Management of glyphosate-resistant smooth pigweed and horseweed in burndown, pre-emergence and post-harvest in soybean

Resumo

Background: The advance of smooth pigweed in soybean fields is associated with the evolution of this weed resistance to herbicides. Its presence, together with that of other important weeds, such as horseweed, affect crop’s grain yield.

Objective: Our aim was to evaluate the efficiency of different combinations of herbicides in burndown and pre-emergence for the control of smooth pigweed and horseweed in soybean, and the efficiency of herbicides in off-season management of smooth pigweed.

Methods: The trials were carried out in a complete randomized block design. The visual control variables and plant population of smooth pigweed and horseweed were evaluated, in addition to soybean grain yield. As in off-season, control (%) and dry weight of smooth pigweed plants and phytotoxicity and dry weight of the cover crop ryegrass were evaluated.

Results: Was observed effect of pre-emergent herbicides in the control of smooth pigweed, constituting an indispensable tool in the management of smooth pigweed. The PRE herbicides sulfentrazone+diuron and S-metolachlor+metribuzin combined with carfentrazone+saflufenacil at burndown can be spray. In relation to horseweed, the main effect of all burndown herbicides was observed. In the off-season management of smooth pigweed, the mixtures containing carfentrazone were efficient in the control, and not cause a significant phytotoxicity to the ryegrass.

Conclusions: PRE herbicides are essential in the management of smooth pigweed and horseweed and those that promote better control are the combinations sulfentrazone+diuron and S-metolachlor+metribuzin. The tank mixture with carfentrazone demonstrate some phytotoxicity for the ryegrass crop but control Smooth pigweed.