Herbicide alternative for Conyza sumatrensis control in pre-planting in no-till soybeans

BackgroundIn the last two decades, herbicide-resistant biotypes of Conyza bonariensis, Conyza canadensis, and Conyza sumatrensis were identified. Objective: To evaluate herbicide alternatives for the control of C. sumatrensis to replace simplified management at soybean pre-sowing in the no-till system and assess the potential herbicide injury to soybeans.MethodsFour experiments were conducted in Palotina, PR, to evaluate alternative managements to the herbicides commonly used in C. sumatrensis , such as synthetic auxins, pre-emergent, and burndown herbicides. All consisted of applications in pre-sowing of soybeans and weed control evaluation. Experiments I and II included evaluations during the crop, such as injury and soybean yield. In all experiments, a randomized block design was used, with four repetitions.ResultsThe treatments with sequential applications were more effective in controlling C. sumatrensis . Triclopyr and dicamba were more effective than 2,4-D.ConclusionsDicamba was the most effective synthetic auxins when applied only with glyphosate, without sequential. With sequential glufosinate, dicamba, and triclopyr application showed the highest efficacy. Glufosinate showed better control when applied sequentially compared to saflufenacil. Pre-emergent herbicides were effective only if combined with dicamba in the first application or with sequential glufosinate. Pre-emergent, synthetic auxins, and burndown herbicides were shown to be potentially selective for soybeans.