Dose-response curves and efficacy of ALS enzyme inhibitors herbicides applied in pre emergence over Amaranthus species

Abstract

Weeds from Amaranthus genus may cause major yield losses in economic crops, including cotton, if not controlled properly. In order to avoid it, it’s necessary correct species identification, besides herbicides suitability and recommended doses. The aim of this study was to develop the dose-response curve of ALS enzyme inhibitors herbicides (trifloxysulfuron-sodium and pyrithiobac-sodium) applied in pre emergence conditions becoming possible to verify the control effectiveness over four important species of Amaranthus (A. hybridus, A. viridis, A. lividus and A. deflexus) as well as the difference in susceptibility between them. For each herbicide, isolated experiments were carried out and studied doses were: 0; 1.8; 3.7; 7.5; 15.0 and 30.0 for trifloxysulfuron-sodium and 0; 35; 70; 140; 280 e 560 for pyrithiobac-sodium, equivalent to 0, ¼, ½, 1, 2 and 4 times recommended rate for clay loam soils. Results indicated that used doses to obtain dose-response curve of trifloxysulfuron-sodium and pyrithiobac-sodium provided control higher than 80% for all Amaranthus species, characterizing the possibility of herbicides application in pre emergence conditions. Besides it, differential susceptibility between Amaranthus species were reported, being A. hybridus and A. lividus the most susceptible species to both herbicides.