Identification and management of Chloris polydactyla biotypes with resistance or differential susceptibility to glyphosate in the state of Paraná

Abstract

The emergence of resistant weeds has increased costs and affected the production of crops for weed interference with cultivation and loss of effectiveness of herbicides widely used with large spectrums control and low cost, such as glyphosate. Thus, the study aimed to identify populations of C. polydactyla resistant or differential susceptibility to the herbicide glyphosate, at the State of Paraná, and establish its alternative control. It was collected biotypes suspected resistance in municipalities located in the West, Midwest and Northwest regions of state. Installed a test of resistant populations screening, in a completely randomized design with treatments 0, 450, 650 and 900 g a.e. ha^-1 glyphosate herbicide, with 4 repetitions, assessing visual control with 7, 14 and 21 days after application − DAA and accumulation of fresh matter. Determined the alternative control by plants from different populations subjected to treatments: witness; glyphosate; quizalofop; haloxyfop; tepraloxydim, clethodim and the combination of these graminicides to glyphosate, by evaluating visual control at 14, 21 and 28 DAA and reduction of fresh matter. The state of Paraná has populations of C. polydactyla that require high doses of glyphosate to decrease its fresh weight or achieve adequate levels of control, and an alert to the emergence of resistant populations. The study populations of this species were easily controlled with the association of glyphosate and clethodim, in a commercial dose. It is extremely important to rotate active ingredients and mechanisms of action on the rural property due to specific characteristics of the target population.