Biological efficacy of the inhibitor herbicides of acetyl coenzyme a carboxylase and acetolactate synthase and the presence of resistance in echinochloa crus-galli (L.) Beauv

© 2018 Colegio de Postgraduados. In the state of Guanajuato, Mexico, Echinochloa crus-galli is the main weed in wheat and is controlled with inhibitors herbicides of acetyl coenzyme A carboxylase (ACCase) and acetolactate synthetase (ALS), but its control is poor. The objective of this research was to determine the biological efficacy of the herbicides used in wheat and the presence of resistance in E. crus-galli. The experiment was carried out in two phases: 1) biological efficacy and, 2) presence of resistance. To evaluate the biological efficacy in six biotypes (one bioassay per biotype) we applied clodinafop propargil and pinoxaden, ACCase inhibitor herbicides, and sodium flucarbazone and mesosulfuron methyl+iodosulfuron methyl, ALS inhibitor herbicides, in doses of 60, 55, 28 and 15 g of a.i. ha-1, respectively. Each herbicide was one treatment plus a control, and the design was completely randomized with four replications. Regarding the presence of resistance we evaluated the effect of increasing doses of sodium flucarbozone and mesosulfuron methyl + iodosulfuron methyl on the production of dry biomass of the six biotypes, and calculated the resistance index. A completely randomized blocks design was used with four replications. Biological efficacy: the application of the ACCase inhibitor herbicides in the biotypes showed a control of 99 %, and the weight of dry biomass was lower, while the application of the ALS inhibitors caused a control of 42 %, except in one biotype, which was 77 % and it was considered as susceptible. The dry weight of the biomass in some cases was similar to that of the control. Presence of resistance: the resistance index to mesosulfuron methyl + iodosulfuron methyl was greater than 2.0 in two biotypes, while for sodium flucarbazone the resistance indices were lower than 1.35. Therefore, the E. crus-galli resistance to mesosulfuron methyl+iodosulfuron methyl was confirmed.