% control of the susceptible plant population; evaluate explants growth; and, determine the herbicide concentration added to the culture medium where is possible to distinguish a resistant from a susceptible plant. Methods: Experiments were carried out in greenhouse and tissue culture laboratory. Screening was performed to select resistant and susceptible biotypes, tests for specie establishment and dose response curves in vitro were made. Results: The herbicide concentration added to the culture medium that provided 95% susceptible biotype control and efficiently differentiated susceptible biotype from resistant one was 0.6μM of imazethapyr. Conclusions: This method helps recommendations of weed management and provides a quick decision to alternative control of this specie, thus avoiding major damage to the crops Keywords: Bidens Pilosa resistance test acetolactate synthase weed. Publicação on-line; 17 ref.; 3 tables; 3 illus.; Summary (En) BIDENS PILOSA ERVA DANINHA HERBICIDA RESISTÊNCIA Londrina-PR : Sociedade Brasileira da Ciência das Plantas Daninhas, 1978 2023-031024 0100-8358; 1806-9681 (on-line) BR2023000838 v. 38 p. 1-9; (2020) https://www.scielo.br/j/pd/a/nL8BGMdp9Gcss5X47gQfwvN/?format=pdf&lang=en https://www.scielo.br/j/pd/a/nL8BGMdp9Gcss5X47gQfwvN/?format=pdf&lang=en BR-BrBNA 230807 20230929085633.0 eng