Preemergence herbicide premixes reduce the risk of soil residual weed control failure in corn

Abstract

Widespread occurrence of herbicide-resistant weeds and more variable weather conditions across the US has made weed control in many crops more challenging. Preemergence (PRE) herbicides with soil residual activity have resurged as the foundation for early-season weed control in many crops. Field experiments were conducted at Janesville and Lancaster, WI in 2021 and 2022 (4 site-years) to evaluate the weed control efficacy of solo (single site of action [SOA]) and premix (two or more SOAs) PRE herbicides in conventional tillage corn. Treatments consisted of 18 PRE herbicides plus a non-treated check. At Janesville-2021, S-metolachlor + bicyclopyrone + mesotrione, atrazine + S-metolachlor + bicyclopyrone + mesotrione, and clopyralid + acetochlor + mesotrione provided >72% giant ragweed control. At Janesville-2022, none of the PRE herbicides evaluated provided >70% giant ragweed control due to the high giant ragweed density and the lack of timely rainfall. At Lancaster-2021, atrazine, dicamba, and flumetsulam + clopyralid provided <45% waterhemp control, but the remaining treatments provided >90% control. At Lancaster-2022, the efficacy of some PRE herbicides was reduced due to the high waterhemp density; however, most herbicides provided >75% control. At Lancaster-2021 and 2022, only dicamba and S-metolachlor did not provide >75% common lambsquarters control. PRE herbicides containing SOA group 15 provided >75% control of giant foxtail. Across weed species, PRE herbicides with two (78%) and three (81%) SOAs provided higher weed control than PRE herbicides with a single SOA (68%), indicating that at least two SOAs PRE result in better early-season weed control. The efficacy of the PRE herbicide treatments evaluated herein varied according to the soil seed bank weed community composition and environmental conditions (i.e., rainfall following application), but the premixes were a more reliable option to improve early-season weed control in conventional tillage corn.

Evaluating cover crop tolerance to corn residual herbicides using field-treated soil in greenhouse bioassay

“…A field experiment was conducted in 2021 and 2022 at the Rock County Farm, Janesville, WI (42.43°N, 89.01°W), and the University of Wisconsin–Madison Lancaster Agricultural Research Station, Lancaster, WI (42.83°N, 90.76°W), to evaluate weed control in corn with multiple soil residual herbicides applied PRE. (For more information about the field experiment and weed control results, see Silva et al [2023]. ) Briefly, soil properties, corn hybrids, and seeding rates for each location are summarized in Table 1.…”

“…Although the cover crops tended to be more sensitive to the premixes with multiple SOAs than with a single SOA (Figure 4), premixes with at least two SOAs are necessary to improve weed control success (Silva et al 2023). In this case, the selection of cover crop species can be more restricted.…”

Evaluation of two‐pass herbicide programs for broad‐spectrum weed control in conventional tillage non‐transgenic corn production in Wisconsin atrazine prohibition areas

“…Success of the selected herbicide program is often dependent on weed community composition and environmental conditions during and following applications (Qasem, 2011;Riethmuller-Haage et al, 2007). Adequate rainfall within 7-14 days following PRE application is necessary for the herbicide incorporation into the soil and availability in soil water solution for uptake by emerging weeds (Chomas & Kells, 2004;Silva et al, 2023;Stewart et al, 2012). Landau et al (2021) reported that 50-100 mm cumulative precipitation within the first 15 days of PRE herbicide application is ideal to activate and prevent losses in PRE herbicide efficacy; however, this range may vary depending on the specific herbicide, soil chemo-physical characteristics, and weed species composition (Klipcan, 2017;Stewart et al, 2012).…”

“…In the present study, two-pass programs #2, acetochlor/mesotrione fb dicamba/tembotrione (95%−100%) and #6, acetochlor/flumetsulan/clopyralid fb nicosulfuron + dicamba/diflufenzopyr (85%−100%) provided the most consistent broadleaf control. Herbicide programs with multiple diverse sites of action are recommended to minimize the risk of weed control failure and to reduce the selection intensity for further evolution of herbicide-resistant weed species (Norsworthy et al, 2012;Silva et al, 2023;Striegel et al, 2021). However, chemical weed management efficacy is associated with weed community composition and environmental conditions.…”