Tests to verify resistance (R) vary according to time of execution and degree of complexity, and the efficacy of rapid and simple methods to confirm weed resistance to herbicides must be determined. Two experiments were simultaneously carried out in a completely randomized design, under laboratory conditions, by submerging leaves of E. heterophylla susceptible and with multiple resistance to ALS-and PPO inhibitors in herbicide solutions. The aerial part of the plants was submerged in herbicide solution at different concentrations of imazethapyr, imazapyr, and nicosulfuron (ALS inhibitors), and fomesafen, lactofen and carfentrazone (PPO inhibitors). S biotype control increased with time and commercial ratings of ALS and PROTOX inhibitors had an effective control. The R biotype showed different levels of resistance as a function of the herbicide and variable evaluated. The results confirm that leaf immersion technique is adequate to discriminate S biotypes from those with multiple resistance to ALS and PPO inhibitors. The technique proved to be quick enough for early detection of resistance, allowing the adoption of measures to deal with resistance during the same season.
wild poinsettia; dose-response curves; multiple resistance; weed resistance to herbicides
