CONTROL OF Cyperus difformis BY ALS HERBICIDES AND AUXIN MIMICS

Abstract

The occurrence of Cyperus difformis L. biotypes with characteristics of resistance to herbicide application in the rice sector is a worldwide concern. In this sense, the objective was to evaluate the efficiency of the control of C. difformis by acetolactate synthase (ALS) inhibitors and auxin mimic. The experimental design was completely randomized, with four replications, totaling 252 experimental units composed of pots with 12 kilograms of soil and the treatments arranged in a 3x7x2x2 factorial scheme: three herbicides (two ALS inhibitors pyrazosulfuromethyl and bispiribaque-sodium and a mimetic of triclopyr-butotyl auxin); seven doses of the herbicides (0.0x, 0.5x, 1x, 2x, 4x, 8x and 16x the registration dose); two biotypes of C. difformis (Santa Rosa do Sul and Meleiro, Santa Catarina (SC)); and two soil moisture (100% saturated and 5,0 cm water depth). The C. difformis biotype of Meleiro-SC is 8x (320 g. i.a. ha-1) more resistant to the registration dose of bispiribaque-sodium, whereas the biotype of Santa Rosa do Sul-SC is more susceptible, reducing 50% of the dry mass of the aerial part with 0.5x of the registration dose (20 g. i.a. ha-1). Pyrazosulfuromethyl proved to be inefficient in reducing the dry mass of the aerial part in both biotypes. The biotypes C. difformis of Santa Rosa do Sul-SC and Meleiro-SC, in both soil moisture conditions, are susceptible to triclopyr-butotyl, reducing 50% of the dry mass of the aerial part with 0.5x (166 g. i.a. ha-1) the registration dose.