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

Abstract

Abstract Achieving effective weed control is crucial for Wisconsin conventional corn growers farming in atrazine prohibition areas. Upon request from our extension clientele, a field study was conducted at Arlington and Brooklyn, WI, in 2021 and 2022 (four site‐years). The study aimed to evaluate the weed control efficacy of comprehensive two‐pass (PRE followed by POST) herbicide program treatments containing products with a wide range of active ingredients and sites of action from various manufacturers without atrazine and glyphosate, in conventional tillage non‐transgenic corn production. Nine and eight out of the 11 two‐pass herbicide programs investigated provided >90% giant foxtail (Setaria faberi Herrm), common ragweed (Ambrosia artemisiifolia L.), velvetleaf (Abutilon theophrasti Medik) and waterhemp [Amaranthus tuberculatus (Moq.) J.D. Sauer] control in 2021, respectively. However, only three treatments provided >90% waterhemp control and the greatest giant foxtail control in 2022 was 79%. Greater end‐of‐season broadleaf and grass weed control was observed in 2021 compared to 2022 due to lower weed pressure and timely early‐season rainfall in 2021. The two‐pass programs, acetochlor/mesotrione fb dicamba/tembotrione (94%–100%) and acetochlor/flumetsulan/clopyralid fb nicosulfuron + dicamba/diflufenzopyr (85%–100%), provided the most consistent broadleaf control across all site‐years. These results demonstrate that a well‐designed and timely deployed two‐pass herbicide program can provide effective control of common broadleaf and grass weeds in conventional corn production assuming moderate weed pressure and timely rainfall for soil residual herbicide activation, otherwise effective weed control, particularly of grass weeds, in the absence of atrazine and glyphosate can be challenging. These results are also translatable to support weed management decisions for glyphosate‐resistant corn hybrids in non‐atrazine prohibition areas.