Weed Control J 2025; 24: e202500825

Research Article

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

DOI: 10.7824/wcj.2025;24:00825

Abstract:

Background:

The advance of smooth pigweed and fleabane in soybean-ryegrass systems is associated with the evolution of weed resistance.

Objective:

Evaluate combinations of herbicides in burndown and pre-emergence for the control of smooth pigweed and fleabane in soybean, and the efficacy of herbicides in off-season management of smooth pigweed in ryegrass.

Methods:

Two field trials carried out in a complete randomized block design with four blocks. The first trial tested burndown (carfentrazone, carfentrazone+saflufenacil, carfentrazone+diquat, and diquat) and pre-emergent (PRE) herbicides (sulfentrazone+diuron, S-metolachlor, flumioxazin+imazethapyr, S-metolachlor+metrobuzin, and without PRE. The second trial tested rates and tank mixes of herbicides 2,4-D, carfentrazone, metsulfuron and saflufenacil)on ryegrass at post-harvest soybean. The control and population of smooth pigweed and fleabane were evaluated, in addition to soybean yield. As in off-season, control (%) and dry weight of smooth pigweed plants, and phytotoxicity and dry weight of ryegrass were evaluated.

Results:

The PRE sulfentrazone+diuron and S-metolachlor+metribuzin combined with carfentrazone+saflufenacil at burndown can be sprayed with selectivity and control efficacy to smooth pigweed and fleabane. In relation to fleabane the carfentrazone applied alone had lesser control, regardless of any pre-emergent herbicides. In the off-season management, the mixtures containing carfentrazone were efficient in the control, and not cause a significant phytotoxicity to ryegrass.

Conclusions:

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