Evaluating a premix of glufosinate/quizalofop (Zalo) for control of volunteer corn in corn resistant to aryloxyphenoxypropionates

Nebraska has significant acreage under continuous corn production in which managing volunteer corn remains a persistent challenge for growers. A new premix of glufosinate/quizalofop (Zalo; AMVAC, Newport Beach, CA) was recently registered for weed control in glufosinate-resistant canola, cotton, and soybean. The objectives of this study were to 1) compare glufosinate/quizalofop with quizalofop (Assure II; AMVAC) applied at the V3 or V6 growth stages to control glufosinate/glyphosate-resistant volunteer corn in corn that is resistant to aryloxyphenoxypropionates (Enlist corn); and 2) evaluate interactions with 2,4-D and their effects on volunteer corn density, biomass, and corn yield. Field experiments were conducted in 2023 and 2024 near Clay Center, Nebraska (3 site-years) and in 2024 near Rosemount, Minnesota (1 site-year). Glufosinate/quizalofop applied at 706 or 948 g ai ha-1 provided 98% to 99% control of volunteer corn and reductions in density and biomass when assessed 28 d after application (DAA), regardless of volunteer corn density and planted corn growth stage at herbicide application, and these outcomes were comparable to those when quizalofop was applied at 65 or 86 g ai ha-1. When the lower rate of glufosinate/quizalofop (706 g ai ha-1) was mixed with 2,4-D (1,064 g ae ha-1), volunteer corn control ranged from 84% to 92% at 14 DAA in 2 site-years. Volunteer corn control improved to ≥96% by 28 DAA or when the higher rate of glufosinate/quizalofop (948 g ai ha-1) was mixed with 2,4-D and assessed at 14 DAA. Enlist corn yield increased in the plots that were sprayed with herbicides compared with nontreated control plots, with no difference among herbicide programs, and yield was comparable to that of the weed-free-treated plots. The results of this study indicate that glufosinate/quizalofop could provide an effective postemergence herbicide option for managing glufosinate/glyphosate-resistant volunteer corn, pending its registration for use on Enlist corn.