The Evaluation of HPPD-Inhibitors for Full-Season Control of Morningglory (Ipomoea) Species in Corn (Zea mays L.)

Abstract

Several HPPD (4-phenylhydroxypyruvate dioxygenase) products are currently available in corn including standalone HPPD products and products with multiple mechanisms of action (MOA). Some of these are combination products but have a common HPPD-inhibitor MOA to control broadleaf and grass weeds, yet none have been evaluated in a comprehensive side-by-side comparison to evaluate the differences between these products. Morningglories (Ipomoea spp.) have traditionally been a difficult weed to control full season in corn making it problematic at harvest time. The objectives of this study were to determine the efficacy of HPPD-inhibitor products, with atrazine POST, or following atrazine PRE, and evaluate the differences for full-season morningglory control, particularly late season control. Additionally, we evaluated other broadleaf species that emerge in the field (Amaranthus spp. and Senna spp.) to determine which product(s) works best on each species. Traditionally, atrazine is added a preemergence treatment and an early-postemergence treatment to corn due to high efficacy and it’s low cost, though the atrazine PRE (1.12 kg ai ha-1) only treatment in this trial resulted in poor control. Morningglory control across all HPPD-inhibitor treatments was above 83% at 90 DAT. At harvest, control ranged from 75% to 94% across treatments applied POST with and without atrazine, with the exception of topramezone that resulted in 85% control with atrazine and 65% without atrazine at harvest. Additionally, tembotrione provided 75% and 70% control with and without atrazine, respectively. Amaranthus spp. were effectively suppressed until harvest with all HPPD-inhibitor treatments, with the exception of atrazine PRE alone that ranged from 74% 30 DAT to 60% control at harvest. A general decrease in control of Senna spp. was observed from 30 DAT to harvest, yet no treatments were statistically different. No statistical yield differences were recorded between HPPD-inhibitor treatments, as compared to the non-treated check.